in American Crayfish Electrotaxis and Phototaxis The ...eprints.ulm.ac.id/5942/1/Buku...

Mr. Ahmadi

The Feasibility ofElectrotaxis and Phototaxis

in American CrayfishImproved Experimental Designs

American crayfish Procambarus clarkii (Girard, 1852) has been supporting inone way, the aquaculture industry with remarkable commercial success inUSA and other countries because of its rapid growth and ecologicaltolerance. The other side, many countries have been regulating theintroduction of this invasive species due to their adverse impacts on thenative species and the ecosystems, including interference with fishingoperations and consumption of eggs of other fishes. In order to removethis exotic species, an effective low-cost harvesting method is needed. Thisbook, therefore, provides new ideas and synthesizes novel concepts whichimproved experimental designs in ascertaining the feasibility of eitherelectrotaxis or phototaxis of American crayfish. The detailed behavioralresponses and possible applications of the novel luring method are furtherdiscussed. This would be especially useful to the farmers and/orprofessionals in addressing the essential requirements for commercializingthe culture or developing environmental control measures of the species.

Dr.Ahmadi is a lecturer in the Faculty of Marine andFishery at Lambung Mangkurat University, Indonesia.He graduated from Kagoshima University, Japan. Hisresearch is focused on light fishing, fishing gearbehavior and shrimp behavior. He currently serves oneditorial committee for Journal of WetlandsEnvironmental Management under the University.

978-3-659-83015-0

i

CONTENTS

Contents i

Acknowledgments ii

List of Tables iii

List of Figures iv

Chapter 1 General Introduction 1

Chapter 2 Electrotaxis in the American Crayfish 5

2.1. Introduction 5

2.2. Materials and Methods 7

2.3. Results 12

2.4. Discussion 17

Chapter 3 Phototaxis in the American Crayfish 21

3.1. Feasibility Study 21

3.1.1. Introduction 21

3.1.2. Materials and Methods 22

3.1.3. Results 28

3.1.4. Discussion 34

3.2. Research based Development 37

3.2.1. Introduction 37

3.2.2. Materials and Methods 38

3.2.3. Results 41

3.2.4. Discussion 45

Chapter 4 Summary and Conclusions 49

References 52

ii

ACKNOWLEDGEMENTS

The author would like to thank the Ministry of Education, Science, Sports and Culture

of Japan for awarding me the scholarship to study in Japan (2002-2008). Thanks to the

Ministry of Marine Affairs and Fisheries, the Republic of Indonesia for recommending

me to get this scholarship. The author is immensely grateful to Professor Dr. Gunzo

Kawamura, my advisor, who accepted me as his student. He kindly guides and en-

courages me during all these years, which allowed me to finish this study and meet one

requirement for my PhD degree. I sincerely appreciate his personal care for me and my

family. Thank Professor Dr. Takeshi Kanda from Miyazaki University, my co-advisor

in the examination committee. My profound thanks for all the support received from

Associate Professor Dr Kazuhiko Anraku during my researches, from Associate Pro-

fessor Dr Takaaki Nishi for his valuable advice on the experimental designs, from Dr

Miguel Vazquez Archdale for his comments and reading the manuscripts of my re-

searches, from Ms Chitose Shinyama for any kind helps, from Mr. Masataka Marugi

and Mr. Souji Kodama for their technical assistance constructing the traps, and from

my friends Reza, Taro, Irene, Kenji, Kuno, Satoshi, Sasaki, Nakamura, Harold and all

the staff of the Faculty of Fisheries, Kagoshima University for their technical assis-

tance. The author also wishes to acknowledge the constructive criticism of the editorial

team of Lambert Academic Publishing.

iii

LIST OF TABLES

Table 1. Threshold voltage for the anodal orientation (I), movement (II),

and the most effective electric field that induced the highest

anodal group response, and electronarcosis in the American

crayfish…………………………………………….....................

17

Table 2. Magnitude of group response (mean % SE) in adults and ju-

veniles during the control periods………………………………

30

Table 3. Threshold light intensities and most effective light intensities

which induced highest positive phototaxis in adults and

juveniles………………………………………………………...

31

Table 4. Total number of catch in each trap treatment. Number of crayfish

in the pond was 400 and catches were released into the pond for

the next trial…………………………………………..................

32

Table 5. Data of the daily crayfish catches following different light con-

ditions in the pond experiments. The number of animal exam-

ined was 197 and release back into a pond after trials….............

44

Table 6. Number of crayfish caught by Incandescent light and LED light

traps from pond experiment…………………………………….

45

Table 7. Mean Standard Deviation of sizes for crayfish male and female

collected from incandescent light and LED light traps in the

pond experiments……………………………………………….

45

iv

LIST OF FIGURES

Figure 1. The American crayfish Procambarus clarkii (Girard, 1852)…. 4

Figure 2. Experimental apparatus for indoor (A) and outdoor (B)

experiments and electrode arrangements. E1, electrodes

placed standing on the bottom, no gaps from the tank walls;

E2, electrodes 5 cm above the bottom; E3, electrodes 10 cm

above the bottom; E4, small electrodes placed standing on the

bottom with gaps from the walls……………………………...

8

Figure 3. Electric field intensities measured in the indoor tank with

electrode arrangements E3 (side view) and E4 (top view).

Electric field intensities in the outdoor tank with electrode

arrangement E4 (top view)…………………………………...

9

Figure 4. Anodal group response (mean % S.E) under various electric

field intensities in the indoor tank with electrode arrangements

E1, E2, E3, and E4……………………………………………

13

Figure 5. Anodal group response (mean % S.E) under various electric

field intensities in the outdoor tank with electrode arrange-

ments E1, E2, and E4. Left panels show anodal movement;

right panels show crayfish that crawled away from the electric

field beyond the anode……………………………………….

16

Figure 6. Experimental apparatuses for the indoor experiments. A: a

PVC tank used for adults and juveniles; B: a glass tank used

for the second post-embryonic of crayfish. The dashed lines at

the center of the tanks indicate where the partitions were

placed. A flashlight is placed at left or right end sides of

tanks…………………………………………………………..

23

Figure 7. Traps used during the trapping experiments. Four box-shaped

traps were constructed with 6-mm iron frames (60 cm long by

50 cm wide by 25 cm height) and black 1.5 cm hexagonal

mesh wire (16 gauge PVC-coated wires). They had four large

entry funnels located on each side of the trap with a 6 cm in-

v

side ring entrance. A trap door (48 25 cm) on the top allowed

removal of the catch…………………………………………..

27

Figure 8. Group response (mean % SE) of adults and juveniles to the

lights during the control (C) without light and at different light

intensities both in the absence (opened squares) and the

presence of shelters (filled squares)………………………….

29

Figure 9. Group response (mean % SE) of the second post-embryonic

crayfish during the control (C) without light and at different

light intensities both in the absence (opened squares) and the

presence of shelters (filled squares)…………………………..

31

Figure 10. Mean carapace length and range of male crayfish captured by

traps in first to fourth experiments…………………………...

34

Figure 11. A: American crayfish Procambarus clarkii; B: laboratory tank

experiment; C: typical trap used in the pond; and D: typical

lamps used in laboratory and pond experiments……...............

39

Figure 12. Positive group responses (mean % SE) of crayfish when

exposed to incandescent lights (A) and LED lights (B) with or

without shelters. Left bars with grey area show strong re-

sponse of the animals towards the lamps and right bars show

weak response. There were significant differences between

control (a) and tests (b, c, d, or e) at *p<0.05;

**p<0.01………………………………………………………

42

1

CHAPTER 1

GENERAL INTRODUCTION

This study aimed to ascertain the feasibility of either electrotaxis or phototaxis of

American crayfish Procambarus clarkii (Girard, 1852) (Fig. 1), and to introduce

simple luring methods that can be employed for the control or eradication programs.

This species is commercially exploited in USA and other countries, but it is considered

a pest in Japan.

Crayfish are the largest mobile invertebrates inhabiting freshwaters. There are

about 500 known species of freshwater crayfish worldwide. The majority lives in

North and Central America, about 100 in the southern hemisphere, 4 in Asia and 5 in

Europe (Hobbs, 1988; Westman, 2002). Crayfish Astacopsis gouldi (Clark, 1936) is

the largest crayfish from Australia, reaching over 4.5 kg in weight (Holdich, 2002).

Crayfish are known by many names, from crawfish to stonecrab. Colors vary from a

light cream color through yellow, blue, red and green to black. Over 90 percent of

crayfish cultured in the United States are either red swamp crayfish P. clarkii (Girard,

1852) or white river crayfish P. acutus (Girard, 1852). The other important species are

the signal crayfish Pacifastacus leniusculus (Dana, 1852), the paper shell crayfish

Orconectes immunis (Hagen, 1870), the green pond crayfish O. nais (Faxon, 1885) and

the northern crayfish O. virilis (Hagen, 1870). All these species are captured from

streams, lakes and ponds as a "wild" crop. P. clarkii is most prominent crayfish not

only in U.S. but also remarkable commerical success in China (Huner, 1998) and

Spain (Ackefors, 1999) due to the rapid growth and ecological tolerance (Huner and

Lindqvist, 1995). However, many states have regulations prohibiting the introduction

of invasive species due to frequently have adverse impacts on native species and

ecosystems. This includes damage by burrowing, damage to rice plants, nuisance to

anglers, interference with fishing (e.g. eating fish from nets and other gear) and con-

sumption of fish eggs (Maitland et al, 2001; Westman, 2002).

2

The habitats of crayfish vary, but they prefer areas with some cover such as rocks

in streams or dense vegetation in lakes and ponds. They need structure for protection,

preventive against cannibalistic behavior during molting or hiding place from preda-

tors. The presence of vegetation in crayfish ponds will increase survival and produc-

tion (Goyert and Avault, 1978; Witzig et al., 1983). Crayfish are most abundant in

seasonally flooded wetlands (Huner and Barr, 1991). While crayfish abundance in

lakes and streams is more likely to be limited by predation and substratum availability

than by food supply (Garvey et al., 1994; Nystrom et al.,2006).

In all parts of the world, many active and passive gears are being used to collect

crayfish from ponds, rivers, lakes and streams. They are seines (D’ Abramo and Ni-

quette, 1991), electro-trawls (Cain and Avault, 1983), hand-netting (Rabeni et al.,

1997; Reeve, 2004), spoon net (Nakata et al., 2006), electrofishing (Westman et al.,

1978; Alonso, 2001; Ribbens and Graham, 2004), flat-bottomed boat (Huner and Barr,

1991; Romaire, 1995), quadrat sampler (Lamontagne and Rasmussen, 1993), diver

collections (Usio et al., 2007), throw-trap (Dorn et al., 2005), baited traps (Huner and

Barr, 1991; Romaire, 1995; Faller et al., 2006), baited sacks (Reeve, 2004),

sex-pheromone-baited traps (Stebbing et al., 2004), unbaited cylindrical eel nets

(Habsburgo Lorena, 1983; Gaude, 1986), fyke-nets (Holdich and Domaniewski, 1999;

Balik et al., 2005), and light traps are demonstrated in the present study (Chapter 3).

Catch is influenced by many factors, primarily water temperature and the density

of marketable crayfish. Other factors are water quality, type and quantity of vegetative

forage, weather, mass molting, lunar phase, cold fronts and harvesting intensity

(Romaire et al., 2004). P. clarkii reaches sexual mature at a size between 5.5 and 12.5

cm total length (Huner and Romaire, 1979). They should be harvested soon after they

reach marketable size. Consumers prefer a count of 23 individuals per pound and

larger (i.e., 3½ inches and larger). Large crawfish, 10 to 15 counts per pound usually

command premium price (Romaire et al., 2004).

Crayfish production can be divided into two distinct segments: hard-shell and

soft-shell production (Huner, 1990; Huner and Romaire, 1990). Hard-shell producers

3

market tail meat, similar to shrimp production, while soft-shell producers market the

entire body, similar to soft-shell crab production. Soft-shell crayfish are commercially

collected either for seafood industry (Culley and Duobinis-Gray, 1990) or fish-bait

industry (Maronek, 1994). In the 1980’s soft-shell crawfish were picked manually

from the pond harvested stock (Cain and Avault, 1983). The farmers also capture

hard-shell crayfish (e.g. baited trap) from wild populations or aquaculture ponds and

transport them to an indoor tank. The premolt individuals are identified and moved to

separate molting tanks where they are completely safe from the intermolt crayfish

(Culley et al., 1985). Other methods like injection of molting hormones, limb removal

and bilateral eyestalk ablation can be adopted to speed up the crayfish molting cycle

(Huner and Avault, 1977). Recently soft-shell crayfish can also be collected with the

lighted traps, which are not uncommonly established in the field conditions.

Basically, there are three crayfish species inhibiting lakes and rivers in Japan. The

Japanese crayfish Cambaroides japonicus (De Haan, 1841) is the only native repre-

sentative (Miyake, 1982), and two American crayfish: P. clarkii and Pacifastacus le-

niusculus are originally imported from North America between 1926 to 1930 (Kawai

et al., 2002). Both P. clarkii and P. leniusculus are regarded as aggressive species

because they have larger body and chelae size (Westman, 2002). C. japonicus lives in

cold, clear brooks and lakes in northern Japan including Hokkaido, Aomori, Akita and

Iwate Prefectures. It has no tolerance against high water temperatures and begins to be

affected by thermal shock above 20C and dies above 25 C (Nakata et al., 2002). In

the past, this species has been used as food for haute cuisine (Kurohagi, 1991).

However, uncontrolled spreading of two alien species is a considerable risk for C.

japonicus in habitats, shelter competition or mutual predation (Usio et al., 2007). As a

result, natural populations of C. japonicus have drastically declined, prompting the

Japanese Fisheries Agency in 1998 and the Environment Agency in 2000 to declare it

as an endangered species, and necessitating the collection of information for its con-

servation.

4

Generally, P. clarkii is considered a warm water species, whereas Pacifastacus

leniusculus is considered a cool water species (Henttonen and Hun er, 1999) as well as

C. japonicus. P. clarkii commonly lives in central and southern Japan. It is also found

in some habitats in Hokkaido with water temperature is above 25C in summer and

18C in mid-winter (Nakata et al., 2001). P. leniusculus can survive in the shelters

over three winter months with lowest temperatures about minus 20°C (Kozak and

Polizar, 2003) and highly tolerance up to 31.1C (Nakata et al., 2002). Recently Na-

kata et al. (2006) uncommonly found the coexistence of these alien species in the

Daini-Suzuran River, eastern Hokkaido, due to a hot spring flows into the river. P.

leniusculus can rapidly spread after invasions because of its high reproductive ability

(Nakata et al., 2004). Its distribution rapidly extended to other lakes and rivers in

Fukushima, Nagano and Shiga Prefectures of Honshu (Nakatani and Yokohama, 2003;

Usio et al., 2007). In Hokkaido, crayfish control has been started from 2006 to 2007

using the baited traps or by hand with the aid of SCUBA equipment (Usio et al., 2007),

but it is highly cost, long-term harvest and labour-intensive. The present study pro-

vides established and new possible harvesting methods to control the spread of

American crayfish through the investigation on electrotaxis and phototaxis.

