Fish kill: Cause, Control and Impact Mitigation
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Transcript of Fish kill: Cause, Control and Impact Mitigation
FISH KILL: CAUSES, CONTROL AND IMPACT MITIGATION
Carlito R. Barril, Ph.D Professor of Chemistry (Retired)
UPLB
1
Presentation Outline Introduction Definition Selected fish kill events in the world
Causes of fish kill Types of fish kill Causal factors
Control measures Prevention and investigation Institutional measures Engineering measures
Mitigation of impact Proposed monitoring and warning system
Conclusions
2
Definition(s) Fish kill is defined as localized mass die off of fish that can occur in
marine, estuarine, or freshwaters (Meyer and Barclay, 1990)
Fish kill is a “sudden and unexpected mass mortality of wild or
cultured fish” (Lugg, 2000).
The term fish kill, known also as fish die-off and (in Britain) as fish
mortality, is a localized die-off of fish populations which may also be
associated with more generalised mortality of aquatic life.(Wikipedia)
A single fish kill event can number from several individuals to
millions of dead fish.
3
Definition(s)
Standard definition suggested (La and Cooke, 2011):
An event is considered a fish kill :
a) if the mortality event is not part of the fishes’ natural life cycle (e.g.,
mass mortality following spawning activity in semelparous fish);
(b) if a minimum of 25 dead fish are found in one square kilometre
(lentic) or river kilometre (lotic) and within a 48-hr period, and
(c) if mortality was not caused by predation, including by humans (i.e.,
harvest)
Thus , a single fish kill event can number from 25 to millions of dead fish.
4
Economic Impacts of Fish Kill
Significant economic loss for the fish farm owners
in case of open fishing areas - reducing the population of
recreationally and commercially valuable fish
Reducing source of fish protein available for humans.
cleanup costs
reduced tourism and recreation value
Affects usage of body of water for domestic water supply
Large fish kills also have a negative effect on regulation of food
web dynamics and nutrient balance .
5
Objectives To understand the causes of fish kills and why they occur in order to implement
preventive measures to reduce their frequency and magnitude. Specifically:
Review fish kill events in the world
Understand the different causes of fish kills
Determine the protocols employed in investigating, controlling and minimizing impacts of fish kills.
Propose a protocol for preventing and minimizing impact of fish kills in the Philippines focused on Laguna de Bay
6
Overview of fish kills in the world:
How widespread are the fish kills? Unfortunately, fish kill events are typical and occur worldwide.
Most fish kill events are not isolated, and tend to recur often
(Thronson and Quigg, 2008).
For example, North Carolina reports approximately30 fish kill
events per year since 1996 (NCDWQ, 200 ).
New South Wales reports an average of 34 fish kills per year,
(Koehn, 2004).
Reports of fish kill came also from Kenya (Ochumba, 1990),
Norway (Leivestad and Muniz, 1976), Brazil (Munoz et al.,
1994), United Kingdom,, Ireland, Australia, China, etc.
7
How widespread are the fish kills? In North America, a number of regional summaries of fish kill causes
were reported in Kansas, Missouri, Florida, and North Carolina, and a
national summary for the United States between 1980 and 1989
(Lowe et al., 1991).
Based on EPA data from 1977–1987, estimated 141 million fish die
per year nationally because of fish kills (Pimentel et al., 1993)
A review of all fish kill events that were summarized in both the peer-
reviewed literature and technical reports for North American estuaries
and freshwaters from 1890–2006 (excluding the summaries
produced by Kansas, Missouri, Florida, and North Carolina to avoid
regional bias) identified 170 fish kill events. (see Table 1
8
Table 1a. Some reports on frequency of fish kill events.
Place and date Ave. No. of fish kill
events/year No. of fish killed Reference
USA (1977–1987) >170 141 million per year Pimentel et al.,
1993.
North Carolina,
(1980s) 15 2.5 million Lowe et al., 1991
North Carolina,
USA, 1996 30 Not reported NCDWQ, 2000
North Carolina,
USA, 2008 61 7.5 M NCDWQ, 2008
New South Wales 34 (60-80) Not reported Koehn, 2004
New South Wales
(1980-1989) 16.6 Not reported Lugg, 2000
New South Wales
(1990-1996) 35.7 Not reported Lugg, 2000
Murray-Darling
Basin, Australia
(2002–2004)
3 >5,000 per event Koehn, 2004
9
Trend in number of fish kill reports in the newspapers worldwide
A search for the newspaper articles on fish kills printed in English
was conducted by La and Cooke (2011) covering articles
representative of over 350 major newspapers across North
America, Europe, Australia, Asia, and Africa.
From 1977 thru mid 1980’s - fish kills reported were <
50/year) (see Fig. 1)
Between 1987 - 1994, the number of reports rose steadily to
over 200/year.
By 1997, thru 2007 there were over 800 media reports on fish
kills annually
10
Fig. 1a. - Trend in number of fish kills reported in the newspapers worldwide
11
Table 1b. Selected fish kill events in the world
No. Event/Location Date Count
(Estimate) Species Cause/Remarks
1 Gulf of Mexico (Corpus
Christi)
1935, 22,000,000
Gulf
menhaden, strip
ed mullet,
various other
species[34]
Caused by red tide. This event
caused coughing ,sneezing and
watery eyes in humans. .
