17

Chapter 3

MATERIALS AND METHODS

Study area-River Kali

Karnataka state is one of the maritime state located on the central west coast of India

which comprises three coastal districts, namely Uttara Kannada, Udupi and Dakshina

Kannada. Uttara Kannada district has five coastal taluka namely Karwar, Ankola, Kumta,

Honnavar and Bhatkal. Karwar being located on the northern part of the Uttara Kannada

district, where this river flow through the Sahyadri Ghat region and ultimately joins the

Arabian Sea in Karwar.

The Uttara Kannada maritime district has blessed with four major riverine systems

which drain into the Arabian Sea, among which the river Kali located on the northern most

sector of the district and is followed by the Gangavali, Aghanashini and Sharavati in the

south (Figure 1). All these rivers form productive estuarine complex which harbour highly

rich resources of fin fishes and shell fishes reflecting the exceptionally high inshore fishery

all along this coast. Further, the trailing creeks, backwaters and mangrove areas are proved to

be ideal culture sites where extensive culture of prawns has been practiced. In addition, the

rich clam and oyster resources of these estuaries support a number of lime industries. Many

families are solely dependent on this cottage industry for their livelihood.

The River Kali originated in the Kusavali village in Supa taluka and after meandering

about 185 km in the Sahyadri plateau and lastly joins the Arabian Sea at Karwar (14o50’21”

N and 74o10’05”E). River Kali exhibits different type of biotopes such as estuary,

backwater, fresh water and mangrove, grassland etc. The environmental parameters of

aquatic biotope fluctuate periodically dependable on the three conspicuous seasons, pre-

monsoon (February-May), southwest monsoon (June-September) and post-monsoon

(October-January). The pre monsoon season is identified by high temperature and salinity,

the south- west monsoon season is characterized by heavy rainfall, and greater riverine

discharge and land run off. The post-monsoon season is known for stable environmental

conditions and a high biological productivity rate.

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Topographically the area can be classified as the coastal belt, extends northerly as a

succession of estuarine plains connected by narrow coastal strips. The coastal taluka is

characterized with low and raising hillocks.

The River Kali flows at the beginning in a southeasterly direction then easterly, south,

south easterly and southwest for a length of more than 50km and takes sudden westward turn

and flows up to the confluence with Arabian Sea (Fig.1). The west flowing rivers before

confluence with Arabian Sea are used for navigation and serve as transport ways for

hinterland. The drainage pattern is dendritic to sub-dendritic in nature. The drainage

density ranges from 1 to 3km/Km2. The west flowing rivers are controlled by structures of

the geological functions. River Kali and its tributaries change their course very often.

The Kali Hydroelectric project built across river Kali at Supa generates 315 MW

power and the hydroelectric project built across the same River at Kadra dam generates 150

MW. The total impounding of surface water in Kali River is 4461 MCM for a normal rainfall

year.

Among the four estuarine systems of Uttara Kannada coast, river Kali is the major

one. This partially mixed estuary, spreads approximately about 25 kms in axis until the edge

of the elevated plateau of Sahyadri (14o 54’ 25” N and 74

o 19’ 30” E) and drains into the

Karwar Bay (14o 50’ 21” N and 74

o 10’ 05” E) on the central west coast of India (Fig. 1).

The total water spread area of the river is 4850 sq.km. The maximum width is found at the

mouth of Kadwad backwaters measuring nearly 2 km with an island at the center. The total

low lying area in the lower reaches of the river is about 1217 acres which includes the

villages of Kanasgeri, Hotegali, Hankon, Sunkeri and Kadawad areas. Either bank are

moderately populated being free from pollution as there has been no major industrial set up.

The deepest part of the estuary is found be at about 18 km. upstream near Halga, where depth

on an average is 15 metres. This is the area of maximum erosion due to the estuarine

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meandering. Depth near the mouth of the estuary depends on the seaward elevation of the

sand bar and its consequent temporal movements along with the changes in tide.