Fig 1. The American crayfish Procambarus clarkii (Girard, 1852) used in the experiments

5

CHAPTER 2

ELECTROTAXIS IN THE AMERICAN CRAYFISH

2.1. Introduction

In Japan, the introduction of exotic species such as the American crayfish Pro-

cambarus clarkii (Girard, 1852) as live feed for the edible frog Rana catesbeiana

(Shaw, 1802) that was cultivated in rice fields has had adverse ecological effects on the

Japanese crayfish Cambaroides japonicus (De Haan, 1841) by competing with them

for habitat, shelters and resources (Saito and Hiruta, 1995; Usio, et al., 2001; Nakata et

al., 2006) and has caused economic losses to rice farmers by damaging the crop and

the dikes in paddy fields. In order to remove this exotic species, an effective low-cost

harvesting method is needed.

At the same time, a new harvesting method is needed by the crayfish aquaculture

industry. The crayfish after all is an important aquaculture commodity in many coun-

tries, though not in Japan, and supports a large industry in Louisiana, USA. Currently,

crayfish are harvested by professional trappers who receive about half of the gross

revenue, but there are not enough trappers during the peak harvest season (Cain and

Avault, 1983; Huner and Barr, 1991; Romaire, 1995). The baits used for the traps are

expensive, need freezing, and must be cut into small pieces. Another problem is that

low temperatures reduce the activity of the crayfish and they are no longer attracted to

the baits.

The shrimp industry in Japan has developed a variety of electric shockers, one of

which is attached to a drag net that is pulled over the pond bottom and forces shrimp to

leap out of the sand substrate and into the net (Shigueno, 1975). Similar methods have

been used in other crustacean fisheries (Pease and Seidel, 1967; Ko et al., 1972; Saila

and Williams, 1972; Stewart, 1975; Seidel and Watson, 1978; Fievet et al., 1996; Polet

et al., 2005). All these methods relied on electric stimulation of the shrimp’s body that

results in a strong contraction of the abdomen and forces the shrimp out of the burrow

or hiding place and into a net. Researchers in Louisiana developed a prototype electric

6

push net as an alternative harvesting method for crayfish (Cain and Avault, 1983) but

there are no reports on its commercial use. Electricity has been used to control the

movement of diseased crayfish Aphanomyses astaci (Schikora, 1906) in Sweden or

Arizona, and to exclude them from certain areas by means of electrical barriers (Un-

estam et al., 1972; Soderhall et al., 1977; Hyatt, 2004). Electrofishing is also being

used as a removal method for the possible eradication of the American signal crayfish

Pacifastacus leniusculus (Dana, 1852) from rivers (Sinclair and Ribbens, 1999; Reeve,

2004; Ribbens and Graham, 2004).

A direct electric current (DC) is a preferred type of current because it has the least

potential to harm individual fish (Lamarque, 1990; Beaumont et al., 2002; Snyder,

2003). When exposed to a DC current, fish tend to assume a position parallel to the

electric field, with their heads pointing toward the anode, and swim in the direction of

that electrode; this behavior is known as electrotaxis or galvanotaxis, and is used to

catch fish (Bary, 1956; Klima, 1972; Lamarque, 1990).

Some crustaceans also exhibit similar directional responses in a DC field. A strong

electrical stimulation causes the contraction of the abdominal muscles of crustaceans,

and this involuntary movement forces the animal either up off the bottom, or in the

direction of the anode. Higman (1956) showed that pink grooved shrimp Penaeus

duorarum (Burkenroad, 1939) in a seawater tank flicked their tails toward the anode

when subjected to an electrical field of pulsed DC. Westman et al. (1978) conducted

sampling for the European crayfish Astacus astacus (Linnaeus, 1758) by means of

non-pulsating DC and reported that the crayfish moved toward the anode by either

swimming backward with rapid tail flicks, or by crawling slowly forward out of their

hiding places. The Australian spiny lobster Panulirus cygnus (George, 1962) was

sensitive to the polarity of the electric field and either faced or propelled itself towards

the anode (Philips and Scolaro, 1980). The American lobster Homarus americanus

(Milne-Edwards, 1837) exhibited true electrotaxis in a pulsed DC electric field, where

it was compelled to swim to the anode (Koeller and Crowell, 1998). The brown shrimp

Crangon crangon (Linnaues, 1758) reacts strongly to the anode of pulsed DC (Polet et

7

al., 2005). However, Saila and Williams (1972) observed no electrotaxis but only tail

flick in the American lobster subjected to DC. In the Norway lobster Nephrops

norvegicus (Linnaeus, 1758), an electric field induced avoidance behaviour but no

electrotaxis (Stewart, 1974; Newland and Neil, 1990). Thus electrotaxis in crustaceans

is still questionable, and the different results may have been due to the different ar-

rangements of the electrodes in the various experimental designs.

We conducted this study to obtain detailed information on the behavioral responses

of the American crayfish to various DC electric stimuli, which could be applied to

develop economical harvesting and eradication methods for this species.

2.2. Materials and Methods

A. Indoor Experiment

For the indoor experiment, 10 American crayfish (42–48 mm carapace length and

85–98 mm body length), were obtained from a local supplier. They were kept in a 240

L PVC tank with tap water and an undergravel filter at 28°C and fed twice a week with

crayfish pellets (Japan Pet Drugs, Tokyo). For the outdoor experiment, five laborato-

ry-reared crayfish (34–37 mm carapace length and 72–87 mm body length) were used.

Individuals were used repeatedly within the same experiment. The crayfish were

handled according to methods prescribed by the Kagoshima University’s Guide for the

Care and Use of Laboratory Animals.

The indoor experiment was done at the Laboratory of Fishing Technology, Faculty

of Fisheries, Kagoshima University during June–July 2005. A polyvinyl chloride

(PVC) tank (190 × 42 × 40 cm) was used with a sand substrate bottom (2.5 cm thick)

and an undergravel filter system (Nisso, Tokyo), and filled with 240 L of tap water (30

cm deep) (Fig. 2A). The tank was divided into five equal zones (each zone 38 × 42 ×

40 cm): anode zone, middle zone, cathode zone, and both end zones beyond the elec-

tric fields (Fig. 2). Water temperature during the experiments was 28.0° C, and the

conductivity of water was 625 S cm-1

determined with a conductivity meter (YSI-85,

YSI Inc., USA).

8

Two types of electrodes were adopted: large stainless steel plate electrodes (40 cm

wide, 30 cm high, 1.0 mm thick), and small ones (20 cm wide, 18 cm high, 0.8 mm

thick). Electrical characteristic were sensed with a pair of pickup probe made from 3

mm diameter bronze rods spaced 10 cm and insulated so only the bottom 5 mm of each

rod was exposed. In the first experiment, the two large electrodes, an anode and a

cathode, were placed in the tank, upright on the bottom 114 cm apart and completely

partitioning its long axis by placing two PVC partitions (arrangement E1, Fig. 2).

Movements of the crayfish were restricted within the space between the electrodes. In

the second and third experiments, the large electrodes were raised 5 cm or 10 cm above

the bottom (E2 and E3). In the fourth experiment, the small electrodes were placed

upright on the bottom (E4). Since there were gaps, the crayfish were able to go out of

the electric field beyond the electrodes.

Fig. 2. Experimental apparatus for indoor (A) and outdoor (B) experiments and electrode arrangements. E1, electrodes

placed standing on the bottom, no gaps from the tank walls; E2, electrodes 5 cm above the bottom; E3, electrodes

10 cm above the bottom; E4, small electrodes placed standing on the bottom with gaps from the walls.

9

The DC electric stimulus was produced by a specially made electric converter-

stimulator (Hitachi, Tokyo). By adjusting the voltage of the electric converter- stim-

ulator, the voltage gradient applied on the crayfish was varied from 0.02 to 0.46 V cm-1

.

Voltage gradients were created by alternately reversing the polarity of the electrodes.

The electric field intensity was measured with an electric tester (Custom Corp.

CDM-2000D, Tokyo) throughout the tank to determine the voltage gradients at dif-

ferent locations. The signal was displayed on an oscilloscope (Iwatsu SS-5704, Tokyo)

for accurate measurements. The electrodes were periodically cleaned to prevent

measurement error caused by the gas bubbles on their surfaces.

Fig. 3. Electric field intensities measured in the indoor tank with electrode arrangements E3 (side view) and E4 (top view).

Electric field intensities in the outdoor tank with electrode arrangement E4 (top view).

10

Figure 3 shows the electric field intensities in the experimental tanks, especially

between electrodes arrangement E3 and E4. A uniform electrical field intensity was

present in the E1 arrangement (0.46 V cm-1

). In the E2 arrangement, the intensity at the

5 cm gap off the bottom was 0.46 V cm-1

, equal to that at the center between the

electrodes. In E3, the intensity was 0.44 V cm-1

at the gap 10 cm off the bottom. With

the small electrodes in E4, the intensities at the lower part of the electrodes (0.49 V

cm-1

) and close to the tank walls (0.48 V cm-1

) were higher than at the center between

the electrodes (0.46 V cm-1

). A small electric field was detected behind the electrodes

but it was near zero, with the wave forms on the oscilloscope fluctuating between 0.01

and 0.09 Volts.

The crayfish were exposed to electric stimuli in the form of voltage gradients at

intensities ranging from 0.02 to 0.46 V cm-1

. The group of 10 crayfish was used in

every trial, and 5 trials were done at each voltage gradient intensity. The total number

of trials at different voltage gradients was 115. The animals were given time to recover

after each trial: 2 min after trials with 0.02–0.10 V cm-1

; 3 min after 0.12–0.20 V cm-1

;

4 min after 0.22–0.30 V cm-1

; and 5 minutes after 0.32–0.46 V cm-1

.

Before each trial, the crayfish were confined in the middle zone of the tank by

means of two PVC partitions. At the start of each trial was the control period, when the

partitions were removed and the crayfish were allowed to move freely for 1 min. Then

the partitions were put back in place and the crayfish confined again in the middle zone.

The test consisted of removing the partitions and applying the voltage gradient for 1

min. During the control and test periods, the movements and numbers of crayfish were

carefully noted every 15 s in the three zones in arrangement E1, or five zones in E2, E3,

and E4.

Any movement of a crayfish toward the anode upon stimulation was considered a

positive response, whether or not the crayfish reached the anode within the 1 min test

period. For quantitative analysis of the response to the electric field, the magnitude of

anodal group response (%) was defined for each trial by the following formula:

11

Magnitude of anodal group response (%) = No. of crayfish with positive response

No. of crayfish in test 100

The percent values for 5 trials at each voltage gradient were compared statistically

with the percent values for the controls by the Mann-Whitney test (Conover, 1980).

When the test values were significantly higher than the control value, the group re-

sponse was considered positive.

B. Outdoor experiment

An outdoor experiment was conducted outside the laboratory on February 2007 in a

fiber-reinforced plastic oval tank (214 × 169 cm; Tanaka-Sanjiro, Fukuoka, Japan)

with 1,700 L tap water (47 cm deep), and a 1.5 cm deep sand bottom (Fig. 2B). Due to

the low water temperature, an electric heater (Nisso, Tokyo) was used. Water temper-

ature during experiments varied from 12.5–17.0°C and the water conductivity was

80–160 S cm-1

. The electrodes and electrical apparatus were the same as in the indoor

experiment.

The average electric field intensities between the large electrodes (E1 and E2) were

the same as in the indoor tank. Between the small electrodes (Fig. 3-E4), intensities

were 0.46 V cm-1

at the center, 0.45 V cm-1

at 10 cm from the edge, and 0.43 V cm-1

beyond the electrodes.

Before the electric stimulation, the crayfish were confined in a plastic mesh box at

the middle zone of the tank. The control, test exposure, data collection, and analysis

were carried out the same way as in the indoor experiment.

We determined two threshold voltages: threshold voltage I, which induced parallel

orientation of the animal to the electric field and forward crawling toward the anode,

and threshold voltage II, which induced flicking of the tail and backward swimming

toward the anode.

12

2.3. Results

A. Indoor experiment

Figure 4 shows the results of the indoor experiments with the electrode arrange-

ments E1–E4. During the control period (0 V cm-1

) in the experiment when the

electrodes were placed upright on the bottom (arrangement E1), the crayfish moved

their appendages (claws, walking legs, swimmerets, antennas, antennules, and

mouthparts) normally and walked freely throughout the three zones, while their bodies

oriented at random. The anodal control group response was only 184.9% (mean

percent standard error).

When a stimulus of 0.02 V cm-1

was applied, the crayfish showed a slight twitch of

the walking legs and antennas, indicating the detection of the electric field. At 0.06 V

cm-1

(threshold voltage I), two crayfish in five trials exhibited a clear parallel orienta-

tion to the electric field facing the anode, but the anodal group response was the same

as the control (183.5). The Mann-Whitney test showed that the percentage re-

mained at the same level of the control at 0.02–0.08 V cm-1

(p>0.05). At 0.10 V cm-1

or

higher, the percentage was significantly higher (p<0.05) than in the control. At

0.12–0.14 V cm-1

(threshold voltage II), the crayfish showed the tail flick, due to

contraction of the abdomen, and swam backward toward the anode.

At 0.16 to 0.30 V cm-1

, movement of claws, walking legs, swimmerets, tail fan, and

antennae became more pronounced. This was followed by reorientation of the crayfish

to face the cathode, then the onset of the involuntary tail flick, and a resultant move-

ment toward the anode. The maximum anodal group response (774.2%) toward the

anode was elicited by electrical intensity of 0.24 V cm-1

(Fig. 4, E1).

At 0.32–0.46 V cm-1

, the crayfish exhibited abnormal behavior such as unbalanced

walking, extreme tail flick, and lying on their dorsal side. Two to four of 10 crayfish

showed the tail flick, twitched their tail fans rapidly, swam backward only a short

distance, and then sometimes lay on their dorsal side. When the electric current was

switched on at high voltages (0.40–0.46 V cm-1

), the crayfish jerked their tail, then laid

motionless on their dorsal side and stayed in that position for several seconds or

13

minutes after the current had been switched off. If the crayfish moved again, there was

no orientation. Lying on the back with muscular rigidity was a sign of narcosis, and

3–5 crayfish were affected during the different trials at high electrical intensity.

Fig. 4. Anodal group response (mean % S.E) under various electric field intensities in the indoor tank with electrode

arrangements E1, E2, E3, and E4.

In the experiments with the electrodes 5 cm (E2) or 10 cm (E3) off the bottom, the

crayfish during the control period freely crawled around, and some passed under the

electrodes; the anodal group response was 206.3. There was no change in behavior

at 0.02–0.04 V cm-1

, only that 3–4 crayfish walked slowly to both the anode and

cathode zones, and then left the electric field through the gaps under the electrodes.

The Mann-Whitney test showed that the percentage was significantly higher (p<0.05)

than the control at 0.04 V cm-1

in the E2 arrangement and at 0.06 V cm-1

in E3; these

were thus the threshold voltage Is.

14

At 0.12–0.16 V cm-1

, the animals raised one or both claws facing the cathode and

slowly moved backward, or walked around the anode zone and then passed beneath the

anode out of the electric field; this was threshold voltage II.

At 0.18–0.32 V cm-1

, 6–8 crayfish swam backward with rapid tail flicks, or swam

rapidly forward with their abdomen and tail fan elevated and both claws raised, then

left the electric field. Two to four animals moved for a short distance or settled on the

bottom facing the anode.