1986 22,000,000 Caused by red tide
2 Rhine River, Europe 1986 01 500,000 Caused by spill from Swiss
chemical warehouse.
3 Texas coast, USA 1997–1998 21,000,000 Caused by a bloom of Karenia
brevis
4 White River; West Fork,
Indiana, USA 1999 4,800,000
Caused by discharge of 10000
gallons of chemical HMP 2000 into
the river.
5 River Dee (United
Kingdom) 2002 07
100,000[38
]
salmon, trout, pe
rch
Unconfirmed link to release
of whey into river
6 Neuse River, North
Carolina, USA 2004 09 1,900,000 menhaden
] Natural upwelling of an
acknowledged polluted river.
Hydrogen sulfide smell reported.
7
Liuxihe
River Guangzhou Peopl
e's Republic of China
2008 09 09 10,000 carp Unknown[41][42]
12
Table 1b. Selected fish kill events in the world
No. Event/Location Date Count Species Cause/Remarks
8 Beaches at Thanet,
Kent, England 2010 01 20,000 velvet crab
dead crabs, starfish, lobsters,
sponges and anemones. Probably
killed by hypothermia.
9
Ting
River Fujian People's
Republic of China
2010 07
>1,000,000 Can
feed 70,000
people a year
Part of the Zijin mining disaster
10
Mississippi
River; Plaquemines
Parish, Louisiana, USA
2010 09 >1,000,000
redfish, trout,
pogies, drum,
crabs, shrimp,
BP oil discharge, High T & low tide
11
Jiaxing Xiuzhou
District People's
Republic of China
2011 01
06 250,000
bream, carp,
silver
carp, grass
carp
Only fish caught from a river
under China National Highway
320 east died.
12 Redondo Beach,
California, USA 2011 03 millions
anchovies, m
ackerel, sardi
nes and other
small fish
Caused by oxygen deprivation
13 Nordreisa, Troms,
Norway
2011 12
31 several tons herring [53][54]
14 Guangxi, People's
Republic of China
2012 01
15
40,000
kilograms Various
Caused by 2012 Guangxi cadmium
spill 13
Table 1b. Selected fish kill events in the world No. Event/Location Date Count Species Cause/Remarks
15 Laguna de Bay, Looc 1972, May 20 000 Milkfish Algal bloom of microcystis
16 Laguna de Bay, Central
Bay
1973,
June, July,
August
90% of stocks
killed in
several
fishpens
Milkfish Algal bloom, overstocking,
17 Laguna de Bay, Central
Bay
1975,
June, July
996 ha of
fishpens
affected,
5,000,000
Milkfish Algal bloom, overstocking,
18 Taal Lake, Luzon,
Philippines 2008 01 05
50 metric
tons Tilapia
May be linked to volcanic
activity and large fish farms
19 Taal Lake, Batangas,
Philippines 2011 05 29
750 metric
tons
Tilapia, milkfi
sh
Caused by oxygen depletion and
overstocking
20 Lingayen Gulf, Anda,
Pangasinan, Philippines 2011 05 30
500 metric
tons Milkfish
Oxygen depletion and change of
water climate
21
Laguna de Bay-Jala-jala,
Calamba, Sta. Cruz,
Pakil
2012, May-
June
>10 metric
tons, Not
counted
Tilapia, carp
DO depletion ; Unexplained dead fish
in open waters showed bruises and
cuts
14
Selected fish kill events in the world
Fig. 1b. Massive fish kill at Lake Elmer in Kingfisher Oklahoma, USA
15
Selected fish kill events in the world
Talisay: More than 800 tons of fish have died and rotted on fish farms in a lake near Taal volcano south Talisay: More than 800 tons of fish have died and rotted on fish farms in a lake near Taal volcano south Talisay: More than 800 tons of fish have died and rotted on fish farms in a lake near Taal volcano south Talisay: More than 800 tons of fish have died and rotted on fish farms in a lake near Taal volcano south Talisay: More than 800 tons of fish have died and rotted on fish farms in a lake near Taal volcano south Talisay: More than 800 tons of fish have died and rotted on fish farms in a lake near Taal volcano south Talisay: More than 800 tons of fish have died and rotted on fish farms in a lake near Taal volcano south
Fig. 1c. Massive fish kill in Plaquemines Parish,
West Missippi river, Louisiana USA. Sept. 2010
16
Selected fish kill events in the world
Fig. 1d. Close up of fish kill in Plaquemines Parish, Louisiana due to low tide
and high temperatures. BP oil discharge was also blamed.
17
Selected fish kill events in the world
Fig. 1e. Fish kill in West Pearl river, in New Orleans, LA.
August 17, 2011. Caused by black liquor discharge from a
paper plant. 18
Selected fish kill events in the world
Fig. 1f. Fish Kill in Dubuque, Iowa, linked to Dairy Farm Runoff. USA
19
Selected fish kill events in the world
Fig. 1g. Massive California fish kill. Estimated 1 Million Sardine
Carcasses /March 15th, 2011. Caused by depleted dissolved oxygen
level.