The backwater system, owing to the geography of the area and availability of low

lying area is moderately developed. On the north-west sector of estuarine mouth a 10 km

long Mavinahole creek extends northwards and the Kodibag creek extends to the south to

about 1 km. The Sunkeri and Kadwad backwater system which covers a vast area is

variously used for fishing, transport of cargo and culture purposes. Around 4km away from

the estuary, there is one more backwater system exists on the northern bank of River Kali is

the Knasgeri backwaters considerably good productivity zone. All these backwaters are

thickly populated with green, lush and good growth of mangrove flora which has escalated

the productivity and biotic resources of this Kali River

As elsewhere found in the riverine system of west coast of India, the environmental

characteristics of the river Kali also fluctuate periodically depending on the three conspicuous

seasons (Harakantra, 1975), the pre monsoon (February-May), southwest monsoon (June-

September) and post monsoon (October-January) respectively. The overall annual rainfall in

this area is about 3000mm and maximum precipitation is observed during the southwest

monsoon season followed by the post monsoon which is very negligible. The pre monsoon

season is identified by high regime of temperature and salinity while the south west monsoon

season is characterized by heavy precipitation (rainfall), greater riverine discharge resulting

in consequent dilution of the inshore water. The post monsoon season is known for the stable

environmental conditions establishing a high biological productivity regime.

River Kali is highly productive with a high density of fin & shellfish species and other

biotic communities. An understanding of the seasonal pattern of plankton ecology in the

river is not only important to fishery management but also theoretical interest. Hence, the

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River is chosen to investigate the physico-chemical parameters, biotic ecology and the

seasonal changes in their abundance and distribution with respect space and time with special

reference to the mangrove ecosystem.

B) Study Sites

Totally five study stations were selected and fixed in the mangrove ecosystem of Kali

estuary, Karwar on West coast of India. The geographical position of each study station is

given in the Table 1 and the location of study stations are shown in the Plate No.1 and Figure

1.

Table 1. Geographical positions of the Study stations

Station

Number

Station Geographical position Distance from

the River

mouth

1 Mavinahole creek

14o 50’ 39” N and 74o 07’ 44” E 1.05 km

2 Kanasgeri 14o 51’ 28” N and 74o 09’ 08” E 3.25 km

3 Sunkeri 14o 50’ 15” N and 74o 10’ 14” E 5.75 km

4 Kadwad 14o 50’ 58” N and 74o 10’ 51” E 9.15 km

5 Kinnar 14o 51’ 49” N and 74o 13’ 25” E 12.50 km

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Station 1: This study station is located in the Mavinahole creek which is situated at

northern part of the Kali estuary, where the hydrographical parameters are highly influenced

by the influx of river water and inshore waters. The depth of light attenuation varies

considerably with day-length period. The productivity of this area is very good with vast

assemblages of different mangrove floral species (Plate 2).

Station 2: Is fixed in the backwaters of Kanasgeri, which is about 3.25 km away from the

estuary point located on the northern bank of River Kali and has a vast and luxuriant growth

of mangrove floral stretch. This is one of the fishing areas in and around the Kali estuary and

fishing activities can be seen here throughout the year (Plate 2).

Station 3: This study station is also located in the mangrove habitat Sunkeri which is about

5.75 km from the estuary point and located at the southern bank of the river is covered with

rich mangrove floral stretch with maximum mangrove species. This area also supports good

fishery of fin-fishes like mullets (Mugil cephalus) and pearl spot (Etroplus suratensis),

Scatophagus sp., and shellfishes like prawn & crab species etc. Productivity of this study

area is considerably very high (Plate 3).

Station 4: This study station is around 9 km from the Kali estuary and is located in the

Kadwad area. This study point located in the mangrove habitat of the river and this area is

also known for good fishery throughout the year (Plate 3). Thick and luxuriant growth of

mangrove flora is seen in this area and comparatively good numbers of mangrove species

have been recorded from this area.