High positive anodal group responses (793.9) (p<0.05) were obtained at

0.20–0.26 V cm-1

in E2 and at 0.20–0.24 V cm-1

in E3 (Fig. 4, E2 and E3). Thus, about

80% of the crayfish tested showed the same tendency to crawl away from the cathode

toward the anode and under the anode out of the electric field. This result suggests that

the crayfish were not attracted by the anode, but just repelled by the cathode. Over-

stimulation occurred at 0.34–0.46 V cm-1

, and crayfish behaved as if narcotized.

In the experiment with the small electrode arrangement E4, the crayfish moved

almost the same way as described above, but they crawled away from the electric field

through the gaps between the electrodes and the walls (164.0%). At 0.02–0.08 V cm-1

,

only 2–3 crayfish crawled slowly out of the electric field, and the others crawled

around in the anode or the cathode zones. Sometimes the crayfish stayed right next to

the electrodes, or climbed the anode without being shocked. The Mann-Whitney test

showed that the percentage was significantly higher (p<0.05) than the control at 0.10 V

cm-1

(threshold voltage I), and swam backward toward the anode by flicking their tails

at 0.14–0.16 V cm-1

(threshold voltage II).

At 0.18–0.30 V cm-1

, the crayfish quickly swam forward between the electrodes

and the tank walls out of the electric field; swam sideways crossing the electric field;

or swam backward with rapid tail flicks toward the anode. The maximum anodal group

response (727.3) (p<0.05) occurred at 0.30 V cm-1

(Fig. 4, E4). Overstimulation at

0.32–0.46 V cm-1

also narcotized the crayfish.

15

B. Outdoor experiment

Figure 5 shows the results of the outdoor experiment with three electrode ar-

rangements (E1, E2, E4). In the experiment with the electrodes upright on the bottom

(Fig. 5, E1), the crayfish in the control period moved slowly at a low water temperature

of 12.5°C, and moved faster when water temperature was raised to 13.5°C. The group

anodal response during the control period was 276.7. With stimulation at 0.02–0.06

V cm-1

, the group anodal response was the same as the control. The Mann-Whitney test

showed that the group response at 0.08 V cm-1

(threshold voltage I) was significantly

higher (p<0.05) than the control. The animals swam back toward the anode by flicking

their tails at 0.14–0.16 V cm-1

(threshold voltage II). High positive anodal group re-

sponse (6011.5%) was obtained at 0.24 V cm-1

.

At 0.28 V cm-1

or higher, the crayfish struggled and could not remain upright. Two

crayfish lay narcotized in the anode zone. Beyond the electric field at 10 cm, crayfish

were still affected by the electric current and crawled sideways or turned and moved

back away from the electric field. Farther from the field, they crawled along the side of

the tank or settled their bodies on the bottom.

With electrodes 5 cm over the bottom (Fig. 5, E2), the crayfish during the control

period stayed in the center zone or moved to the cathode zone, but none moved into the

anode zone. At 0.04 V cm-1

(threshold voltage I), four crayfish in three trials clearly

oriented parallel to the electric field and faced the anode. Below 0.10 V cm-1

, about

67–73% of the crayfish crawled away from the electric field beyond the anode. At

0.12–0.14 V cm-1

(threshold voltage II), the crayfish flicked their tails and swam back

toward the anode. Stimulation at 0.16 V cm-1

induced (6713.3%) of the animals to

move toward the anode, but higher intensities of 0.20–0.26 V cm-1

induced only

(5312.4) to do so. Electronarcosis set in at 0.28 V cm-1

. Beyond the electric field, the

crayfish crawled freely around the tank or rested on the bottom. These results again

showed that crayfish were not attracted to the anode, but avoided the cathode and tried

to escape the electric field.

16

Fig. 5. Anodal group response (mean % S.E) under various electric field intensities in the outdoor tank with electrode

arrangements E1, E2, and E4. Left panels show anodal movement; right panels show crayfish that crawled away

from the electric field beyond the anode.

With the small electrodes (Fig. 5, E4), the anodal group response in the control

period was 78.0%. The percentage was significantly higher (p<0.05) than the control

at 0.08 V cm-1

(threshold voltage I). Half of the crayfish (476.7%) moved toward the

anode and crawled away from the electric field beyond the anode. The crayfish flicked

their tails and swam backward at 0.14 V cm-1

(threshold voltage II). A maximum an-

odal group response (6011.5%) occurred at 0.16 V cm-1

and declined with increasing

voltage. Two animals showed narcosis at the anode zone at 0.30–0.46 V cm-1

. These

results also suggested that crayfish were not attracted by the anode but repelled by the

cathode.

During the control periods, the crawling speeds of the crayfish were 1.95–2.60 cm

s-1

and they never swam backward. When stimulated at intensities ranging from

0.26–0.32 V cm-1

the crayfish swam backward toward the anode at speeds of

6.67–19.5 cm s-1

.

17

Table 1 summarizes the threshold voltages for the anodal orientation and move-

ment, most effective electric field intensity and electronarcosis in the crayfish.

Threshold I ranged 0.04–0.10 V cm-1

and threshold II 0.12–0.16 V cm-1

. The most

effective electric field intensity that induced anodal group response was 0.24–0.30 V

cm-1

, when the conductivity of water was 625 S cm-1

in the indoor tank at 28.0° C,

and was 0.16–0.24 V cm-1

, when the conductivity was 80–160 S cm-1

in the outdoor

tank at 12.5–17.0° C. Electronarcosis set in between 0.32 and 0.46 V cm-1

in the indoor

tank, and between 0.28 and 0.46 V cm-1

in the outdoor tank. The crayfish recovered

from electronarcosis several minutes after the electric current had been switched off.

Table 1. Threshold voltage for the anodal orientation (I), movement (II), and the most effective

electric field that induced the highest anodal group response, and electronarcosis in the

American crayfish.

Test tank

(Water temper-

ature)

Arrangement of electrodes

Threshold voltage

(V cm-1

)

Most effective

electric field

(V cm-1

)

Electro

narcosis

(V cm-1

) I II

Indoor tank

(28.0°C) Electrodes upright on the bottom (E1) 0.06 0.12 – 0.14 0.24 0.32

Electrodes 5 cm off the bottom (E2) 0.04 0.12 – 0.16 0.26 0.34


Small electrodes (E4) 0.10 0.14 – 0.16 0.30 0.32

Outdoor tank

(12.5–17.0°C) Electrodes upright on the bottom (E1) 0.08 0.14 – 0.16 0.24 0.28


Small electrodes (E4) 0.08 0.14 0.16 0.30

2.4. Discussion

This study clearly demonstrated in the tank experiment that in a uniform electric

field, the American crayfish were sensitive to the electric field and showed a slight

twitch of the walking legs indicating detection of the weak electric field at 0.02 V cm-1

.

Crayfish within moderate electric fields of 0.12–0.30 V cm-1

showed positive elec-

trotaxis or movement toward the anode. In the E1 electrode arrangement (upright on

the bottom), the crayfish oriented to the anode, flicked the tail, moved toward the

anode, and continuously flicked the tail after reaching the anode. However, in the E2

18

and E3 electrode arrangements (5 and 10 cm over the bottom), the crayfish moved to

the anode and crawled beyond it out of the electric field. Such movement beyond the

anode cannot be explained as positive electrotaxis and can be interpreted as repulsion

from the cathode.

The forward crawling and the backward swimming shown by the crayfish in the

present study have also been documented earlier in the pink shrimp Penaeus duorarum

(Higman, 1956; Kessler, 1965), the European crayfish Astacus astacus (Westman et al.,

1978), the Norway lobster Nephrops norvegicus (Stewart, 1974), the Australian spiny

lobster Panulirus cygnus (Phillips and Scolaro, 1980), American lobster Homarus

americanus (Koeller and Crowell, 1998), American crayfish Procambarus clarkii

(Kawai et al. 2004) and the brown shrimp Crangon crangon (Polet et al., 2005).

In our study, we determined threshold voltage I (0.04–0.10 V cm-1

), which induced

parallel orientation of the animal to the electric field and forward crawling toward the

anode, and threshold voltage II (0.12–0.16 V cm-1

), which induced flicking of the tail

and backward swimming toward the anode (Table 1). The threshold voltage did not

vary with water temperature in this study. Kessler (1965) reported that threshold

voltages in the pink shrimp were affected by water temperature where the shrimp

tested at 14°C and 36°C had higher mean threshold voltages than shrimp tested at 20°C

and 28°C. The threshold voltage I of 0.04–0.06 V cm-1

for the freshwater crayfish in

our study was similar to that of the pink shrimp Penaeus duorarum (0.06 V cm-1

) from

coastal waters and estuaries (Kessler, 1965), despite the fact that the conductivity of

sea water is roughly 1,000 times that of freshwater.

The most effective electric field intensity that induced anodal group response in the

American crayfish was higher in the indoor tank (0.24–0.30 V cm-1

) than in the out-

door tank (0.16–0.24 V cm-1

) (Table 1). This was attributable to the conductivity of tap

water, which was affected by temperature. The more ions, the more conductive the

water resulting in a higher electrical current. The conductivity was 625 S cm-1

at 28

C in the indoor tank and 80–160 S cm-1

at 12.5–17.0 C in the outdoor tank.

19

Orientation of the animal in an electric field is an important factor in inducing

anodal movements. The American crayfish required a threshold voltage for anodal

movement that was 1.4 times higher when they faced the cathode than when they faced

the anode. Fish required more voltage to respond when facing the anode than when

facing the cathode (Klima, 1972). The pink shrimp required about twice as much

voltage when facing the cathode than when facing the anode (Kessler, 1965). Wathne

(1967) reported that shrimp responded much more readily when their body axis was

perpendicular to the electrodes than when they were parallel to them. Klima (1968)

concluded that the voltage felt by shrimp varies not only with its orientation but also

with its total length. Meanwhile, larger shrimp had lower thresholds than smaller

shrimp (Kessler, 1965).

Within strong electric fields, animals are stunned (electronarcosis), injured or

killed. However, American crayfish that suffered electronarcosis for 5 min at 0.46 V

cm-1

quickly recovered within 1 min without any ill effect or injury (and regardless of

water temperature 12.5–28.0° C). At extreme field strengths of more than 20 V cm-1

, it

was possible to cause Australian spiny lobsters to lose their legs, but no lobsters were

ever killed (Phillips and Scolaro, 1980). The European crayfish Astacus astacus

(Westman et al., 1978) or the white-clawed crayfish, Austropotamobius pallipes

(Lereboullet, 1858) (Alonso, 2001) collected by electric fishing often have no claws.

Smaller crayfish are more prone to suffer cheliped loss. It should also be noted that

voltage output used in this work is remarkably lower than that employed in other

studies, which typically ranges between 3–7 V cm-1

(e.g. Westman et al., 1978;

Penczak and Rodriguez, 1990; Fievet, 1996; Bernardo et al., 1997).

Knowledge of the change in behavior of crayfish with intensity of the electric field

can be applied to control and catch them during electric fishing. The most effective

electric field intensity (0.16–0.30 V cm-1

) that induces anodal group response can be

used to herd crayfish to a trap or net. This intensity must be carefully adjusted to

prevent electronarcosis, which occurs at just a little higher intensity, 0.28–0.34 V cm-1

.

When crayfish are insensible in a high electric field, they have to be collected imme-

20

diately before they recover from the narcosis. This requires work and time for the

fishers. Although the adjustment is not easy, the difficulty might be overcome by im-

provement in the fishing skill.

For eradication, we can learn from previous studies (e.g. Ribbens and Graham,

2004; Reeve, 2004) using electrofishing for removal which appeared successful in

catching all age classes of American crayfish; however, to eliminate them completely

is impractical. This work is only effective in shallow creeks, wet seeded rice fields or

small ponds, and only catches a limited portion of the crayfish population; therefore, it

is not a viable method of control. Electric fishing over fish’s spawning areas should be

avoided. Any captured indigenous crayfish species or other aquatic organisms should

also be humanely released.

21

CHAPTER 3

PHOTOTAXIS IN THE AMERICAN CRAYFISH

3.1. Feasibility Study

3.1.1. Introduction

The American crayfish Procambarus clarkii (Girard, 1852) is an important aqua-

culture commodity in the United States (Huner and Barr, 1991; Romaire, 1995), China

(Huner, 1998a), Spain (Ackefors, 1999) and other countries. They are also invasive

pests in several countries where they have been introduced. In Japan, the American

crayfish and signal crayfish Pacifastacus leniusculus (Dana, 1852) have had adverse

ecological effects on the indigenous crayfish Cambaroides japonicus (De Haan, 1841)

by competing with them for habitat, shelters and resources (Saito and Hiruta, 1995;

Usio et al., 2001; Nakata and Goshima, 2003; Nakata et al., 2006), thus economically

feasible eradication methods need to be developed.

Several active and passive fishing methods are being used to harvest crayfish, e.g.,

seines (Huner, 1994), trawls (Faulkner and Huner, 1994), fyke-nets (Balik et al., 2005)

and baited traps (Bean and Huner, 1979; Huner, 1998b; McClain et al., 1998). The use

of seines and dragged nets or trawls is ineffective in vegetated ponds (D’Abramo and

Niquette, 1991). Electrofishing equipment however, improved the fishing efficiency of

dip nets or trawls in vegetated ponds (D’Abramo and Niquette, 1991), and the nature

of the electrotaxis in the American crayfish was demonstrated (Ahmadi et al., 2008).

In the past, North American crayfish (genera Astacus and Cambarus) were often

caught at night by lighting a fire near a lake or river bank to lure them to the shore

(Chidester, 1912). Westman et al. (1978) used gas-lamps or battery-fed car-headlights

when sampling the European crayfish Astacus astacus (Linnaeus, 1758). While Kozak

et al. (2007) examined the light intensity preferences of the American crayfish.

Experimentally, the range of light intensities that produces behavioral response in the

crayfish is still poorly understood. Fernández-de-Miguel and Aréchiga (1992) exam-

ined the effect of placing a white light bulb above a chamber containing P. clarkii and

22

showed that they were positively phototactic to low light intensities (0.17–1.4 1x), but

negatively phototactic to higher intensities (above 5.6 lx). Kozak et al. (2007) reported

that the American crayfish showed positively phototactic response to strong light at

1,000 lx. Thus, the information on the phototactic response in the American crayfish is

inconsistent.

The trials in collecting crayfish using lights through laboratory and pond experi-

ments, has established the magnitude of group responses of crayfish towards different

intensity of incandescent lamps or different color of LED lamps. Specifically, the pond

trials were considered crucial in addressing the essential requirements for commer-

cializing the culture or developing environmental control measures of the species.

3.1.2. Materials and Methods

A. Laboratory experiment

The objective of this laboratory experiment was to examine phototactic responses

of P. clarkii towards different intensities of 4.5 W flashlights in a PVC tank. The in-

door experiments were conducted in the Fishing Technology Laboratory of the Faculty

of Fisheries, Kagoshima University from June to November 2006.

Two groups of P. clarkii, cultured and wild, were used in the indoor experiments.

Crayfish (N=64) were grouped according to age and size into three developmental

stages following established criteria (Sukô, 1953) as follows: (1) cultured adults

(N=10) and wild ones (N=10), sexually mature and measuring 55 mm or more in total

length; (2) cultured juveniles (N=10) and wild ones (N=14), 1–3 months old and less

than 33.9 mm total length; and (3) the second post-embryonic crayfish (N=20), 10–14

days old and less than 11.8 mm total length. Adult animals were obtained from local

suppliers, while juvenile and the second post-embryonic animals were hatched and

reared at our laboratory. Individuals were used repeatedly within the same experiment.