20
Selected fish kill events in the world
Fig. 1h. Large quantities of dead fish floats on Guanqiao Lake in Wuhan, Central
China's Hubei Province . July 11, 2007.
21
Selected fish kill events in the world
Fig. 1i. More than 800 tons of farmed fish in the northern Philippines died
suddenly after the water temperature rose. May, 2011
22
Selected fish kill events in the world
Fig. 1j. Thousands of milk fish float in a cage after a
massive fish kill at Taal Lake, Batangas.
23
Selected fish kill events in the world
Fig. 1k. Talisay: More than 800 tons of fish have died and rotted on
fish farms in Taal lake , Batangas. May-June 2011
24
Causes of Fish Kill
By and large, 66.9% of fish kills are caused by anthropogenic activities,
while only 10.1% were caused by natural events and
23% were undetermined. (NCDWQ,2000; Thronson and Quigg, 2008).
Table 2 shows the distribution of fish kill causes as follows: agricultural pollution (19.5%), biotoxins (17.2%), and chemical pollution (7.1%). Minor causes were extreme changes in temperatures (5.9%), low dissolved oxygen (5.3%), gas bubble trauma (3.6%), disease (3.6%), exhaustion (2.4%), and acidification (1.2%), and undetermined (23%).
25
Table 2a. Common Causes of Fish Kill Cause Frequency
Agricultural pollution - Pertains to pesticide, fertilizer and manure, silo and feedlot
drainage, animal waste, etc.—can be direct or lead to other problems, such as hypoxia
19.5%
Biotoxin - Toxic algal and dinoflagellate blooms that are caused by Karena brevis, Pfiestera, etc. 17.2%
Industrial pollution -Pollution arising from various resource extraction, processing, and
manufacturing activities (e.g., mining, food and kindred products, chemicals, metals, petroleum,
and paper products)
7.1%
Extreme temperature changes - Rapid changes in temperature (e.g., cold shock) 5.9%
Low dissolved oxygen (hypoxia or anoxia)- Low levels of oxygen in the water,
usually associated with urban runoff, algal bloom, decay of organic material (i.e., biological
oxygen demand), rainfall events, etc.
5.3%
Disease - Various bacteria, parasites, fungus, and viruses 3.6%
Gas bubble trauma - Gas-supersaturation downstream from dams or other infrastructure or
natural barriers
3.6%
Exhaustion -Physical exhaustion of fish typically leading to cardiac collapse (e.g., during
challenging migration)
2.4%
Acidification - Acidification by oxidation of sulphide minerals; can be delivered via
precipitation (e.g., acid rain)
1.2%
Municipal pollution - from refuse disposal, water system, swimming pools, power, and sewage
systems
Transportation pollution- Pollution that pertains to rail, trucks, barge or boats, and pipeline
ruptures
Unknown/undetermined - Fish kill events in which no cause can readily be determined 23% 26
Common causes of fish kill
Fish kills -first visible signs of environmental stress;
Common causes :
hypoxia or oxygen depletion,
diseases and parasites,
toxic substances and hazardous wastes,
temperature change,
overstocking,
underwater explosion, etc.
27
Causes of fish kill (Cont’d)
1. What is hypoxia or oxygen depletion ?
Hypoxia, or oxygen depletion, is a phenomenon that
occurs in aquatic environments as dissolved oxygen (DO)
level is reduced to a point where it becomes detrimental to
living aquatic organisms.
DO is typically expressed as % of O2 or mg/L dissolved at
prevailing temp. and salinity (Tables 2a &2b).
States of hypoxia in an aquatic environment is shown in
Table 2c.
28
What is hypoxia or oxygen depletion ?
Temp
DO at 100%
Saturation
DO at 80%
Saturation
DO at 30%
Saturation
oC mg/l mg/l mg/l
0 14.6 11.68 4.38
5 12.8 10.24 3.84
10 11.3 9.04 3.39
15 10.1 8.08 3.03
20 9.1 7.28 2.73
25 8.3 6.64 2.49
30 7.6 6.08 2.28
35 7 5.6 2.1
40 6.5 5.2 1.95
45 6 4.8 1.8
Table 2b. Solubility of oxygen in equilibrium with air in fresh
water (salinity 0) (at P = 1 Atm)
29
What is hypoxia or oxygen depletion ?
Temp
DO at 100%
Saturation
DO at 80%
Saturation
DO at 30%
Saturation
oC mg/l mg/l mg/l
0 11.2 8.96 3.36
5 9.9 7.92 2.97
10 8.8 7.04 2.64
15 7.9 6.32 2.37
20 7.2 5.76 2.16
25 6.6 5.28 1.98
30 6.1 4.88 1.83
35 5.6 4.48 1.68
40 5.3 4.24 1.59
45 4.9 3.92 1.47
Table 2c. Solubility of oxygen in equilibrium with air in sea (salt) water
(at P = 1 Atm)
30
What is hypoxia or oxygen depletion ?
State (Zone) DO Level
(%)
DO at 25oC & 1 Atm in sea water
(mg/L)
Remark
Anoxic or
anaerobic 0% 0 All fish and benthic
organism die
exaerobic >0<1% Boundary between
anoxic & hypoxic
zones
Hypoxic or
dysoxic 1 to 30% 0.07 to 1.98
(2.26 freshwater)
Most fish cannot live
below 30%
―Healthy‖ or oxic ≥80% 5.28
(6.64 freshwater)
5 mg/L is the water
quality criteria for DO
Table 2d . States of hypoxia in aquatic environment
31
Causes of fish kill (Cont’d)
How does algal bloom cause fish kill?