Station 5: This study station is located in the Kinnar which is around 12.5 km from the

estuarine point and is mostly fresh water biotope with more number of freshwater fin fish

species (Plate 3). Sand mining and other related works being carried out here throughout the

year and water column is more turbid compared to other study areas.

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C) Methods of Sampling and Analysis

Water, sediment and biotic (zooplankton, macrobenthos, mollusks, arthropods and fin

fishes) samples were collected from the five fixed stations for the period of thirteen

months from January 2008 to January 2009 at regular monthly interval. Samplings and

analysis of samples were made as per the standard procedure (APHA, 2000).

C.1. Environmental Parameters

To study the impact of the environmental parameters on faunal (biotic) population in space

and time, the following environmental parameters were selected. They are water

temperature, salinity, dissolved oxygen, hydrogen ion concentration, suspended matter,

and nutrients like Phosphate-P, Nitrate-N, Nitrite-N and Silicate-Si respectively. Besides

this, the sedimentological parameters were also studied and are discussed in the following

paragraphs.

a) Hydrography:

The water samples were collected with the help of Casella bottle to a depth usually not

deeper than one metre from the surface layer of water. The GPS instrument was used to

locate the sampling site every time. Samples were collected from the same stations at the

same time of the day, each month during the entire period of study. The water samples

were then transferred to a separate, cleaned polythene bottles for estimation of different

physico-chemical parameters. Following hydrographic parameters were studied (Table 2)

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Table 2. List of hydrographic parameters

Parameters Units used

Temperature o C (degree celsius)

Salinity ‰ (parts per thousand)

Dissolved oxygen ml/l (mililitre per litre)

pH

(Hydrogen ion concentration)

-

Suspended matter g/l (gram per litre)

Phosphate-P µg at/l (microgram atom per litre)

Nitrate-N µg at/l (microgram atom per litre)

Nitrite-N µg at/l (microgram atom per litre)

Silicate-Si µg at/l (microgram atom per litre)

Water temperature:

The water temperature was recorded using the thermometer, which was sent to the desired

depth along with the Casella bottle.

Salinity:

Salinity of water sample was determined by Mohr Knudsen method as described by

Strickland and Parsons (1975) and the values are expressed in parts per thousand (‰).

Refractrometer was also made use in the field to determine the salinity content of the water

(Plate No. 2).

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Dissolved Oxygen:

Dissolved oxygen content in the water sample was estimated by following the

Winkler’s method as per the procedure described by Strickland and Parsons (1975) and

values expressed in ml/litre.

Hydrogen ion concentration:

The pH of the water sample was estimated in the site itself by using the portable pH

meter (model LI-120) on the board and recorded the readings.

Suspended matter:

Amount of suspended matter in the study site water was estimated by filtering one

litre of water sample through pre weighed Whatman G/F filter paper which was dried to

constant weight at 90-105oC and reweighed, the difference between the two values gives the

weight of the suspended matter. The values are expressed in gm/litre (Rama Rao et al.,

1985).

Nutrients:

Collected water samples were used for estimation of different nutrient elements such

as phosphate-phosphorus, nitrate-nitrogen, nitrite-nitrogen and silicate-silicon as per the

standard methods described by Strickland and Parsons (1975), APHA (2000). The values are

expressed in µg at per l-1

.

Pearson’s correlation co-efficient matrix (r) for hydrographic parameters of each

study site was calculated by using the formula as given hereunder:

Σ х y – 1/n Σх x Σy

(r)= ____________________________

√Σх2

– 1/n (Σх)2√ Σy

2-1/n (Σy)

2

Where ‘х’ and ’y’ are any two parameters

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b) Sedimentology:

Regular monthly collections of bottom water, sediment and benthos were made for a

period thirteen months from January 2008 and January 2009 at five different study sites using

the motorized outrigger canoe. The sediment samples were collected with the help of a

Petersen grab having mouth biting an area of 2651.7cm2 and depth of 15cm. A plastic core

or quadrate was used to take sample from the central part of the grab sample and was

immediately brought to the laboratory for further analyses. Subsequently these samples were

analyzed to study the benthic population as well as sediment texture in the mangrove

ecosystem of Kali estuary for period of thirteen months. The sedimentological parameters

analyzed and the units of each parameter are given in the Table 3.