Prior to the observations, each adult and juvenile was marked on the dorsal carapace

with a water-proof white marker for easy identification. Adults or juveniles were kept

in a 240 L polyvinyl chloride (PVC) tank (190 × 42 × 40 cm) filled with tap water (30

23

cm deep) at 24.5–28 C. The tank had a sand substrate at the bottom (2.5 cm thick) and

water quality was maintained with an undergravel filter (Fig. 6A). The crayfish at the

second post-embryonic stage were kept in a 15.5 L glass tank (60 × 21.5 × 19 cm)

filled with tap water (12 cm deep) at 16–20 C and no sand substrate (Fig. 6B). Dis-

solved oxygen concentration was 4.8 mg L-1

, as determined with a DO meter (YSI 85,

YSI Inc., USA). The animals were fed twice a week with commercial crayfish pellets

(Japan Pet Drugs, Tokyo) at 0.5 % of their body weight.

Post-molt crayfish also were examined for phototactic renponses in the same tank

and light conditions as those used for adults and juveniles. They were 42 juveniles and

16 adults either the newly molted or several hours after the molt.

The crayfish were handled according to the methods prescribed by Kagoshima

University’s Guide for the Care and Use of Laboratory Animals.

Fig. 6. Experimental apparatuses for the indoor experiments. A: a PVC tank used for adults and juveniles; B: a glass tank

used for the second post-embryonic of crayfish. The dashed lines at the center of the tanks indicate where the

partitions were placed. A flashlight is placed at left or right end sides of the tanks.

The tanks were placed inside a box-shaped black velvet chamber (2.8 × 1.5 × 1.75

m) to avoid the interference of external light and to prevent other disturbances. Out-

side-light could still penetrate through the black velvet resulting in dim light, but no

adverse effect was observed on the animals because most of them remained motionless.

During the night, a ceiling lamp (384 W) was switched on to give a similar ambient

24

light environment during the day. All experiments were conducted with the same light

presentations, both in the absence and the presence of shelters in the tanks. For adults

and juveniles, the shelters were made of PVC pipe pieces (4.8 cm diameter, 15 cm

long), while for the second post-embryonic crayfish the shelters used were artificial

water plants.

A 4.5 W flashlight was used as a light source. The light intensity was varied with 1

to 10 white-paper filters, and the light intensity at 5 cm away from the lamps was de-

termined with an illuminometer (IM-2D, Topcon Ltd., Japan). The light intensity

ranged from 46 to 1,290 lx. The flashlight was placed 5 cm from the left or right side

along the axis of the tank wall, in line with the animals inside tank. To avoid shadows

or the reflection of the light beam at the opposite side of the tank wall, a reversible

black screen was used. This screen was painted with glossless black paint and placed at

the opposite end of the light inside the tank wall.

Observations of the movements of the crayfish before and after the onset of light

were made both during day and night. The duration of the light stimulus at the re-

spective intensities was 5 min in 5 trials with the adult or juvenile, and 5 min in 3 trials

with the second post-embryonic crayfish; this included the reversal of the light source

from one side of the tank to the other. The crayfish were given 2 min rest time after

each trial. To observe the crayfish in the dark, a 1.5 W dimmed-flashlight was used for

2–3 seconds from the side of tank wall, which did not appear to affect crayfish be-

havior.

Before each trial, adults or juveniles were confined between the center and the dark

area of the tank with a PVC partition, thus providing them with enough space for free

crawling. At the start of each trial was a control period of 5 min, when the partition was

removed and the crayfish were allowed to move freely. Then the partition was returned

to its original place and the crayfish confined again. The trial consisted of stabilizing

light for 15 s by putting a black partition in front of light source, removing the partition

and applying the light stimulus for 5 min at a particular intensity. The second

post-embryonic stage of crayfish was confined to the center of the tank with two PVC

25

partitions placed 13 cm apart. The experimental procedure was the same as those used

for adults and juveniles.

Movements of the animals during the stimulation in each trial were observed for

5-min (test period) and recorded with a digital video camera (Sony DCR-TRV18,

Tokyo). Directional crawling towards the light source within the 5-min test period was

considered a positive response. Movement of the animal by crawling away from the

light during the stimulation and staying in the dark area for a long period of time (5–25

min) was defined as negative response.

For the quantitative analysis of the response to the light, magnitude of group re-

sponse (GR) (%) was defined for each trial by the following formula for adults or

juveniles:

Magnitude of GR = No.of Cp

No.of crayfish in test 100

For the second post-embryonic crayfish:

Magnitude of GR = No.of Cp – No.of Cn

No.of crayfish in test 100

Where Cp is crayfish showing positive response and Cn is crayfish showing negative

response.

The percent values from 5 trials at each light intensity were statistically compared

with the percent in the control period using the Mann-Whitney test (Conover, 1980).

When the test values were positive and they were significantly higher than the control

value, the group response was considered positive. When the test values were negative

and they were significantly higher than the control value, the group response was

considered negative. Threshold intensities for positive or negative responses were

determined at the 5% level.

26

B. Trapping experiment

The objective of trapping experiment was to examine mechanism of phototaxis in

P. clarkii following different methods of trapping. Trapping experiments were con-

ducted during the night at the Faculty of Fisheries, Kagoshima University from July to

November 2007.

Four hundred adult crayfish (31–57 mm carapace length) with a sex ratio of 1:1

male to female were obtained from local suppliers and used in this study. They were

kept in 3,200 L concrete fish pond (10.0 5.8 0.7 m) with tap water (55 cm deep) at

18.5–29.5°C. They were fed twice a week with the kuruma shrimp pellet food (Hi-

gashimaru, Kagoshima, Japan) at a feeding ratio of 0.5–1% of their body weight.

Water grass Hydrilla verticillata and zooplankton were introduced into the pond and

kept as natural dietary items for the crayfish. A polyethylene net and a blue plastic

sheet were placed above the pond to reduce solar radiation and to inhibit unwanted

algae growth. Shelters made of PVC pipe pieces (approx. 15 cm long and 6 cm di-

ameter) were placed in the pond. Aeration was applied for 24-hour. Water tempera-

ture.Dissolved oxygen was 5.7–6.7 mg L-1

, measured with a DO meter (YSI 85, YSI

Inc., USA).

Four box-shaped traps were constructed with the same dimensions and materials

(Fig. 7). They were lighted, dimmed, baited and non baited traps. For lighted and

dimmed traps, a 4.5 W lamp was placed inside a waterproof acrylic box (14 8 15

cm) and attached to the center of the trap base. For the dimmed lamp, white-paper was

used to line the walls of the box. Light intensity of both lamps was 2,050 and 1,010 lx

at 5 cm away from the lamps. Turbidity of the pond water was 1–15 FTU (Formazin

turbidity unit) determined with a spectrophotometer (DR-2000, HACH, USA).

27

Fig. 7. Traps used during the trapping experiments. Four box-shaped traps were constructed with 6-mm iron frames (60

cm long by 50 cm wide by 25 cm height) and black 1.5 cm hexagonal mesh wire (16 gauge PVC-coated wires).

They had four large entry funnels located on each side of the trap with a 6 cm inside ring entrance. A trap door (48

× 25 cm) on the top allowed removal of the catch.

For the baited trap, a piece of the Pacific mackerel Scomber japonicus (33–60 g)

was placed in a wire bait container (14 6 cm) between the funnel entrances. The bait

that remained after retrieving the trap was reweighed to find the actual amount of bait

consumed. The non-baited trap served as a control.

The traps were set at random positions at sunset and retrieved next morning. The

soaking time varied from 12-14 hours. At the retrieval of the traps, the crayfish in the

traps were checked for sex, carapace length, body length, chelipeds length, weight and

released back into the pond. During night, the behavior of the animals around the traps

was observed using the 1.5 W flashlight which did not disturb the behavior of the

crayfish. Total number of trapping trials was 35, consisting of 4 trials in the first ex-

periment (lighted and dimmed traps), 10 trials in the second experiment (all trap types)

and 10 trials in the third experiment (lighted, dimmed and non baited traps) and 11

trials in the fourth experiment (a follow-up of the third experiment where the amount

of aeration was increased).

28

For the statistical analysis, the Mann-Whitney test was employed to compare the

catches between the lighted and dimmed traps at the 5% level in the first experiment.

The Kruskal-Wallis test was used in the second, third and fourth experiments to ex-

amine the differences between the traps. The Multiple Comparison test was conducted

to see which catch differed among the traps.

3.1.3. Results

A. Laboratory experiments

In the laboratory experiments, adults and juveniles showed a positive group pho-

toresponse regardless they were wild or cultured, and the magnitude of the group re-

sponse tended to increase with light intensity (Fig. 8). In the dark in daytime (daytime

dark) and in the dark in nighttime (nighttime dark), most of the adults and juveniles

tended to remain motionless during the control period, the control group response

ranged between 1 1.4% (mean % ± SE) and 10 4.5% (Table 2).

During the test periods in the daytime dark, adults and juveniles exhibited typical

photopositive responses towards the light source and showed higher magnitude of

group response in the absence of shelters than in the presence of shelters

(Mann-Whitney test, p<0.05). The threshold light intensities determined for adults and

juveniles are shown in Table 2. The lowest threshold was 46 lx for juveniles in the

presence of shelter in the nighttime dark, and the highest threshold was 659 lx in the

presence of shelter in daytime dark. Any consistent tendency between the daytime and

nighttime darks and between adults and juveniles were not detected since the threshold

largely varied, and was not determined for the adults in nighttime dark due to low

magnitude of group response during the test periods. The magnitude of group response

was significantly higher during the daytime dark than nighttime dark (Mann-Whitney

test, p<0.01).

29

Fig. 8. Group response (mean % (C) without light and at

different light intensities both in the absence (opened squares) and the presence of shelters (filled squares).

Both in daytime and nighttime darks, adults and juvenile tended to exhibit higher

magnitude of group response at higher light intensities especially in the absence of

shelters. At 1,290 lx (the highest intensity tested), the cultured and wild adults crawled

about the tank or moved to the light source, reached the light source in less than one

minute (24–57 s) at different starting points from the light source (100–185 cm). The

Gro

up

re

sp

on

se

(%

)

Light intensity (lx)

Cultured juvenile Wild juvenile

Cultured adult Wild adult

DAYTIME

NIGHTTIME

DAYTIME

NIGHTIME



20

40

60

80

250 500 750 1000 12501500 250 500 750 1000 1250 1500

20

40

60

80

20

40

60

80

C

20

40

60

80

C

Gro

up

re

sp

on

se

(%

)




DAYTIME

NIGHTTIME

DAYTIME

NIGHTIME



20

40

60

80

250 500 750 1000 12501500 250 500 750 1000 1250 1500

20

40

60

80

20

40

60

80

C

20

40

60

80

C

30

highest mean magnitude of group response during the daytime was 70 4.5% at 866 lx

for cultured juveniles and 60 4.8% at 1,290 lx for cultured adults (Fig.8). The highest

light intensity induced highest positive group response and was most attractive for

adults and juveniles (Table 3). The positive photoresponses in the absence of shelters

were significantly higher (p<0.01) than with the presence of shelters most of the time.

Response to the lights was significantly higher (p<0.01) during the daytime dark than

nighttime dark, and proportionally increased with light intensities. Cultured juveniles

were more attracted to the lights than wild ones.

Table 2. Magnitude of group response (mean % SE) in adults and juveniles during the control

periods.

Crayfish

Magnitude of control group response (%)

Daytime Nighttime

Without shelter With shelter Without shelter With shelter

Cultured adult 6 2.4 6 4.0 8 3.7 4 8.9

Wild adult 4 2.4 4 2.4 10 4.5 6 2.4

Cultured juvenile 6 4.0 4 2.0 4 2.4 2 2.0

Wild juvenile 7 2.3 3 2.9 3 1.8 1 1.4

In the second post-embryonic crayfish, they often gathered at the center of the tank

but tended to move against the light source position and the mean magnitude of the

control group response was negative; from -14 4.3% to -10 2% in the daytime dark

and from -21 2.9% to -4 2.4% in the nighttime dark (Fig. 9). During the test periods

in the daytime dark, they showed typical negative phototactic responses at high light

intensities and the magnitude of group response fluctuated between -30 5.7% and -39

6.9%. In the daytime dark, the threshold light intensity for the negative phototaxis

was determined as 111 lx both in the presence and absence of shelters. In the nighttime

dark, on the other hand, they did not exhibit strong phototactic response and the

threshold light intensity was determined only in the presence of shelter as 46 lx.

31

Fig. 9. Group response (mean % ± SE) of the second post-embryonic crayfish during the control (C) without light and at

different light intensities both in the absence (opened squares) and the presence of shelters (filled squares).

Post-molt juveniles and adults tended to crawl away from the light and to remain in

the dark for several hours after molt. They behaved negatively phototactic when

stimulated at 461–1,290 lx, and showed a little or no further response at lower inten-

sities. In the presence of shelters, only three animals hid inside shelters for a long pe-

riod of time.

Table 3. Threshold light intensities and most effective light intensities which induced highest posi-

tive phototaxis in adults and juveniles.

Crayfish

Threshold light intensities (lx) Most effective light intensities (lx)

No shelter Shelter present No shelter Shelter present

Daytime Nighttime Daytime Nighttime Daytime Nighttime Daytime Nighttime

Cultured adult 312 *** *** *** 1,290 1,290 1,290 1,290

Wild adult 111 *** 58 *** 1,290 1,080 1,080-1,290 1,290

Cultured juvenile 46 46 58 46 1,290 1,290 866-1,290 866-1,290

Wild juvenile 190 *** 659 46 1,290 1,290 866-1,290 1,290

*** , threshold is not determined.

DAYTIME

-50

-40

-30

-20

-10

0200 400 600 800 1000 1200 1400

Gro

up

re

sp

on

se

(%

)

NIGHTTIME

-50

-40

-30

-20

-10

0

200 400 600 800 1000 1200 1400


C

C

DAYTIME

-50

-40

-30

-20

-10

0200 400 600 800 1000 1200 1400

Gro

up

re

sp

on

se

(%

)

NIGHTTIME

-50

-40

-30

-20

-10

0

200 400 600 800 1000 1200 1400


C

C

32

B. Trapping experiment

The results of the trapping experiment sequences are summarized in Table 4. In the

first experiment with the lighted and dimmed traps, the crayfish crawled toward the

traps and searched for the funnel entrances. They climbed and crawled on the traps and

held to the netting, but most of them remained motionless outside the trap while facing

the light. Inside the traps, the animals crawled around, flicked their tails when they

encountered each other or elevated their postures in front of the light. There were no

significant differences in the total catch between the two trap treatments (Mann

Whitney test, p>0.05).

Table 4. Total number of catch in each trap treatment. Number of crayfish in the pond was 400 and

catches were released into the pond for the next trial.

Experiment

(water temperature)

No. of

trials Traps

Catch

Male Female Total

I

(28.0 - 29.5°C)

4 Lighted 33 36 69

Dimmed 35 27 62

II

(29.0 - 28.0°C)

10 Lighted 22 (1) 11 33 b

Dimmed 20 15 35 b

Baited 111 (4) 68 179 ** a

Non-baited 19 (1) 11 30 b

III

(28.5 - 26.0°C)

10 Lighted 50(4) 43 (4) 93 ** a

Dimmed 26 25 51 * b

Non-baited 23 7 30 c

IV

26.5 - 18.5°C

11 Lighted 21 22 43

Dimmed 32 12 44

Non-baited 25 10 35

Total 417(10) 287(4) 704

- Significantly different between a, b and c. * P<0.05;

** P<0.01

- The bracketed numbers indicate number of post-molt crayfish (1–2 days after molt).