Algal bloom is a term used to describe the profuse growth of
aquatic algae.
It can occur in both fresh water and marine environments.
Algal blooms are often green, but can also be yellow-brown or
red, depending on the species of algae.
One common algal bloom is caused by the blue green algae,
microcystis sp., a cyanobacteria which may resemble a green
blanket covering a body of water during summer especially
when the water is calm. (see Figures )
32
Causes of fish kill (Cont’d)
How does algal bloom cause fish kill?
Fig. 2a. Algal bloom -The thick green waters of Lake Chaohu, China
33
Causes of fish kill (Cont’d)
How does algal bloom cause fish kill?
Fig. 2b. Algal Blooms - Midwest Lakes, USA
34
How does algal bloom cause fish kill?
DO level cycle during an algal bloom:
During the day, DO is high because of the photosynthesizing algae.
At nightime, DO is reduced by the aerobic respiration of all living organisms in the water (see Fig. 2a)
A diurnal cycle of DO level is thus observed, very high during the day and low towards the break of dawn.
Some fish might be distressed at this period but no deaths are yet observed.
35
Diurnal cycle of DO during photosynthesis and
Aerobic respiration
Fig. 2c Aerobic respiration (red arrows) during which both plants and animals
utilize oxygen to metabolize organic compounds that were created through
photosynthesis (green arrow).
36
How does algal bloom cause fish kill?
DO level cycle during an algal bloom:
When the algae bloom collapsed, i.e. the algae died, and sunk to the bottom where they are decomposed by facultative anaerobic organisms
First by facultative bacteria and later, when all DO is depleted, by anaerobic bacteria producing obnoxious products such as NH3 and H2S sulfide which are both highly toxic to fish (see Box #1).
Under these conditions, no fish or any other benthic organisms can live.
And if these bottom waters with zero DO and containing toxic NH3 and H2S are brought up by turnover or any mixing process, then fish kill will surely occur.(see Fig. 2a)
37
How does algal bloom cause fish kill?
Box # 1. Anaerobic decomposition products:
ORGANIC MATTER (C, H, O, N, P, S) Anaerobes CH4, NH3, H2S, CO2,VFA
38
How does algal bloom cause fish kill?
Figure 2d. A simplified model of a summer fish kill mechanism. Critical
levels indicate high fish kill risk. (After Barica 1973, 1975 b)
39
How does algal bloom cause fish kill?
Fig. 2e. Key Indicators before and after algal collapse:
• Secchi disc transparency is only 0.2–0.4 m at bloom phase
• DO high during bloom phase and falls abruptly during the algal collapse and decay
• chlorophyll “a” values of 100–200 ug/1 (algal bloom phase)
• Ammonia at near-zero level starts to increase and reaches maximum after DO drops to zero.
• pH follows DO, high during bloom phase and low during algal decay.
40
Ammonia toxicity to fish Among the effects are:
loss of equilibrium,
Hyper-excitability,
increased breathing,
decrease in nitrogen excretion, not to mention death.
At lower concentrations: reduced hatch and reduced growth rates.
Percentage of toxic un-ionized NH3 vs. NH4+ ion increases with Temp but decreases with pH.
At pH 8.5, - %NH3 is 15.3 at 25oC. and 20.3 at 3ooC
At 3ooC , - %NH3 is 7 at pH 8.0 and 2.48 at pH 7.46
However, toxicity of NH3 increases with decreasing pH. (see Table 2e)
41
Table 2e. Lethal ammonia concentrations for salmon at 86 degrees 30oC (by
pH, and duration of exposure) (EPA, 1985).
pH Duration Lethal* Ammonia Concentration
(mg/l)
Total NH3 Un-ionized NH 3
6.5 1-hr
4-hr
14.3
0.73
0.036
0.002
7.0 1-hr
4-hr
11.6
0.74
0.093
0.006
7.5 1-hr
4-hr
7.3
0.74
0.181
0.019
8.0 1-hr
4-hr
3.5
0.47
0.27
0.035
8.5 1-hr
4-hr
1.3
0.17
0.26
0.035
*LC50 levels at which half of the exposed individuals die. U.S. EPA recommends that these levels should not be exceeded more than once in three years.
42
Common Name Scientific Name Avg Species LC50
(ug/L) LC50 Std Dev Avg Species Rating
Goldfish Carassius auratus 58.4 31.1 Very Highly Toxic
White sucker Catostomus
commersoni 23.4 6.32 Very Highly Toxic
Lake whitefish Coregonus
clupeaformis 15.3 25.9 Very Highly Toxic
Northern pike Esox lucius 38.7 26.9 Very Highly Toxic
Asian redtail catfish Hemibagrus
nemurus 3.20 - Very Highly Toxic
Bluegill Lepomis
macrochirus 23.1 12.3 Very Highly Toxic
Largemouth bass Micropterus
salmoides 78.1 82.5 Very Highly Toxic
Rainbow
trout,donaldson
trout
Oncorhynchus
mykiss 38.0 38.3 Very Highly Toxic
Yellow perch Perca flavescens 35.6 43.4 Very Highly Toxic
Fathead minnow Pimephales
promelas 57.3 93.2 Very Highly Toxic
Brown trout Salmo trutta 7.00 - Very Highly Toxic
Walleye Stizostedion
vitreum 42.0 21.7 Very Highly Toxic
Table 2f. Toxicity of hydrogen sulfide to fishes.(EPA database).
