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Fisheries Behavioral Ecology
Research Topic 3: Simulate Potential Mortality Factors

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Circular tank and net-towing apparatus

The second step is to simulate potential bycatch mortality factors in the laboratory and to conduct capture simulation experiments.  Mortality factors include: capture injury; light; temperature; air exposure; and effects of factor interactions.  Various experimental setups are used to simulate capture by hook and line and by net.  Seawater and air temperatures are regulated by large chillers and heaters and light conditions are controlled.

Circular tank and net-towing apparatus for simulation of fish towed in a trawl cod end.  Fish are towed at speeds up to 1.1 m/s in two nets attached to arms, which are rotated by a 5 horsepower motor and speed controller.  In the tank, light conditions (darkness to low light) and seawater temperature (1o to 14 oC) are controlled.

 

Capture simulation experiments are designed and conducted with potential bycatch mortality factors.  Fish are captured in the field and allowed to acclimate in the laboratory.  Acclimation includes resumption of feeding and normal activity at temperatures that the captured fish normally live in.

            Experiment with potential mortality factors

A flow chart for a typical capture simulation experiment with potential mortality factors.  Fish are taken from a holding tank and either hooked or towed for 4 hours.  Then fish are exposed to either 6o or 16oC seawater for 30 min, followed by exposure to 16oC air for 15 minutes.  Finally fish are returned to a recovery tank for up to 30 days to detect delayed mortality.  Immediate mortality is observed as fish are placed in recovery tanks.

 

Steps for Studying Bycatch Mortality in the Laboratory
[ Step 1] [ Step 2 ] [ Step 3 ] [ Step 4 ] [ Step 5 ] [ Step 6 ]

 

Research Topic 1: Fish and Environment

Research Topic 2: Fish Habitat

Research Topic 3: Bycatch Mortality

Research Topic 4: Fishing Gear

 

Last updated 27 March, 2009


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