In the second experiment with the lighted, dimmed, baited and non-baited traps,

when the baited trap was lowered to the bottom of the pond, the animals approached

the baited entrance by crawling. They struggled to touch the bait by inserting claws

and legs through the bait container. In the first day of trials, when no pellet food was

33

given, the catch in the baited trap increased rapidly during the first hours after setting

the trap, the bait was soon consumed and 47 crayfish were caught. On the following

days, when the animals were daily fed with pellets, the catch in the baited trap re-

markably declined to 10–21/day. The bait attractiveness also decreased, the crayfish

consumed 18 to 45 % of fish bait given indicating that most crayfish were still satiated.

The effect of this feeding frequency was followed by a decreasing catch in the other

traps (3–4 in the average per tap). During the day, they were also voraciously con-

suming the water grass present in the pond. Inside the trap, they crawled along the base

of the trap, climbed and held onto the netting or fought with each other. These be-

haviors were also observed in the crayfish caught in the non-baited trap. The baited

trap captured a significantly larger number of crayfish than the other three traps

(Multiple comparison test, p<0.01), and there were no significant difference in catches

between the lighted, dimmed and non-baited traps (Kruskal-Wallis test, p>0.05).

In the third experiment, the performance of lighted and dimmed traps was com-

pared with that of a non-baited trap. There were significant differences in the total

catch between the three traps (Kruskal-Wallis test, p<0.05), and the lighted and

dimmed traps captured significant larger number of crayfish than the non-baited trap

(Multiple comparison test, p<0.05).

In the fourth experiment with lighted, dimmed and non-baited traps, the water

temperature largely decreased from 26.5 to 18.5°C, the crayfish remained active (3–4

in the average catch per trap a day) and were attracted to the lights, but were not as

active as they were in warmer water. There were no significant differences in the total

catch between the three traps (Kruskal-Wallis test, p>0.05), even the amount of aera-

tion was increased.

The sex ratio of the catch from 35 night trials was remarkably biased to male; 417

males, including 10 post-molt crayfish with a soft-shell, and 287 females including 4

post-molt crayfish (Table 4). Among these 14 soft-shell crayfish, 9 were from the

lighted trap, 4 from the baited trap, and 1 from the non-baited trap. We collected empty

carapaces of 45 crayfish besides these soft-shell crayfish, but it was difficult to

34

determine the exact molting ratio.

The size of crayfish captured ranged from 24 to 58 mm in carapace length and

there were no significant differences between catches from respective four traps

(p>0.05) (Fig. 10).

Fig. 10. Mean carapace length (mm) and range of male crayfish captured by traps in first to fourth experiments.

3.1.4. Discussion

Our tank experiments show that the positive phototactic response is much more

intense in the daytime dark than in the nighttime dark. However, it has long been

known that the American crayfish are nocturnal animals and that the levels of general

locomotor activity are much greater during the night than during the day (Page and

Larimer, 1972; Gherardi et al., 2000). Crayfish emerge from diurnal hidings (e.g.

rocks in streams or dense vegetation in lakes and ponds) at night to forage for food or

to avoid predation (Hill and Lodge, 1994; Garvey et al., 1994). The daytime dark

might be an unusual light condition for the crayfish which have never experienced it.

35

40

45

50

55

I II III IV

Experiments

Cara

pa

ce

le

ng

th (

mm

)

Lighted trap

Dimmed trap

Baited trap

Non-baited trap25

30

20

60

35

40

45

50

55

I II III IV

Experiments

Cara

pa

ce

le

ng

th (

mm

)

Lighted trap

Dimmed trap

Baited trap

Non-baited trap25

30

20

60

35

Although the positive group response largely fluctuated in the present study, it is

evident that the juvenile and adult American crayfish are positively phototactic and

can be allured into a trap equipped with a lamp. The positive phototaxis became more

prominent with increasing light intensity in the laboratory, but the trapping unex-

pectedly showed no differences in catch between lighted and dimmed traps. The light

intensity of the dimmed trap was 1,010 lx which was only half of that of lighted trap

2,050 lx. The difference in the light intensity might not be large enough to cause a

different catch and both lights were attractive enough to allure the crayfish into the

traps in the pond.

In the trapping experiments, many more males were captured than females in all

type traps while the sex ratio of the population was 1:1 in the pond (Table 4). Such

male dominant catch is also reported for Astacus leptodactylus (Eschscholtz, 1823)

from fyke-nets in a lake (Balik et al., 2005), the signal crayfish Pacifastacus lenius-

culus (Dana, 1852) or the white-claws crayfish Austropotamobius pallipes (Lere-

boullet, 1858) or the noble crayfish Astacus astacus (Linnaeus, 1758) from baited traps

in rivers (Reeve, 2004; Gallagher et al., 2005; Faller et al., 2006), the rusty crayfish

Orconectes rusticus (Girard, 1852) or Orconectes virilis (Hagen, 1870) and Cambarus

bartoni (Fabricius, 1798) from baited traps in lakes (Somers and Green, 1993; Hein et

al., 2007). The fyke-net and trap are passive gears and their catch largely depends on

the activity of animals and competition between males and females. Molting crayfish

are less active especially females (Reynolds, 2002). Egg-bearing females are also less

active than males (Holdich, 2002). They become more active after releasing the young

and preparing for mating (Richards et al., 1996; Reeve, 2004; Faller et al., 2006).

According to this study, egg-bearing females can be allured into a lighted trap. Cray-

fish with larger chelae win competitive interactions for shelter (Capelli and Munjal,

1982). Male American crayfish have larger chelae than females of the same size and

males might inhibit females from entering traps. Perhaps this is why females com-

prised only 41% of total catch in the present study. Although the traps are male-biased

gear, female ratio in catch would increase when population density decreases and

36

competitive interactions are rare. According to Brown and Bowler (1977), female

“avoid” traps irrespective of reproduction state, so sex ratio does not always represent

the real situation within the population.

It is interesting to note that soft-shell crayfish were captured in the lighted trap. In

the laboratory we found post-molt crayfish within several hours after molt tended to

crawl away from the lights. When the crayfish molts, the eye functions less well due to

the old cornea becoming detached just before the molt, and this probably continues for

several hours until the new cornea hardens. The photonegative behavior during the

recovery time might be mediated by the caudal photoreceptor located in the 6th ab-

dominal ganglion. It is known that illumination of the tail produces tail flexion fol-

lowed by backward walking (Edwards, 1984). The capture of the soft-shell crayfish in

the lighted trap might indicate that the eye recovers its function soon after the molt and

then the crayfish become photopositive again.

The use of light is advantageous in harvesting post-molt crayfish. The post-molt

crayfish are not attracted to food or bait as they have no appetite for several days after

molt (Nakamura, 1980). The problem is associated with their mouth part and digestive

apparatus. As the foregut lining is shed, the gastroliths drop into the lumen of the

foregut where they are gradually broken down and their contents mostly resorbed by

the gut epithelium and the hepatopancreas (Travis, 1960). Body stores of calcium are

used to recalcify the mouthparts and foregut ossicles, so as to allow early resumption

of feeding (Chaisemartin, 1967). Taugbol et al. (1997) reported that remineralisation is

effectively almost complete within 2 to 4 days, although it probably continues very

slowly throughout the intermolt. The American crayfish show a feeding pattern closely

related to the molting cycle; starvation during molt and 2-3 days after molt, highly

active feeding for several days after the starvation, steep decrease in feeding activity

and a quite low food intake for several days before a next molt (Nakamura, 1980). The

use of baited traps might be effective only during the highly active feeding and a rel-

ative effectiveness of the lighted trap increases during the low feeding period. The

lighted trap has another advantage. Crayfish prey animals, such as insect larvae and

37

worms, may be attracted to the light and create a foraging opportunity for the crayfish

in the lighted traps.

While the baited trap is most effective among the four luring treatments, trapping

results indicate that when baited, lighted, non-baited traps are used, some crayfish

prefer bait, some prefer light and the others seek for a non-baited trap as a shelter.

Therefore, the use of lamp seems feasible for trapping adult and juvenile crayfish.

However, some other method is required to effectively capture second post-embryonic

crayfish which avoid light and are untrappable in lighted traps.

We recommend a use of combination of baited traps, lighted traps and some other

method developed for capturing post-embryonic crayfish. By this combination, the

invasive crayfish at different growth stages would be captured for its eradication.

3.2. Research Based Development

3.2.1. Introduction

American crayfish Procambarus clarkii is one of the most prominent species of

crayfish that supports in one way, the aquaculture industry with remarkable commer-

cial success, e.g. in Louisiana, USA (Romaire, 1995), Kenya (Olouch, 1990), China

(Huner, 1998), and in Spain (Ackefors, 1999) because of its rapid growth and eco-

logical tolerance (Huner and Lindqvist, 1995). Farmers in Louisiana produce soft-shell

crayfish not only for fish bait but also for the seafood industry (Culley and Duobin-

is-Gray, 1989), and provide egg-bearing females to aquafarmers for breeding purposes

(Richards et al., 1995). On the other hand, many countries have been regulating the

introduction of this invasive species due to their adverse impacts on the native species

and the ecosystems (Bernardo et al., 1997; Usio et al., 2001; Nakata et al., 2006), in-

cluding damages to substrates, especially to rice paddies due to their burrowing habit,

and interference with fishing operations and consumption of eggs of other fishes

(Maitland et al., 2001). Collecting crayfish from the wild and ponds makes use of

conventional gears (e.g. baited traps, fyke nets) but since this has been found to be

ineffective, the use of lights in trapping the crayfish is therefore being promoted to

38

improve the harvesting procedures and address the need to reduce the population of the

invasive crayfish.

The use of light emitting diode (LED) in fishing has been introduced in many

countries to optimize fish catch considering that fish and other aquatic species have

color receptions in their eyes that could recognize various intensities of light that lead

to their aggregation in lighted areas. The use of LED lights is one of the most recent

advances in light fishing being promoted in fisheries, instead of using incandescent,

halogen, and metal halide illuminations. In order to adapt the use of LED lights in

harvesting the American crayfish, their phototactic responses were tested using in-

candescent and LED lamps in laboratory experiments as well as in the pond trials.

3.2.2. Materials and Methods

A. Laboratory Experiment

The objective of this laboratory experiment was to examine phototactic response of

P. clarkii toward different intensities of incandescent lamps or different colours of

LED lamps in a PVC tank. The experiments were conducted in the Fishing Technology

Laboratory of Faculty of Fisheries, Kagoshima University, Japan in August 2007.

A series of experiments was conducted in PVC tank (190×42×40 cm) using 26

adult crayfish (109–151 mm total length) at 1:1 male to female sex ratio, and kept in

tank with tap water at 23-26.5C during 12 h light:12 h dark. The tank had sand sub-

strate at the bottom with an under-gravel filter system. The animals were fed twice a

week with crayfish pellets at 0.5 % body weight. Dissolved Oxygen (DO) concentra-

tion was 4.8 mg L-1

while turbidity of the water was 10 FTU.

In order to examine the phototactic responses of P. clarkii towards different light

intensities in the PVC tank, four incandescent lamps with different intensities were

used as light sources (Fig. 11). Light intensity of each lamp was 215 lx (SIL-1), 398 lx

(SIL-2), 1010 lx (DIM) and 2050 lx (LIGHT) where SIL-1 = 0.45 W and SIL-2 = 1.5

W measured in air using an illuminometer (IM-2D, Topcon, Ltd. Tokyo). SIL-1 (0.45

W) and SIL-2 (1.5 W) were Japanese squid fishing tackles (Yo-zuri Co. Ltd. Japan).

39

For DIM and LIGHT, 4.5 W lamp was placed inside a waterproof acrylic box

(14×8×15 cm), the walls of which were lined with white-paper, and 1 to 4 1.5 V bat-

teries. Meanwhile, four selected colours of LEDs (8 mm cylindrical package) were

used as light sources (Fig. 11) with each colour placed inside a lamp case of SIL-2

which was generated by 3 V dry-cell battery (0.06 W). The light intensity of LEDs was

set at equal quanta intensities by placing a grey fiberglass window screen inside each

lamp (Dio Chemicals, Ltd., Tokyo), and the spectral irradiance for each color was

determined using a spectroradiometer (HSR-8100, Maki Mfg., Japan).

Recapture experiments were car-

ried out at night before and after set-

ting the lamps under ambient light

environment. While the LED lamp

was placed downright to the bottom

anchored with a weight with the other

tip tied to a stationary rod, the in-

candescent lamps had weights placed

on top of the lamp to hold them in

upward pressure. Lights were stabi-

lized by caging the lamps with a piece

of PVC pipe (15 cm long and 4.8 cm

dia) for LED lights and a plastic mesh

box (18×18×20 cm) for the incan-

descent lamps for 30 sec before ex-

posing the animals to the lights.

Before each trial, the animals were confined to one end of the tank by a black PVC

partition, providing them with enough space for free crawling. At the start of each trial

a control with ambient light applied for 10 min, the partition was removed and the

animals were allowed to move freely. Then the partition was returned to its original

place confining the animals again. Put the partition in and out didn’t affect the crayfish

LIGHTDIMSIL-2SIL-1 BLUE GREEN YELLOW RED

B

C

D

A

Fig. 11: A: American crayfish P. clarkii; B: laboratory tank

experiment; C: typical trap used in the pond; and D: typical

lamps used in laboratory and pond experiments.

40

behavior was observed. The trials consisted of submerging the lamp, removing the

partition, applying the lamp for 10 min, and capturing crayfish with a scoop net. (see

Fig. 11). Shelters made from PVC pipe (approx. 15 cm long and 6 cm diameter) were

distributed at the bottom. Total number of trials was 20, of which 10 trials were with

shelters and the other 10 trials were without shelters, and incandescent or LED lamps

were applied by rotation. Each lamp was repeatedly used for 5 trials including the

reverse of a lamp from one side of tank to the other. The animals were given 10 min

rest time after each trial.

Movement of the animals during each trial was recorded with a digital video

camera (Sony DCR-TRV18, Tokyo), while the animal behavior in ambient light

(control) was observed by eyes. Directional crawling towards the light within the 10

min test period was considered a positive response. A strong positive response was

defined when the animals approached towards a lamp within 2 min and remained at

least 75 cm from the lamp’s radius. A weak positive response was considered if the

animals crawled slowly towards a lamp within 10 min per trial. When the animals

crawled away from the lamp and ceased in dark area for a long period of time (within

50 min) was defined as a negative response. The percent values for 5 trials at each

lamp were statistically compared with the percent for the control using the

Mann-Whitney test (Conover, 1980). When the test values were significantly higher

than the control value, the group response was considered positive. The test was

evaluated at the 0.05 level of significance.

B. Trapping Experiment

Trapping experiments were conducted at night in a concrete pond (10.05.80.7 m,

55 cm deep) using 197 adult crayfish (68-111 mm TL) with 1:1 male to female sex

ratio and kept in 3200 L tap water at 16-28C. The animals were fed twice a week with

commercial prawn feed at feeding ratio of 0.5-1.0% body weight. Shelters made of

PVC pipes (approx. 15 cm long and 6 cm dia) were distributed at the bottom, and

aeration was applied for 24 h; DO concentration was 6.65 mg L-1

while turbidity of

41

water ranged from 1 to 14.6 FTU.