43
How does turnover cause fish kill?
How does heavy rain cause fish kill?
Lake is stratified with high DO in upper layer
(epilimnion) and low DO at the lower layer
(hypolimnion)
During turnover the heavy cold
rainwater sinks causing a mixing of the
two layers
44
How does algal bloom cause fish kill?
Red tide or harmful algal bloom (HAB)
•Algal bloom that causes negative impacts to other
organisms via production of natural toxins, mechanical
damage to other organisms, or by other means.
•HABs are often associated with large-scale marine
mortality events and have been associated with various
types of shellfish poisoning. (see Table )
•Of the 5000+ species of marine phytoplankton that exist
worldwide, about 2% are known to be harmful or toxic.[6]
45
Causes of fish kill (Cont’d)
How does algal bloom cause fish kill?
Fig. 2f. Red tide or Harmful Algal Bloom
46
Causes of fish kill (Cont’d)
How does algal bloom cause fish kill?
Fig. 2g. Red tide or Harmful Algal Bloom
47
How does algal bloom cause fish kill?
Examples of common harmful effects of HABs:
•production of neurotoxins which cause mass mortalities in fish,
seabirds, sea turtles, and marine mammals
•human illness or death via consumption of seafood contaminated
by toxic algae
•mechanical damage to other organisms, such as disruption of
epithelial gill tissues in fish, resulting in asphyxiation
•oxygen depletion of the water column (hypoxia or anoxia) from
cellular respiration and bacterial degradation
48
How does algal bloom cause fish kill?
Toxin HAB species Affected Organisms Remark /effects
Brevetoxins
dinoflagellate Karenia brevis bottlenose dolphins,
manatees, whale
neurotoxin responsible
for neurotoxic shellfish
poisoning
Saxitoxin
dinoflagellate Alexandrium
fundyense
cyanobacteria Anabaena sp
Finfish, shellfish neurotoxin responsible
for paralytic shellfish
poisoning
Domoic Acid
Diatom Pseudo-nitzschia, Mammals, human neurotoxin responsible
for amnesic shellfish
poisoning
Cyanotoxins cyanobacteria (also known
as blue-green algae)
Microsystis, Anabaena,
Planktothrix (Oscillatoria),
Nostoc, etc.
Fish, birds, livestock,
domestic animals
and sometimes
humans.
neutrotoxins,
hepatotoxins,
cytotoxins,
microcystins, and
endotoxins.
Table 2e . Toxins associated with red tides (HABs)
49
Causes of fish kill (Cont’d) 2. Diseases and parasites
Major types of fish diseases
1. Infectious diseases- caused by viruses, bacteria and
fungi
2. Invasive diseases – caused by parasites such as
protozoans, flukes and worms, or crustaceans.
Fish that are stressed for other reasons, such as spawning or
suboptimal water quality, are more susceptible.
In fish farming, where populations are optimized for the
available resources, parasites or disease can spread quickly
50
Causes of fish kill (Cont’d) Diseases and parasites
Pathogens which can cause fish diseases comprise:
viral infections
bacterial infections, such as Pseudomonas fluorescens leading
to fin rot and fish dropsy
fungal infections
water mould infections, such as Saprolegnia sp.
metazoan parasites, such as copepods
unicellular parasites, such as Ichthyophthirius multifiliis
51
Causes of fish kill (Cont’d) Effects of diseases and parasites
Some early warning signs :[10]
Discoloration, open sores, reddening of the skin, bleeding, black
or white spots on the skin, missing scales or lack of slime
Abnormal shape, swollen areas, abnormal lumps, or popeyes
Abnormal activity such as flashing, twisting, whirling,
convulsions, loss of buoyancy
Listlessness, weakness, sluggishness, lack of activity
Loss of appetite or refusal to feed
52
Causes of fish kill (Cont’d)
3.Toxic substances and hazardous wastes
Sources include:
agricultural runoffs carrying pesticides, fertilizers, etc.
industrial wastes containing toxic chemicals and hazardous
wastes such as toxic heavy metals, acidic process waters,
etc.,
hazardous spills such as petroleum products,
Sewage surface runoff containing high organic load
53
Causes of fish kill (Cont’d)
Toxic substances and hazardous wastes
Human-induced fish kills are unusual, but occasionally a spilled
substance causes direct toxicity or a shift in water temperature
or pH that can lead to fish kill.