Table 3. List of sedimentological parameters

Parameters Units used

Temperature o C (degree celsius)

pH (Hydrogen ion concentration -

Moisture % (percentile)

Interstitial water % (percentile)

Organic carbon % (percentile)

Sand/Silt/Clay % (percentile)

Sediment temperature:

After collection of the sediment samples, immediately the scientific thermometer was

inserted into the sediment samples and sediment temperature was recorded and expressed as

degree Celsius (o C).

pH: The sediment pH values were obtained by using the sediment pH probe.

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Moisture content:

Moisture content of the sediment was calculated by taking a known amount (>20gms)

of sediment in a pre-weighed Petri dish & dried in oven at constant temperature of 110oC

until all the moisture is evaporated. The difference between the wet weight and dry weights

of the sediment gives the moisture content of the sediment and is represented as percentile

(%).

The moisture content (%) was calculated as follows:

Moisture (%) = Wet weight - Dry weight x 100

Wet weight

Interstitial water:

The interstitial water content was determined by drying the sediment in a constant

temperature (110o C). The values were represented as percentile of the weight of the sediment

used for analyses.

Organic Carbon:

This parameter was determined by following the method as described by El Wakeel &

Riley (1956). This is to evaluate the organic carbon content in the sediment and the results

were represented as percentile (%) respectively.

Sediment texture:

Sediment grain size analysis was carried out with the help of sieves. Silt and clay

fractions were determined by pipette analysis as described by Holme & McIntyre (1971).

Later, the results were plotted on triangular diagrams (Eltringham, 1971; Holme & McIntyre

1971;Parsonset al., 1977) and the sediment texture was determined.

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The depth could not be considered as an additional bearing during the relocation of

the stations as it varied around the year owing to land run off and other natural processes.

Hence, the standard deviation of depth is calculated the values are given in Table 1. The

standard deviation is determined as follows,

Standard deviation = √ Σ (m – M)2

n

Where, m = depth in different months

M = mean depth

n = number of sampling

C.2. Biotic Parameters

a) Zooplankton:

The zooplankton samples were collected from the surficial stratum from five stations

located at mangrove ecosystem of Kali estuary (Fig.1), during the present study period. The

zooplankton were collected using a modified plankton net (mouth area 0.35m2 and mesh

width 0.28 mm) fitted with calibrated flow meter. The net was towed for about 5 minutes

and the samples were fixed in 5% buffered formaldehyde solution. The density was

determined by numerical method using Sedgewick’s counting chamber under the microscope.

Various planktonic groups and their species were enumerated by examining 5-10% of the sub

sample and the number of organisms computed per m3

of water (Wickstead, 1965: NIO

Manual,2000)..

b) Macrobenthos :

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The undisturbed sediment collected with the help of Petersen grab was sampled first

for benthos. A plastic corer was used for further sampling. The 10cm deep core samples

were treated with 1:500 Rose-bengal formaldehyde solutions and were transported to the

laboratory in polythene bags. The sediment was sieved between 500 and 62 microns. The

residue obtained on the sieve of 500 microns was preserved in rose Bengal solution for

qualitative & quantitative of macro benthos. Later, the samples were studied under

microscope to identify the benthic taxa (Holme & McIntyre 1971; Parsons et al., 1977). A

total of 65 samples for macro benthos were taken for analysis with equal number of samples

from each of the five study sites.

c) Shell fishes:

i) Molluscs:

Molluscs were collected by hand picking. The clams were collected from

1 x 1 m quadrate area during low tide period. The oysters were collected from chisel and

sharp knife from the 1 x 1 m quadrate area of small rocks during low tide period otherwise

these rocks are submerged in the water during the high tide time (CMFRI Bulletin, 2000).

ii) Arthropods:

The distribution and abundance of shellfishes (crustaceans) were recorded by

collecting them with the help of drag net (3m x 1m size) having mesh size of 0.5cm. The net

was dragged for the period of 7 to 10 minutes duration covering the area of about 10m2.