Four box-shaped traps were constructed with 6-mm iron frames (60 cm x 50 cm x

25 cm) and black 3/5 inch hexagonal mesh wire (16 gauge PVC-coated wire). The

traps had four large entry funnels on each side with 6 cm inside ring entrance, with a

trap door on top (4825 cm) to release the animals (Fig. 11). The light sources were the

same as those used in laboratory experiments and were repeatedly used every night in

two pond experiments to test light intensity and light color preference.

The traps were lowered on the pond before sunset and retrieved the following

morning, with each trap set at a distance of roughly 4.5-8.5 m from each other fol-

lowing the pond shape and rotated each night, while soaking time varied from 13 to 14

h. The crayfish were counted when traps were hauled and checked for sex, carapace

length, body length, chelipeds length, weight, and released back into the pond. Of the

total 37 trials (148-trap hauls), 15 used incandescent light traps and 22 with LED light

traps. The Kruskal-Wallis test was used to see if there were significant differences in

the total catches of the four different trapping treatments. Then, Multiple Comparison

test was used to determine which catch differed significantly among the traps (Conover,

1980). All tests were evaluated at the 0.05 level of significance.

3.2.3. Results

A. Laboratory Experiment

Results from the control with ambient light indicated that most of the adults seemed

to remain motionless regardless of the shelters provided. Response of the control

group was between 3.15.0 (mean%SD) and 6.25.8 (Fig. 12A). During the trial

periods, the animals showed significant photopositive responses towards SIL-1

(26.97.7%) at 215 lx, SIL-2 (23.17.7%) at 398 lx, and LIGHT (13.86.4%) at 2050

lx (p<0.05). Most of the time, the crayfish exhibited higher magnitude of group re-

sponse in the absence of shelters than with shelters (p<0.01). Positive photo responses

were more pronounced in lower than in stronger light intensities (p<0.05), but the

magnitude of group responses declined significantly when shelters were employed.

42

Some animals only responded to the DIM (13.1 7.5%) at 1010 lx and SIL-1 (10.8

5.0%) at 215 lx (p<0.05). In all trials, most animals rested in the dark area while their

bodies were orienting to the light at random, i.e. animals hide in the shelters to be away

from strong light intensity (LIGHT) or were moulting during the trials.

In the second laboratory trial, the

control group response was between

3.15.0 (mean % SD) and 6.2

7.0 (Fig. 12B). When the animals

were exposed directly to colour LED

in the absence of shelters, the mag-

nitude of group responses was more

pronounced to green, blue and yel-

low lights (p<0.05) than that of the

control, but there was no significant

difference between the control and

red light (p>0.05). In the presence of

shelters, phototactic responses to-

wards green, yellow and red were

significantly higher (p<0.05) than

that of the control, but no significant

difference between the control and

blue (p>0.05).

Under light stimulation, the animals behaved similarly to each type of lamp, i.e.

spontaneously changed their positions by crawling forward along sidewall of the tank

while waving their chelipeds and antenna whips pausing near a lamp, moving for short

distances, or remaining motionless while facing the light. Some animals failed to reach

the lighted area when larger animals ambushed them, but the shelters appeared to be

helpful for the egg-bearing females. There were no significant differences in the at-

tractability of males and females in the tank experiments. Moreover, the duration of

5

15

25

35

5

15

25

35

5

15

25

35

45

5

15

25

35

45

A

B

Po

sit

ive

gro

up

re

sp

on

se

(%

)

CONTROL LIGHTDIMSIL-1 SIL-2

BLUE GREEN YELLOW REDCONTROL

With Shelters

Without Shelters

With Shelters

Without Shelters

**b**c

*ed

a

a

*bc

*d

e*c

*b **c

a

*b

**c

*d

e

**c

**e

*d

a

*e*b

Fig. 12. Positive group responses (mean % SE) of crayfish

when exposed to incandescent lights (A) and LED lights (B)

with or without shelters. Left bars with grey area show strong

response of the animals towards the lamps and right bars

show weak response. There were significant differences

between control (a) and tests (b, c, d, or e) at *p<0.05;

**p<0.01

43

animals’ concentration near a lamp seemed to be longer when the light was obscured

conforming to the lack of visual field of the animals.

B. Trapping Experiments

In the first pond experiment, crayfish in the pond were exposed to SIL-1, SIL-2,

Lighted and Dimmed light traps simultaneously. The animals crawled slowly towards

the lighted traps with or without waving their chelipeds while searching for the funnel

entrances. Inside the trap, the animals crawled around while holding on to the netting

or elevating their postures in front of a lamp. Outside the traps, some animals moved

around or crawled along the sidewall of the pond for some distances, but most re-

mained motionless while facing the lamps. Movement of the animals during each trial

in the pond was directly observed by ocular inspection. The average catch per trap per

night ranged between 1.3 0.5 and 7.5 2.4 (Table 5). The Kruskal-Wallis test

showed no significant differences in the total catch (Table 6) or in terms of average

sizes between males and females (Table 7). Despite the original 1:1 male to female sex

ratio in the pond, many more males were caught than females (sex ratio of 1.6:1.0,

Mann-Whitney test, p<0.05).

In the second pond experiment, the performance of blue, green, yellow and red

LED light traps were investigated simultaneously. While the animals behaved almost

the same as described in the above findings, behavior was difficult to observe during

the last 22 trials because of low water clarity. The average catch per trap per night

ranged between 1.0 0.8 and 7.0 0.8 (Table 5). The Kruskal-Wallis test showed no

significant differences in the total catch (Table 6) or in the average sizes between males

and females (Table 7). As in the first pond experiment, more males were significantly

caught in all LED light traps with sex ratio of 2:1 male to female (Mann-Whitney test,

p<0.01). In addition, 15 egg-bearing females were also observed although there were

no indications that they behaved differently than females without eggs.

44

Table 5. Data of the daily crayfish catches following different light conditions in the pond experi-

ments. The number of animal examined was 197 and release back into a pond after trials.

DATE NO

TRIAL

INCANDESCENT LIGHT TRAPS TOTAL MEAN ± SD

SIL-1 SIL-2 LIGHTED DIMMED

10-11Sep 2007 1 4 3 5 2 14 3.5 ± 1.3

11-12 1 1 5 7 3 16 4.0 ± 2.6

12-13 1 1 7 10 6 24 6.0 ± 3.7

13-14 1 3 3 4 5 15 3.8 ± 1.0

14-15 1 6 11 6 7 30 7.5 ± 2.4

15-16 1 4 4 4 6 18 4.5 ± 1.0

16-17 1 2 3 7 4 16 4.0 ± 2.2

17-18 1 2 7 7 4 20 5.0 ± 2.4

18-19 1 3 6 7 2 18 4.5 ± 2.4

19-20 1 6 2 3 6 17 4.3 ± 2.1

20-21 Oct 1 14 3 1 5 23 5.8 ± 5.7

21-22 1 2 2 16 5 25 6.3 ± 6.7

22-23 1 2 1 1 1 5 1.3 ± 0.5

23-24 1 11 1 0 1 13 3.3 ± 5.2

24-25 1 1 1 2 1 5 1.3 ± 0.5

Total 15 62 59 80 58 259 -

DATE NO

TRIAL

LED LIGHT TRAPS TOTAL MEAN ± SD

BLUE GREEN YELLOW RED

23-24 Sep 2007 1 8 7 6 7 28 7.0 ± 0.8

24-25 1 6 7 2 10 25 6.3 ± 3.3

25-26 1 1 5 11 8 25 6.3 ± 4.3

26-27 1 5 4 5 6 20 5.0 ± 0.8

27-28 1 3 1 4 2 10 2.5 ± 1.3

28-29 1 3 4 2 7 16 4.0 ± 2.2

29-30 1 3 3 4 2 12 3.0 ± 0.8

30 Sep-1 Oct 1 4 1 5 5 15 3.8 ± 1.9

1-2 1 2 9 4 7 22 5.5 ± 3.1

2-3 1 4 4 3 5 16 4.0 ± 0.8

4-5 1 7 2 8 6 23 5.8 ± 2.6

5-6 1 6 4 3 5 18 4.5 ± 1.3

6-7 1 4 0 1 3 8 2.0 ± 1.8

7-8 1 1 3 2 16 22 5.5 ± 7.0

8-9 1 1 6 4 7 18 4.5 ± 2.6

15-16 1 3 1 2 1 7 1.8 ± 1.0

16-17 1 1 4 1 5 11 2.8 ± 2.1

17-18 1 1 3 1 3 8 2.0 ± 1.2

18-19 1 11 0 3 3 17 4.3 ± 4.7

19-20 1 2 3 4 8 17 4.3 ± 2.6

25-26 1 1 1 0 2 4 1.0 ± 0.8

26-27 1 1 15 4 0 20 5.0 ± 6.9

Total 22 78 87 79 118 362 -

45

Table 6. Number of crayfish caught by Incandescent light and LED light traps from pond experiment.

Experiments

(Water Temp.) Traps

No. of

hauls

Catch

Male Female Total Missing

claw(s)

Regenerating

claw(s)

Carrying

eggs

PondExp 1 Incandescent

(16.0-28.0 C) Lighted 15 44 36 80 5 2 2

Dimmed 15 43 15 58 1 0 1

SIL-1 15 39 23 62 0 1 2

SIL-2 15 34 25 59 2 1 1

PondExp 2 LED

(18.0-27.5 C) Blue 22 61 17 78 3 4 0

Green 22 60 27 87 5 6 3

Yellow 22 46 33 79 1 6 1

Red 22 77 41 118 4 8 5

Total - 148 404** 217 621 21 28 15

Significant differences between male and female: * p<0.05;

** p<0.01

Table 7. Mean Standard Deviation of sizes for crayfish male and female collected from incandescent

light and LED light traps in the pond experiments.

Pon-

dExp. Traps Male Female

CL BL ChL BW CL BL ChL BW

1 Incandescent

Lighted 45.9±4.9 91.0±8.5 91.3±13.3 27.3±8.4 45.7±4.1 92.2±8.3 73.2±9.4 24.7±7.1

Dimmed 46.2±4.0 92.0±7.1 88.0±7.0 24.8±5.6 46.5±3.8 93.5±7.7 76.5±9.2 26.1±8.2

SIL-1 49.4±4.1 96.6±7.3 98.6±7.3 33.1±9.2 47.1±4.4 95.1±8.3 76.3±9.4 26.8±8.0

SIL-2 44.6±3.5 88.8±6.3 84.6±9.1 24.0±4.9 46.1±4.4 92.7±8.3 73.9±9.7 25.2±5.8

2 LED

Blue 46.7±4.0 92.8±7.3 92.2±10.8 28.3±7.1 45.7±3.6 92.5±7.0 73.7±6.7 24.9±5.7

Green 45.9±3.7 91.3±6.8 90.1±12.3 26.8±6.3 47.1±3.7 95.2±7.2 75.3±9.1 26.0±6.0

Yellow 46.5±4.2 92.5±7.3 91.5±11.3 28.2±8.0 48.6±3.3 97.6±6.6 77.7±9.0 28.1±5.5

Red 46.5±3.5 92.1±6.0 90.5±12.0 26.9±6.0 47.2±4.4 95.0±8.5 76.0±10.1 26.7±7.2

CL: carapace length; BL: body length; ChL: cheliped length; BW: body weight

3.2.4. Discussion

Results from the pond experiments seem not to support the findings from the la-

boratory experiments indicating the possible effect of the size of the tank. The dif-

ference between the light intensity in small tank and large tank may be significant to

the animal. Moreover, although the light intensity of LED was set at equal quanta in-

tensities in air, the intensity may not be the same in water because of the waters’ dif-

ferent levels of absorption of light wavelengths (colors). Therefore, it could not be

established whether the color or light intensity of LED affects the difference in “at-

46

traction”, which is still arguable as with the findings of Marchetti et al. (2004) in using

chemical light sticks for collecting fish larvae.

Nevertheless, the trials strengthened the findings of a previous research that P.

clarkii have true positive phototaxis (Ahmadi et al., 2008), while the form and optical

characteristics of lamps used in this trials were able to attract crayfish into the traps. In

this regard, the use of Japanese squid fishing tackle (SIL-1, 0.45 W) with diamond

shape on its surface was considered unique as it can increase the distribution of the

amount of lights and showed an equal effective to the acrylic box lamp (LIGHT, 4.5

W) in the catch ability. Whenever Japanese squid fishing tackles are applied in turbid

water the use of higher intensities is recommended and the results are still open for

discussion.

The total number of 362 crayfish taken from the pond using selected LED light

traps (Table 5) was sufficient enough to support previous studies that P. clarkii have

multicromatic visual system between blue and red (Nosaki, 1969; Cummins and

Goldsmith, 1981) or have true color vision (Kong and Goldsmith, 1977), that enables

the crayfish to alter independently their behavior responses to different colors, con-

sidering that true color discrimination is only possible when an animal has at least two

receptor types with distinct but overlapping spectral ranges. Color discrimination re-

quires inputs of different photoreceptor cells that are sensitive to different wavelengths

of light. Anatomically, P. clarkii possessed two photosensitive systems, one of which

is their sensitivity to blue light developed in their early life stage and the other, is

sensitivity to red light which is developed later (Fanjul-Moles and Fuentes-Pardo,

1988; Fanjul-Moles et al., 1992), implying that the photosensitivity of crayfish

changed in their different life stages. The physiology of vision of P. clarkii has been

generally well documented, e.g. the formation of retina and eyestalk in P. clarkii was

described by Hafner and Tokarski (1998), while the primary structure of their photo

pigment was described further by Hariyama et al. (1993). Although their vision has

been widely studied, their behavioral responses to different intensities or colors under

47

field conditions (e.g. stream, lake, wild paddy field) are lacking, and future research on

this aspect is strongly underlined.

Moreover, the movements and behaviours of P. clarkii in indoor tanks under light

are still poorly described. While Fernández-de-Miguel and Aréchiga (1992) reported

on the attraction and withdrawal responses as important adaptive mechanisms in

crayfish, Fanjul-Moles et al. (1998) paid more attention on the effect of variation in

photoperiod and light intensity towards survival and behavior in crayfish. While

Kozak et al. (2009) devoted to the assessment of light intensity preferences, only the

“light source directional behavior” was described in detail but not the “exploratory

behavior”, where exploratory behavior is defined as the animal directing its body

towards the object surrounding it then roving around the tank at a certain distance, with

or without lights, looking for ‘something’. Presumably, when refuge/shelter and cer-

tain conditions of lights were provided, the animals are likely to crawl inside/under the

shelter and stop moving. However, adding shelters did not conform to such hypothesis

because the animals did not cease their explorative behavior either in light or dark

conditions.

In this regard, exploratory behaviour could still be considered a form of compli-

cated and dynamic behavior as opposed to the more simple responses, either positive

or negative to a light source, due to the instability of the environment and the rapid

interactions between the animal and the world surrounding it. In the pond, typical

exploratory behaviour includes free movement of the animals upon reacting discrim-

inately to light intensity or color. Therefore, other behaviors such as looking around

while remaining in one location or resting against any object could not be considered

exploratory.