Some notable fish kills in Louisiana in the 1950s were due to a
specific pesticide called endrin.[
in 1997 a phosphate plant in Mulberry, Florida, accidentally
dumped 60 M gallons of acidic process water into a creek,
reducing the pH to less than 4, resulting in the death of about
1.3 million fish.[7]
About a million of fish died after an accidental spill of bourbon
whiskey into the Kentucky River. However, officials could not
determine whether the fish kill was due to the bourbon directly or
to oxygen depletion that resulted when aquatic microbes rapidly
began to consume and digest the liquor.[7]
54
Causes of fish kill (Cont’d)
Toxic substances and hazardous wastes
In 1999, about 5 million fish died in White River, Indiana caused
by an automotive parts maker which had discharged 10,000
gallons of the chemical HMP 2000 into the river.
In Jan. 2012, about 40,000 kg of fish died in Guangxi, People's
Republic of China caused by cadmium spill in a river.
Cyanide is a particular toxic compound that has been used to
poach fish. In cyanide poisoning the gills turn a distinctive cherry
red.
Chlorine introduced as alkaline hypochlorite solution is also
extremely toxic leaving pale mucilaginous gills and an over-
production of mucilage across the whole body.
55
Causes of fish kill (Cont’d)
4. Climate change: drought & temperature change
Fish kills can also result from a dramatic or prolonged drop
in air (and water) temperature.
This kind of fish kill is selective – usually the dead fish are
species that cannot tolerate cold.
Tilapia are unable to survive in temperate climates because
they require warm water. Most species of tilapia will die at a
range of 52 to 62 °F (11 to 17 °C).
56
Causes of fish kill (Cont’d)
Climate change: drought & temperature change
A fish kill can occur with rapid fluctuations in temperature or sustained high temperatures.
A period of sustained high temperatures can lead to decreased DO in a body of water.
An August, 2010, fish kill in Delaware Bay was attributed to low oxygen as a result of high temperatures.[23]
In September, 2010, a massive (millions) fish kill at the mouth of the Mississippi River in Louisiana, was attributed to a combination of high temperatures and low tide. BP oil discharge was also blamed.
57
Selected fish kill episodes in the world
Fig. 2d. Massive fish kill in Plaquemines Parish, West Missippi river, Louisiana, Sept. 2010 due to low tide and high temperatures.
58
Causes of fish kill (Cont’d)
5. Droughts and overstocking
A drought can lead to lower water volumes to the extent that the reduced volume may not be enough for the fish population.
Droughts often occur in conjunction with high temperatures so that DO level is also reduced.
Low river flows also reduce the available dilution for permitted discharges of treated sewage or industrial waste.
The reduced dilution increases the organic demand for oxygen further reducing the oxygen concentration available to fish.
Overstocking of fishpen can also result in fish kills!!!
59
Causes of fish kill (Cont’d)
6. Underwater explosions and emissions
Underwater explosions can lead to fish kill, and fish with swim
bladders are more susceptible.
Sometimes underwater explosions are used on purpose to
induce fish kills, a generally illegal practice known as blast
fishing.
Underwater explosions may be accidental or planned, such as
for construction, seismic testing, mining or blast testing of
structures under water.
Volcanic emissions resulting in the release of H2S which is very
toxic to fish.
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CONTROL AND PREVENTION OF FISH KILL
Knowing and understanding the different causes
of fish kill, how can we control or prevent them?
First we start with those factors caused
anthropogenically which comprised about 80% of
all causes.
Foremost among this is anoxia caused by
several factors such algal bloom, dumping of
high BOD wastes like sewage, garbage, oil, etc.
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CONTROL AND PREVENTION OF FISH KILL
1. Control of hypoxia or oxygen depletion
When algal bloom is apparent, reduce algal bloom density by
chemical treatment using herbicide/algaecide, to maintain SD
transparency above 60 cm.
Do not kill all the algae but treat 1/3 of your pond/farm at a time
and avoid treatment on extremely hot sunny days. Treat early
before the onset of calm summer days before April.
Do not overstock fish.
Avoid over feeding. Use feeding trays to minimize unused feeds
from falling down to the bottom.
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CONTROL AND PREVENTION OF FISH KILL
Control of hypoxia or oxygen depletion (cont’d)
Prevent or minimize surface run-off of wastes with high BOD load into your immediate surroundings.
Check BOD load of sediment under the fishpen area and make sure it does not exceed the WQ criteria.
Monitor key WQ parameters such as DO, SD, pH, T, NH3 , Chla.
Check DO level daily at the break of dawn during summer or when nearing harvest time.
Install an emergency aeration system – either subsurface or surface aerators to maintain DO level above 4 mg/L.
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CONTROL AND PREVENTION OF FISH KILL
2. Control of fish disease and parasites
General knowledge of fish disease control:
Focus on prevention rather than treatment.
Knowledge of what pathogens and parasites affect the stock. (see Fig. 4a)
Sanitation practices to prevent infection or introduction of pathogens and parasites.
Regularly check presence of disease and parasites
Diagnosis and treatment of fish diseases
Get services of a fish disease specialist or veterinarian
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Control and prevention of fish kill
Fig. 4a. Control of diseases of Tilapia – pathogens at different stages of culture
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3. Protocol for Prevention and investigation
A major problem with current fish kill investigations is that there is no globally accepted standard protocol.
Many countries in the developed world have specific provisions in place to encourage the public to report fish kills[30] so that a proper investigation can take place.
