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Fisheries Behavioral Ecology
Research Topic 3: Understanding and Predicting Bycatch Mortality Using a Laboratory Approach

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Picture of bycatch being discarded from a shrimp trawl catch

Picture of bycatch being discarded from a shrimp trawl catch.

 

The Fisheries Behavioral Ecology Program has developed unique laboratory tools and experimental protocols for studying the effects of fishing-related stressors on fish bycatch mortality.  Fishing practices ordinarily involve allowing undersized and unwanted fish (bycatch) to escape from fishing gear (escapees) or to be returned to the sea (discards) after being brought onto a fishing vessel.  Total mortality of bycatch can be an important component of fishing mortality in stock assessment models.  Estimation of total mortality requires knowledge of both immediate (after fish escape or are brought onto the boat) and delayed mortality in escapees and discards.  Delayed mortality can result from injury, disease, predation, and loss of feeding.  For more information about this research and issues regarding bycatch, see our Quarterly Report feature article on Understanding Fish Bycatch Discard and Escapee Mortality

See a video on fish discard mortality.

Chart of steps for studying bycatch mortality in the laboratory Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 [ Step 1] [ Step 2 ] [ Step 3 ] [ Step 4 ] [ Step 5 ] [ Step 6 ]

A diagram of steps for laboratory study of bycatch mortality.  Click on individual boxes to see details of each step.

The study of bycatch mortality in the laboratory can be viewed in a series of steps.  The investigator moves from a conceptual model of bycatch mortality, through understanding what factors cause mortality, to the use of bycatch prediction tools in field fishing experiments.  Traditional studies of bycatch mortality have used fishing experiments to measure immediate and delayed mortality of discards and escapees that were captured and held in sea cages or tagged and recaptured.  Rates of experimental mortality were then correlated with fishing conditions and potential bycatch mortality was modeled statistically.  The disadvantages of this field approach are that fish must be held or monitored for long periods of time in the field, and few experiments can be conducted because of the complex logistics for holding fish.  Here we describe a laboratory approach which identifies fishing stressors that potentially cause mortality and leads to the development of more efficient methods for conducting field fishing experiments.

 

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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