The critical conditions in exploratory behavior which could immediately shift to

escape and display avoidance behaviors were identified, i.e. when animals were being

exposed to strong light intensity, during the moult and post-moult or competitive in-

teractions among gender/size of animals while approaching the light source. During

exploration, males were more aggressive than females because they had larger chelae,

48

with larger individuals often intimidating and out-competing the smaller ones from the

shelters. This could also imply that crayfish should be harvested from ponds upon

reaching marketable size to reduce aggression and provide living space and food re-

sources for undersized animals. Understanding the way of catching, light traps could

be employed for possible solutions in developing environmental control measures.

Similar method of trapping with lights has been successfully replicated for other tra-

ditional fishing gear (e.g. “tempirai” or bamboo-stage trap) for collecting crustaceans

and fish from Barito River of Indonesia (Ahmadi and Rizani, 2012), and thus, could

most likely be adapted in the Southeast Asian region.

The ratio of catches to catch per unit of effort (CPUE) in all treatments could not be

standardized because the soaking period of the lights during operation was variable

and dependent on the type of light devices and variance in battery life. For example, a

0.45 W lamp SIL-1 (1.5 V) in the laboratory experiment would frequently turn off the

four lamps, although it was established that the use of LED lights provide a consid-

erable advantage over incandescent lights because of the higher energy efficiency of

LEDs, greater variability of available LED colors, and greater durability.

49

CHAPTER 4

SUMMARY AND CONCLUTIONS

The behavioral responses of P. clarkii to various DC electric stimuli were examined.

P. clarkii was sensitive to the polarity of the electric fields either faced or propelled

itself towards the anode. Through laboratory measurements, two threshold voltages

were determined i.e. threshold voltage I (0.04–0.10 V cm-1

), which induced parallel

orientation of the animal to the electric field and forward crawling toward the anode,

and threshold voltage II (0.12–0.16 V cm-1

), which induced flicking of the tail and

backward swimming toward the anode. The crayfish that displayed true electrotaxis

moved to the anode when stimulated within the space enclosed by the electrodes.

However, when the electrodes were elevated 5 cm or 10 cm off the bottom of the tank,

the crayfish moved to the anode, crawled through the gap beyond it and out of the

electric field. This movement beyond the anode cannot be explained by positive

electrotaxis, but it can be interpreted as repulsion from the cathode. The most effective

electric field intensity that induces anodal group response was 0.24–0.30 V cm-1

. At

higher level crayfish lay narcotized in the anode zone, but no crayfish were injury or

ever killed.

Phototactic behavior of P. clarkii at different developmental stages was evaluated

in indoor and outdoor tanks to determine their sensitivity thresholds to light, and

possible harvesting applications. Through laboratory measurements, the threshold

light intensity obtained was 46–659 lx, while the most effective light intensity that

induces highest positive photoresponse was 1,290 lx. Adult and juvenile crayfish were

found to be positively phototactic, while post-embryonic crayfish were negatively

phototactic. The positive phototaxis became more pronounce with increasing light

intensity in the laboratory, but the trapping unexpectedly showed no differences in

catch between lighted and dimmed traps due to the difference in light intensity might

not be large enough to cause a different catch.

50

For possible harvesting applications, the baited trap is most effective among the

four luring treatments. Trapping results indicate that when baited, lighted, and

non-baited traps are used, some crayfish prefer bait, some prefer light and the others

seek for a non-baited trap as a shelter. In addition, the use of light is more advanta-

geous because crayfish activity is much greater during the night than during the day.

Light may attract insect larvae and worms create a foraging opportunity for the cray-

fish. Lighted traps can also be used to harvest post-molt crayfish when they are not

attracted to food or bait after a molt. Light traps are not as effective as baited trap, but

are more environmentally friendly, since they reduce the waste of bait, and can use

rechargeable batteries.

In the laboratory experiment with no shelters, positive group responses were more

pronounced to lower light intensities than higher ones as well as green, while blue and

yellow lights were significantly different with the control. The trapping experiments

showed that trapping with incandescent lamps and LED lamps can be used to harvest

crayfish from ponds while their implications for environmental control measures were

established. The results also supported findings from other studies that P. clarkii had

true colour vision and able to alter independently their behaviour responses to different

colours. The method of trapping with lights could be replicated for other fishing gears,

habitats and target species.

Regarding eradication programs, electrofishing and trapping have been used to

remove large number of crayfish (e.g. Reeve, 2004; Ribbens and Graham, 2004), but

neither has been proven to be effective in total removal. Electrofishing is only effective

in shallow water, wet seeded rice fields or small ponds, and only catches a limited

portion of the crayfish population; therefore, it is not a viable method of control. Ex-

tensive baited-trapping may reduce crayfish density over time and slow down the

speed at which it spreads naturally, but it is also not an effective control method. It is

important to be able to assess how fast densities recover following program of removal.

Although the fyke-nets or baited traps are male-biased gear, the remaining females

may respond to recover population density by producing more eggs. To take a short cut

51

its reproduction, according to this study, egg-bearing females can be allured into a

lighted trap. Comparing to trapping, electrofishing represents a more realistic sex ratio

because can select females over males even they are less active during the breeding

seasons. Higher levels of trapping may succeed in eliminating a population, if it re-

duces the adult stock to levels where reproduction is insufficient to replace crayfish

that die or are removed. It is also possible that the more efficient trapping the greater

the recruitment, owing to a reduction in competition between trappable and untrap-

pable age classes (Reeve, 2004). No single method will be appropriate for all situations.

A combined strategy may be needed to overcome some of the limitations of individual

method (e.g. electrofishing with light, fyke-nets or baited trap with light, etc) and this

approach should be explored further.

52

REFERENCES

Ackefors, H., 1999. The positive effects of established crayfish introductions in Eu-

rope. In Gherardi, F., and D.M. Holdich (Eds.), Crayfish in Europe as alien species.

How to make the best of a bad situation? Balkema, Rotterdam, Brookfield, pp:

31-49.

Ahmadi, G. Kawamura, M. Vazquez Archdale and K. Anraku, 2008. True electrotaxis

and threshold voltages in the American crayfish Procambarus clarkii. J. Fish.

Aquat. Sci. 3(4): 228-239.

Ahmadi, Kawamura, G. and Archdale, M.V. 2008. Mechanism of photo taxis in

American crayfish Procambarus clarkii (Girard) following different methods of

trapping. Journal of Fisheries and Aquatic Science, 3(6): 340-352.

Ahmadi and Rizani, A. 2012. Catch efficiency of low-powered incandescent light and

LED light traps fishing in Barito River of Indonesia. Kasetsart University, Fish-

eries Research Bulletin, 36(3): 1-15.

Alonso, F., 2001. Efficiency of electrofishing as a sampling method for freshwater

crayfish populations in small creeks. Limnetica, 20(1): 59-72.

Balik, I., H. Cubuk, R. Ozkoka and R. Uysal, 2005. Some biological characteristics of

crayfish (Astacus leptodacctylus Eschscholtz, 1823) in Lake Egirdir. Turk. J. Zool.,

29(4): 295-300.

Bary, B. McK., 1956. The effect of electric fields on marine fishes. Mar. Res., 1: 1-32.

Bean, R.A. and J.V. Huner, 1979. An evaluation of selected crawfish traps and trap-

ping methods. Freshwater Crayfish, 4: 141-151.

Beaumont, W.R.C., A.A.L. Taylor, M.J. Lee and J.S. Welton, 2002. Guidelines for

electric fishing best practice. Environ. Agency Tech. Report W2-054/TR. WRc plc,

UK, pp: 179.

Bernardo, J.M., M. Ilheu and A.M. Costa, 1997. Distribution, population structure and

conservation of Austropotamobius pallipes in Portugal. Bull. Francais de la Peche

et de la Pisciculture, 347(4): 617-624.

53

Brown, D.J. and K. Bowler, 1977. A population study of the British freshwater

crayfish Austropotamobius pallipes (Lereboullet). Freshwater Crayfish, 3: 33-49.

Cain, C.D. and J.W.Jr. Avault, 1983. Evaluation of a boat-mounted electro-trawl as a

commercial harvesting system for crawfish. Aquac. Eng., 2: 135-152.

Capelli, G.M. and B.L. Munjal, 1982. Aggressive interactions and resource competi-

tion in relation to species displacement among crayfish of the genus Orconectes. J.

Crust. Biol. 2(4): 486-492.

Chaisemartin, C., 1967. Contribution a l’etude de l’economie calcique chez les

Astacidae. These Doct. Sci. Nat., Poitiers, France.

Chidester, F.E., 1912. The biology of the crayfish. Am. Nat. 46(545): 279-293.

Conover, W.J., 1980. Practical nonparametric statistics 2ed. Texas Tech. Univ. New

York, USA, pp: 493.

Culley, D.D., M.Z. Said and P.T. Culley, 1985. Procedures affecting the production

and processing of soft-shell crawfish. J. World Mar. Soc. 16: 183-192.

Culley, D.D. and Duobinis-Gray, L.F. 1989. Soft-shell crawfish production

technology. Journal of Shellfish Research, 8(1): 287-291.

Culley, D.D. and L.F. Duobinis-Gray, 1990. Culture of Louisiana soft crawfish.

Louisiana Sea Grant College Program. Center for wetland resources, Louisiana

State Univ., Baton Rouge, pp: 45.

Cummins, D. and Goldsmith, T.H. 1981. Cellular identification of the violet receptor

in the crayfish eye. Comparative Biochemistry and Physiology, 142: 199-202.

D’Abramo, L.R. and D.J. Niquette, 1991. Seine harvesting and feeding of formulated

feeds as a new management practices for fond culture of red swam crawfish

(Procambarus clarkii [Girard, 1852]) and white river crawfish (P. acutus acutus

[Girard, 1852]) cultured in earthen ponds. J. Shellfish Res., 2: 169-178.

Dorn, N.J., R. Urgelles and J.C. Trexler, 2005. Evaluating active and passive sampling

methods to quantify crayfish density in a freshwater wetland. J. N. Am. Benthol.

Soc. 24(2): 346-356,

54

Edwards, D.H, 1984. Crayfish extraretinal photoreception. I. Behavioural and

motoneuronal response to abdominal illumination. J. Exp. Biol. 109(1): 291-306.

Faller, M., I. Maguire and G. Klobucar, 2006. Annual activity of the noble crayfish

(Astacus asutacus) in the Orljava River (Croatia). BFPP/Bull. Fr. Peche Piscic.,

383: 23-40.

Fanjul-Moles, M.L. and Fuentes-Pardo, B. 1988. Spectral sensitivity in the course of

the ontogeny of the crayfish Procambarus clarckii. Comparative Biochemistry

and Physiology, 91A: 61-66.

Fanjul-Moles, M.L., M. Miranda-Anaya and B. Fuentes-Pardo. 1992. Effect of mon-

ochromatic light upon the ERG circadian rhythm during ontogeny in crayfish

Procambarus clarkii. Comparative Biochemistry and Physiology, 102A: 99-106.

Fanjul-Moles, M.L., Bosques-Tistler, T., Prieto-Sagredo, J., Castanon-Cervantes, O.

and Fernandez-Rivera-Ro, L. 1998. Effect of variation in photoperiod and light

intensity on oxygen consumption, lactate concentration and behavior in crayfish

Procambarus clarkii and Procambarus digueti. Comparative Biochemistry and

Physiology, 119A(1): 263-269.

Faulkner, G. and J.V. Huner, 1994. A polyethylene trawl system for harvesting crayfish,

Procambarus spp., in culture ponds. In Book of abstracts, annual meeting world

aquaculture society, New Orleans, Louisiana, US. World Aqua. Soc. Baton Rouge,

Louisiana, pp: 247.

Fernandez-de-Miguel, F. and H. Aréchiga, 1992. Sensory input mediating two oppo-

site behavioural responses to light in the crayfish Procambarus clarkii. J. Exp. Biol.

164(1): 153-169.

Fievet, E., L. Tito de Morais and A. Tito de Morais, 1996. Quantitative sampling of

freshwater shrimps: comparison of two electrofishing procedures in Caribbean

stream. Arch. Hydrobiol. 138(2): 273-287.

Gallagher, M.B., J.T.A. Dick and R.W. Elwood, 2005. Riverine habitat requirements

of the white-clawed crayfish, Austropotamobius pallipes. Biol. Envi.: Proceedings

of the Royal Irish Academy. 106B(1): 1-8.

55

Garvey, J.E., R.A. Stein and H.M. Thomas, 1994. Assessing how fish predation and

interspecific prey competition influence a crayfish assemblage. Ecology, 75(2):

532-547.

Gaude, A.P., 1986. Ecology and production of Louisiana red swamp crawfish

(Procambarus clarkii) in southern Spain. Freshwater Crayfish. 7: 171-177.

Gherardi, F., S. Barbaresi and G. Salvi, 2000. Spatial and temporal patterns in the

movement of Procambarus clarkii, an invasive crayfish. Aqua. Sci. 62(2):

179-193.

Goyert, J.C. and J.W.Jr. Avault, 1978. Effects of stocking density and substrate on

growth and survival of crayfish (Procambarus clarkii) grown in a recirculating

system. Proceeding of the World Mar. Soc., 9: 731-735.

Habsburgo Lorena, A.S., 1983. Some observations on crawfish farming in Spain.

Freshwater Crayfish, 6: 131-132.

Hafner, G.S. and Tokarski, T.R. 1998. Morphogenesis and pattern formation in the

retina of the crayfish Procambarus clarkii. Cell and Tissue Research, 293:

535-550.

Hariyama, T., Ozaki, K., Tokunaga, F.and Tsukahara, Y. 1993. Primary structure of

crayfish visual pigment deduced from cDNA. Fed Eur Biochemical Society,

315(3): 287-292.

Hein C. L., M.J. Vander Zanden and J.J. Magnuson, 2007. Intensive trapping and in-

creased fish predation cause massive population decline of an invasive crayfish.

Freshwater Biol., 52(6): 1134-1146.

Henttonen, P. and J.V. Huner, 1999. The introduction of alien species in Europe: a

historical introduction. In: Crayfish in Europe as alien species, Gherardi, F. and

D.M. Holdich (Eds.). A. A. Balkema, Rotterdam. Crust. Issues, 11: 13-22.

Higman, J.B., 1956. The behaviour of pink grooved shrimp Penaeus duorarum

Burkenroad, in a direct current electrical field. Tech. Ser. No. 16. Mar. Lab., Univ.

Miami, pp: 24.

56

Hill, A.M. and D.M. Lodge, 1994. Diel changes in resource demand: competition and

predation in species replacement among crayfishes. Ecology, 75(7): 2118-2156.

Hobbs, H.H.Jr., 1988. Crayfish distribution, adaptive radiation and evolution. In:

Freshwater Crayfish: Biology, Management and Exploitation (Eds. Holdich, D.M.

and R.S. Lowery), pp: 52-82, Croom Helm, London.

Holdich, D.M. and J.C.J. Domaniewski, 1999. Studies on a mixed population of the

crayfish Austropotamobius pallipes and Pacifastacus leniusculus in England.


Holdich, D.M., 2002 (Ed.). Biology of freshwater crayfish. Blackwell Science, Oxford,

pp: 702.

Huner J.V. and J.W.Jr. Avault, 1977. Investigation of methods to shorten the intermold

period in a crawfish, Proceedings World Mar. Soc. 8: 883-893.