Investigation of the cause of a kill requires a multi-disciplinary approach including: a) on-site environmental measurements,
b) investigation of inputs,
c) review of meteorology and past history,
d) toxicology,
e) fish autopsy,
f) invertebrate analysis and
g) a robust knowledge of the area and its problems.
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Protocol for Prevention and investigation One good protocol to follow is the national investigation and reporting
protocol by the Commonwealth of Australia (2007).
It sets a standard minimum requirements for each stage of management of a fish kill incident and includes:
a) useful flowcharts,
b) information on sampling methods,
c) the roles and responsibilities of officers assigned to fish kills investigation, and
d) resources for investigating officers.
Some states in the USA have their own protocols for fish investigations, but these are localized in approach and difficult to adopt by less developed countries.
In view of this, La and Cooke (2011) proposed a framework for a more scientific and systematic approach to fish kill investigation, determining the proximate and ultimate causes and promulgating action plan for its prevention and impact mitigation that can be adopted worldwide (Table 3a).
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Table 3a. Framework for fish kill investigation (adopted from Meyer
and Barclay, 1990) Generalized
Investigation Steps
Current Status and Challenges Opportunities for Improvement
1. Fish kill reported/
suspected
by fax, mail, or telephone by
public
Can be tedious and time-
consuming
Time lag between fish kill
notification and scientific
investigation
Reporting by web-based submission or
phone call using fish kill hotlines
Reduce time lag between fish kill
notification and scientific investigation
2. Investigator
designated
Often regional biologist with
little expertise on fish kill
investigation
Create training programs for two sets of
investigators (1) First responder:
general knowledge of fish kills and
ability to take samples (2) Specialist:
specialized in fish kill research and has
knowledge of all assessment methods
and investigative tools
3. Site visit for
reconnaissance
Few visits per kill; often delayed or
non-existent
Implement long-term monitoring
programs
No standard protocol
Require more site-visits per kill
immediately after fish kill is
reported/suspected
Create standard protocol
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Generalized
Investigation Steps
Current Status and Challenges Opportunities for Improvement
4 Collect chemical, physical, and biological samples
Often delayed resulting in
degraded samples
Few samples taken
No control to compare pre-
fish kill to post-fish kill
Conditions
Implement long-term monitoring
programs
Take more samples, taking into
account biological Variation
Consider using reference sites
Adopt interdisciplinary approach
5 Fish kill count to
evaluate resource
damage and
monetary value
assessment
Often underestimated
Scavengers remove
carcasses
Economist value
assessments on species for
compensation costs
Take into account scavengers and
difficulties in detecting dead fish
Continue value assessments of
species and number of fish killed for
compensation
Conduct studies to understand
counting biases
6 Laboratory analysis
and database
mining
Samples often degraded or
limited; difficult for
pathological analysis
Collection of more samples
immediately after fish kill reported
Adopt interdisciplinary approach in
data analysis
Table 3a. Framework for fish kill investigation (Cont’d.)
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Table 3a. Framework for fish kill investigation (Cont’d.)
Generalized
Investigation Steps
Current Status and Challenges Opportunities for Improvement
7. Collate and
synthesize
information
Information prior to fish kill
unavailable, difficult to determine
causation
Most investigations try to identify a
single cause, but in reality rarely reveal
more than correlation
Consider several factors as most
fish kill causes are complex
Consider carry-over effects
8 Prepare a report Non-existent in some jurisdictions,
while others compile annual regional
reports
Implement annual reporting on
regional/national/global levels on
fish kills
Publish case studies in peer-
reviewed outlets
9 Regulatory or
management
action response
to those causes
• Some monitoring; most do not have
fish kill management plans
• Reactive approach to fish kills rather
than attempting to predict and prevent
events
• Implement long-term monitoring
programs
• Identify potential causes and
structure management action in
response to those causes
• Adopt a proactive approach to
fish kill prevention
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National Protocol for prevention and investigation of fish kill
In line with the framework proposed above, the Philippines
should strive to formulate a national protocol for investigation
and prevention of fish kills.
The national agencies and instrumentalities involved in the
management of our aquatic and marine resources such as the
PCAMRD, BFAR, DENR, LLDA, etc. should collaborate for the
formulation of the national protocol.
In the mean time, I would venture to propose a fish kill
management framework plan for Laguna de Bay
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Framework Plan for the Control and Impact Mitigation of
Fish Kill in Laguna de Bay
This plan consists of two phases:
Phase 1. Review and Cause Analysis of Fish Kills in Laguna de Bay and Other Places
Based on this review, the causal factors will be identified,
classified, and their specific effects will be ascertained
based on observation and scientific findings.
For quantifiable factors the critical level of toxicity to fish and
other impacts will be determined from published data.
Table 1 shows the different factors to be considered.
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Framework Plan for the Control and Impact Mitigation of Fish Kill in Laguna de Bay
Phase 1: Table 1 - Data and information to be collected
1. Spatial data and stocking density
Location of fish kill
Density of fish pens in the lake (% of surface area, by location i.e. East, West, or
South Bay)
Stocking rate (number of fingerlings per square meter)
Feeding practice (method, frequency and quantity per stocking load)
Water depth in the affected area
Proximity to anthropogenic sources of toxic pollutants (nearby factories, industrial
establishments, agricultural runoffs, sewage & garbage disposal, etc.)