Collected specimens were preserved in 5% formalin solution for further analysis. Average of

three hauls were taken in the present study. Identification of crustaceans was done using the

standard identification manuals (CMFRI Bulletin, 2000).

d) Fin fishes:

The fin fishes were collected from the respective study stations using the drag net and

cast net. The length of the drag net was 14.3’ and width 3.5’and the sinkers having 1cm in

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length were rigged at a regular interval of the foot selvage of the drag net. At both ends, two

bamboo poles were fixed to ease the dragging. Throughout the length of the net, uniform

mesh size (5mm) was retained. This net was dragged for about 10 minutes for two times in

each sampling. Cast net used was measuring about 2.8m in height with pockets in the

peripheral line with uniform mesh size of about 3mm and was operated two times for every

sampling. After collection of fin fishes from each net, later they were preserved in the 5%

formalin for further studies like taxonomy and morphometries in the laboratory. Fishes were

caught and identified up to species level but some have identified up to genus level (Day’s

volume, 1962 and FAO Catalogue, 2000). The total density of fin fishes were calculated and

represented for an area of one square metre (No/m2).

e) Woodborers:

The woodborer animals were collected from the mangrove area during the low tide at

regular monthly intervals. Collections were made manually by using the tongs, forceps,

pointer or bodkin to pierce the wood and lift them from the wood found in the mangrove area.

While collecting these animals from their den, care was taken not to cut or damage their body

and without disturbing other fauna from the area and their density was represented for one

square metre (No/m2) (Santhakumaran, 1994 & 96).

f) Avian fauna:

The bird community on the exposed mangrove mud flat area was scanned at monthly

intervals from an indigenous dugout canoe with an outboard motor engine moving at uniform

speed of 10km per hour for the period from January 2008 to January 2009.

Foot trails were conducted into the dense mangroves not accessible by boat and the

birds therein were listed. The birds sighted were indentified using relevant field guides

(Woodcock,1980; Ali and Ripley, 1983; Sonobe and Usui, 1993; Grewal, 1995’

Ali,1996;Grimett et al., 1998). A combination of Total Count Method and LinearTransact

count method standardized o meet the requirement of the site were employed An binocular

and 15-45x60 spotting scope was used for the this purpose.

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g) Mangroves:

Referring to the Mangrove manual (NIO, Bulletin), text books and other periodicals, the

field study was carried in each study site and the checklist of mangrove species were

prepared for the period from January 2008 to January 2009.

Statistics:

The biotic entities reflect the ecological and environmental status and were calculated

in terms of number of individuals or specimens (N), number of species (S), total abundance

(A), Margalef species richness (d), Pielou’s evenness (J’), Shannon index (H’) at each study

site (Clarke and Gorley, 2001). Bray Curtis similarity for species diversity for all the species

belonging to zooplankton, macrobenthos, shell fishes and fin fishes was determined

analytically by using PRIMER-v5 software package.

Plate No. 1: GOOGLE MAP SHOWING THE STUDY AREA

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Figure 1: Map showing the location of the study stations in the Mangrove

Ecosystems in the Kali Estuary, Karwar

STUDY STATIONS:

#1: Mavinahole Creek #3: Sunkeri #5: Kinnar

#2: Kanasageri #4: Kadwad

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Plate 2: STUDY STATIONS

Stn.1 Mavinahole Creek

Stn.2 Kanasgiri

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Plate No. 3: STUDY STATIONS

Stn.3 Sunkeri

Stn.4 Kadwad

Stn.5 Kinnar