Huner, J.V. and R.P. Romaire, 1979. Size a maturity as a means of comparing popu-

lations of Procambarus clarkii (Girard) (Crustacea: Decapoda) from different

habitats. Paper from the Int. Symp. on Freshwater Crayfish, 1: 53-64.

Huner, J.V. and R.P. Romaire, 1990. Crawfish culture in the southeastern USA. World

Aquaculture 21: 58-65.

Huner, J.V. 1990. Biology, fisheries, and cultivation of freshwater crawfishes in the

US. Rev. Aquatic Sci. 2: 229-254.

Huner, J.V. and J.E. Barr, 1991. Red swamp crawfish: biology and exploitation (3rd

Ed.). Louisiana Sea Grant Coll. Prog. Louisiana State Univ. Baton Rouge, pp: 128.

Huner, J.V., 1994. Cultivation of freshwater crayfish in North America. Section 1.

Freshwater crayfish culture. In Huner, J.V. (Ed.), Freshwater crayfish aquaculture

in North America, Europe and Australia. Families Astacidae, Cambaridae, and

Parastacidae. Haworth press, Binghamton, New York, pp: 5-89, 137-156.

Huner, J.V. and O.V. Lindqvist, 1995. Physiological adaptations of freshwater cray-

fishes that permit successful aquacultural enterprises. American Zoologist, 35(1):

12-19.

57

Huner, J.V., 1998a. The Louisiana crawfish story. Louisiana Wildlife Federation

Magazine, 26(2): 32-35.

Huner, J.V., 1998b. Evaluation of trap density and type for harvesting crawfish

Procambarus spp from small ponds. J. World Aqua. Soc., 29(1): 104-107.

Hyatt, M.W., 2004. Investigation of crayfish control technology. Final Report. Coop-

erative Agreement No. 1448-20181-02-J850. Arizona Game and Fish Department,

Phoenix, pp: 93.

Kawai, T., K. Nakata and Y. Kobayashi, 2002. A study of the taxonomic status and

introduction of two Pacifastacus crayfish species from North America to Japan. J.

Nat. Hist. Aomori, 7: 59-71. (in Japanese with English abstract).

Kawai, N., R. Kono and S. Sugimoto, 2004. Avoidance learning in the crayfish

(Procambarus clarkii) depends on the predatory imminence of the unconditioned

stimulus: a behavior systems approach to learning in invertebrates. Behavioural

Brain Res. 150: 229-237.

Kessler, D.W., 1965. Electrical threshold responses of pink shrimp Penaeus duorarum

Burkenroad. Bull. Mar. Sci., 15(4): 885-895.

Klima, E.F., 1968. Shrimp behaviour studies underlying the development of the

electric shrimp trawl system. Fish. Ind. Res., 4(5): 165-181.

Klima, E.F., 1972. Voltage and pulse rates for inducing electrotaxis in twelve coastal

pelagic and bottom fishes. J. Fish. Res. Bd. Can., 29(11): 1605-1614.

Ko, K.S., S.H. Kim and G.D. Yoon, 1972. Electrical fishing method of Penaeus

japonicus Bate. Bull. Korean Fish. Soc., 5(4): 115-120.

Koeller, P. and G. Crowell, 1998. Electrotaxis in American lobster Homarus

americanus, and its potential use in sampling early benthic-phase animals. Fish.

Bull., 96(3): 628-632.

Kong, K.L. and Goldsmith, T.H. 1977. Photosensitivity of retinular cells in white-eyed

crayfish (Procambarus clarkii). Comparative Biochemistry and Physiology, 122:

273-288.

58

Kozak, P. and T. Polizar, 2003. Practical elimination of signal crayfish, Pasifastacus

leniusculus (Dana) from a pond. In Holdich D.M and P.J. Sibley (Eds.) 2003.

Management and conservation of crayfish. Proceedings of a conference held on 7th

November 2002. Environment Agency. Bristol. pp: 217.

Kozak, P., J. Martín and J. Escudero, 2007. Selective behaviour of Procambarus

clarkii in a light gradient. In Book of abstracts, 15th International conference on

aquatic invasive species. Nijmegen, the Netherlands, pp: 66.

Kurohagi, T., 1991. Present situation of Lake Shiraribetsu., pp: 35-39. In Nagano, A.

(Ed.) Rise. Gimming, Sapporo, Japan. (in Japenese).

Lamarque, P., 1990. Electrophysiology of fish in electric fields. In: Fishing with

electricity: Applications in freshwater fisheries management, Cowx, I.G. and P.

Lamarque (Eds.). Fishing News Books, Oxford, pp: 4-33.

Lamontage, S. and J.B. Rasmussen, 1993. Estimating crayfish density in lakes using

quadrats: maximizing precision and efficiency. Can.J.Fish.Aqua.Sci. 50: 623-626.

Maitland, P.S., C. Sinclair and C.R. Doughty, 2001. The status of freshwater crayfish

in Scotland in the year 2000. Glasgow Naturalist, 23(6): 26-32.

Maronek, T.G., 1994. Status of the bait industry in the north central region of the

United States. M.S. Thesis. Univ. Wisconsin-Stevens Point, Wisconsin, pp: 250.

McClain, W.R., J.L. Avery and R.P. Romaire, 1998. Crawfish production: production

systems and forages. SRAC Publication No. 241, pp: 4.

Miyake, S., 1982. Japanese crustacean decapods and stomatopods in color I: 1-264.

(Hoikusya, Osaka, Japan). (in Japanese).

Nakamura, K., 1980. Quantitative analysis on the feeding patterns of the crayfish

relating to the molting cycle. Mem. Fac. Fish. Kagoshima Univ. 29: 225-238. (in

Japanese, with English abstract).

Nakata, K. and S. Goshima, 2003. Competition for shelter of preferred sizes between

the native crayfish species Cambaroides japonicus and the alien crayfish species

Pacifastacus leniusculus in Japan in relation to prior residence, sex difference, and

body size. J. Crust. Biol. 23(4): 897-907.

59

Nakatani, I. and N. Yokohama, 2003. The signal crayfish Pacifastacus leniusculus

species in Lake Onogawa on the National Park Bandai Asahi. Cancer 12: 27-28.

[In Japanese].

Nakata, K., T. Hamano, T. Kawai, M. Hirata, the Otofuke River Groundwork Group,

Y. Takakura, H. Kagami and K. Tsutsumi, 2001. Distributions of crayfish in the

Tokachi region of Hokkaido, Japan, with notes on temporal changes in density.

Rep. Obihiro centen. City Mus., 19: 79-88. (in Japanese, with English abstract)

Nakata, K., T. Hamano, K. Hayashi, T. Kawai, 2002. Lethal limits of high temperature

for two crayfishes, the native species Cambaroides japonicus and the alien species

Pacifastacus leniusculus in Japan. Fish. Sci. 68: 763-767.

Nakata, K., A. Tanaka and S. Goshima, 2004. Reproduction of the alien crayfish

species Pacifastacus leniusculus in Lake Shikaribetsu, Hokkaido, Japan. J. Crust.

Biol. 24: 496-501.

Nakata, K., K. Tsutsumi, T. Kawai and S. Goshima, 2006. Coexistence of two North

American, Pacifastacus leniusculus (Dana, 1852) and Procambarus clarkii

(Girard, 1852) in Japan. Crustaceana, 78(11): 1389-1394.

Newland, P.L. and D.M. Neil, 1990. The tail flip of the Norway lobster, Nephrops

norvegicus II. Dynamic righting reactions induced by body tilt. J. Comp. Physiol.

A: Neuroethology, sensory, neural, and behavioral physiology, 166(4): 529-536.

Nosaki, H. 1969. Electrophysiological study of color encoding in the compound eye of

crayfish, Procambarus clarkii. Zeitschrift für vergleichende Physiologie, 64:

318-323.

Nystrom, P., P. Stenroth, N. Holmqvist, O. Berglund, P. Larsson and W. Graneli, 2006.

Crayfish in lakes and streams: individual and population responses to predation,

productivity and substratum availability. Freshwater Biol. 51: 2096-2113.

Olouch, A.O. 1990. Breeding biology of the Louisiana red swamp crayfish

Procambarus clarkii (Girard) in Lake Naivasha, Kenya. Hydrobiologia,

208(1-2): 85-92.

60

Page, T. and J.L. Larimer, 1972. Entrainment of the circadian locomotor activity

rhythm in crayfish. The role of the eyes and caudal photoreceptor. J. Comp.

Physiol. 78(2): 107-120.

Pease, N.L. and W.R. Seidel, 1967. Development of the electro-shrimp trawl system.

Commercial. Fish. Rev., 29(8-9): 58-63.

Penczak, T. and G. Rodriguez, 1990. The use of electrofishing to estimate population

densities of freshwater shrimps (Decapoda, Natantia) in a small tropical river,

Venezuela. Archiv. Hydrobiol., 18 (4): 501-509.

Phillips, B.F. and A.B. Scolaro, 1980. An electrofishing apparatus for sampling sub-

litoral benthic marine habitats. J. Exp. Mar. Biol. Ecol., 47: 69-75.

Polet, H., F. Delanghe and R. Verschoore, 2005. On electrical fishing for brown

shrimp (Crangon crangon): I. Laboratory Experiments. Fish. Res. 72 (1): 1-12.

Rabeni, C.F., K.J. Collier, S.M. Parkyn and B.J. Hicks, 1997. Evaluating techniques

for sampling stream crayfish (Paranephrops planifrons). New Zealand J. Mar.

Freshw. Res. 31: 693-700.

Reeve, I.D., 2004. The removal of the North American signal crayfish (Pacifastacus

leniusculus) from the River Clyde. Scottish Natural Heritage Commissioned Re-

port No. 020 (ROAME No. F00LI12), pp: 55.

Ribbens, J.C.H. and J.L. Graham, 2004. Strategy for the containment and possible

eradication of American crayfish (Pacifastacus leniusculus) in the River Dee

catchment and Skyre Burn catchment, Dumfries and Galloway. Scottish Natural

Heritage Commissioned Report No. 014 (ROAME No. F02LK05), pp: 51.

Richards, C., Gunderson, J., Tucker, P.and McDonald, M. 1995. Crayfish and baitfish

culture in wild rice paddies. Natural Resources Research Institute. Technical

Report No. NRRI/TR-95/39. University of Minnesota, Duluth, USA. 35 pp.

Romaire, R.P., 1995. Harvesting methods and strategies used in commercial

procambarid crawfish aquaculture. J. Shellfish Res., 14: 545-551.

Saito, K. and S. Hiruta, 1995. Procambarus clarkii living in Hokkaido. Asahikawa

City Museum Kenkyu Houkoku, 1: 9-12 (in Japanese).

61

Salia, S.B. and C.E. Williams, 1972. An electric trawl system for lobsters. Mar. Tech.

Soc. J., 6: 25-31.

Seidel, W.R. and J.W. Watson, 1978. A trawl design: employing electricity to

selectively capture shrimp. Mar. Fish. Rev., 40(9): 21-23.

Shigueno, K., 1975. Shrimp culture in Japan. Association for International Technical

Promotion, Tokyo, pp: 72-76.

Sinclair, C. and J. Ribbens, 1999. Survey of American signal crayfish, Pacifastacus

leniusculus, distribution in the Kirkcudbrightshire Dee, Dumfries and Galloway,

and assessment of the use of electrofishing as an eradication technique for crayfish

populations. Scottish Natural Heritage.

Snyder D.E., 2003. Electrofishing and its harmful effects on fish. Inform. Tech. Rep.

USGS/BRD/ITR-2003-0002. US Gov. Print. Off., Denver, pp: 149.

Somers, K.M. and Stechey, D.M., 1986. Variable trapability of crayfish associated

with bait type, water temperature and lunar phase. Am. Mid. Nat. 116(1): 36-44.

Somers, K.M. and R.H. Green, 1993. Seasonal patterns in trap catches of the crayfish

Cambarus bartoni and Orconectes virilis in six south-central Ontario lakes. Can. J.

Zool. 71(6): 1136-1145.

Soderhall, K., E. Svensson and T. Unestem, 1977. An inexpensive and effective

method for elimination of the crayfish plague: barriers and biological control.


Stebbing, P.D., G.J. Watson, M.G. Bentley, D. Fraser, R. Jennings, S.P. Rushton and

P.J. Sibley, 2004. Evaluation of the capacity of pheromones for control of invasive

non-native crayfish. English Nat. Res. Rep. No. 578, Peterborough, UK, pp: 36.

Stewart, P.A.M., 1974. An investigation into the effects of electric fields on Nephrops

norvegicus. J. Cons. Int. Explor. Mer. 35(3): 249-257.

Stewart, P.A.M., 1975. Comparative fishing for Nephrops norvegicus Linnaeus using a

beam trawl fitted with electric ticklers. Scotland Dept. Agric. Fish. Mar. Res., 1:

1-10.

62

Sukô, T., 1953. Studies on the development of the crayfish. I. The development of

secondary sex characters in appendages. Sci. Rep. Saitama. Univ. 1: 77-96.

Taugbol, T., S.B. Waervagen, A.N. Lineokken and J. Skurdal, 1997. Post-molt

exoskeleton mineralization in adult noble crayfish, Astacus astacus, in three lakes

with different calcium levels. Freshwater Crayfish, 11: 219-226.

Travis, D.F., 1960. The deposition of skeletal structures in the crustacea. I. The

histology of the gastrolith skeletal tissue complex and the gastrolith in the crayfish,

Orconectes (Cambarus) Virilis Hagen-Decapoda. Biol. Bull., 118(1): 137-149.

Unestam, T., C.G. Nestell and S. Abrahamsson, 1972. An electrical barrier for

preventing migration of freshwater crayfish in running water. A method to stop the

spread of the crayfish plague. Rep. Inst. Freshw. Res., Drottningholm, 52:

199-203.

Usio, N., M. Konishi and S. Nakano, 2001. Species displacement between an

introduced and a ‘vulnerable’ crayfish: the role of aggressive interactions and

shelter competition. Biol. Invasions, 3: 179-185.

Usio N., K. Nakata, T. Kawai and S. Kitano, 2007. Distribution and control status of

the invasive signal crayfish (Pacifastacus leniusculus) in Japan. Jap. J. Limnol.

68: 471-482 (in Japanese with English abstract)

Wathne, F., 1967. Shrimp reaction to electrical stimulus. In: Fishing with electricity:

Its application to biology and management, Vibert, R. (Ed.). Fishing News Books,

London, pp: 566-570.

Westman, K., O. Sumari and M. Pursiainen, 1978. Electric fishing in sampling

crayfish. Freshwater Crayfish, 4: 251-256.

Westman, K., 2002. Alien crayfish in Europe: negative and positive impact and

interactions with native crayfish. In: Invasive Aquatic Species of Europe (Eds.

Leppakoski, E., S. Gollasch, S. Olenin), pp: 76-95. Kluwer Acad. Publ. Netherland.

Witzig, J.F., J.V. Huner and J.W.Jr. Avault, 1983. Crawfish (Procambarus clarkii)

growth and dispersal in a small south Louisiana pond planted with rice (Oryza

sativa). Freshwater Crayfish, 5: 331-334.

in American Crayfish Electrotaxis and Phototaxis The ...eprints.ulm.ac.id/5942/1/Buku...

Documents

Transcript of in American Crayfish Electrotaxis and Phototaxis The ...eprints.ulm.ac.id/5942/1/Buku...