2. Temporal data
What season of year fish kill occurred
Which months fish kill more prevalent
Duration of fish kill
3. Fish health data
Occurrence of fish diseases
Presence of parasites
Other threats to fish health such as toxins, knifefish attacks, etc.
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Framework Plan for the Control and Impact Mitigation of Fish Kill in Laguna de Bay
Phase 1: Table 1 (Cont’d) 4. Water Quality Data –Trend in the bio-physicochemical parameters in the last
20 years
Dissolved oxygen (DO)
Biochemical /chemical oxygen demand (BOD/COD)
Temperature
pH
Secchi disc readings
Chlorophyll a
Seasonal variation
5. Hydrological/Meteorological data
Water currents in the lake, seasonal changes,
Rainfall (monthly and annual data)
Wind direction (moonsons – months & duration)
Etc.
6. Carrying Capacity Study of Laguna de Bay
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Framework Plan for the Control and Impact Mitigation of Fish Kill in Laguna de Bay
Phase 2: Development of a monitoring and warning system for preventing fish kill
Based on the results of Phase 1, a model monitoring and warning system that could prevent or
signal an impending fish kill will be developed, tested and deployed in strategic places.
Pending the results of Phase 1 study, the conceptual framework for this monitoring system is
envisioned to have four components:
a) a set of policy and regulatory measures and guideline on fishpen zoning, stocking density,
feeding rate and frequency;
b) monitoring of key water quality parameters such as pH, Temperature, DO, BOD/COD, Total
Ammonia, Secchi disc reading, and Chlorophyll a or algal growth,
c) Fish health management measures, and
d) stakeholders and communication network.
A set of critical values for key water quality parameters will be formulated to serve as warning or
alert levels to institute remedial measures before a critical condition for fish kill is reached.
Table 2 shows the conceptual framework for the monitoring and warning system.
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Phase 2: Table 2 Conceptual Framework for the Monitoring and Warning
System for Fishkill Prevention
Factors Guideline
1. Policy and regulatory measures to be imposed and monitored
Fish pen zoning - based on
physiographic and hydrological data
Total fishpen area – based on carrying
capacity data
Stocking density – must not exceed the
optimum or maximum prescribed by
BFAR
Feeding practice –method, frequency,
quality and quantity of feeds,
Where to locate, density of fishpens
What is total fishpen area to be allowed
in the Lake?
Maximum number per cubic meter
Feeding method, frequency rate, quality
and quantity of feed per fingerling,
2 Fish health management measures
Fish disease prevention and detection
Parasites control
Fish farm sanitation practice
Aerators
How to detect and prevent fish diseases
How to control parasites
Proper sanitation practices
Need for aerators
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Phase 2: Table 2 (Cont’d) Factors Guideline
3. Monitoring of key water quality parameters to detect critical levels*
pH
Temperature
Dissolved Oxygen
BOD/COD
Total Ammonia
Secchi disc transparency (Turbidity)
Chlorophyll a or algal growth
6.5 -8.5
Ambient ± 3oC
>5.0 mg/L
< 10/20 mg/L
0.17- 0.73 mg/L (pH & T dependent)
20 -40 cm (Class C criteria=100 cm)
< 100 μg/l (as chlorophyll “a”) ,
How to prevent algal bloom
4. Stakeholders and communication network
Involvement of stakeholders - (LLDA, LGUs,
Fishpen owners, fishermen, etc.)
Mass education of the people on the scientific
aspect and risk involved
Communication network to enhance
exchange of information among stakeholders
involved
Led by LLDA or a management group
Proper education of the people especially
fishermen and fishpen operators
Set up an early warning system based on
modern communication facilities.
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CONCLUSIONS Review of fish kills events revealed a widespread and worldwide occurrence
of this phenomenon in both freshwater and marine environments.
A survey of fish kill reports in 350 major newspapers representing the major continents except South America shows an exponential increase from less than 50 fish kill events per year in the 1970s to about 900 events per year in the 1990s before leveling off beyond year 200.
Determination of the causes of fish kills shows that majority (about 70%) are due to anthropogenic activities with only 10.1 % due to natural events, while 23% were unknown or undetermined.
Agricultural pollution topped the list of anthropogenic causes with 19.5% followed by biotoxins from harmful algal blooms with 17.2% and the rest with contributions below 10 %.
Extreme temperature changes, either too hot or too cold, is the top natural cause of fishkill.
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CONCLUSIONS (Cont’d) The common ultimate cause of fish kill reported is low DO (hypoxia or
anoxia) which is associated with urban runoff, algal bloom, decay of organic material, rainfall events, drought and prolonged high temperature, etc.
The common control or preventive measures for fish kill are algal bloom prevention, prevention of runoffs with high BOD load, no overstocking, no overfeeding, detection and treatment of fish diseases and parasites, and installation of emergency aeration systems.
The need for the formulation of a national protocol for investigation and prevention of fish kills is suggested.
A framework plan for the development of a monitoring and warning system for the prevention of fish kills in Laguna de Bay is proposed.
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SALAMAT PO
THANK YOU
ARIGATU GOSAIMAS DESU
SALAMAT PO
THANK YOU
Arigatōgozaimashita
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Have a blessed day!
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St. Peter’s Fish
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