Subject: Fish Discard Mortality: Sources, Prediction, and Reduction (video)
Speaker: Michael W. Davis, AFSC, Hatfield Marine Science Center
When: Thursday, 19 January 2006 noon-1:00
Where: NOAA Sand Point Campus, 7600 Sand Point Way NE, Seattle;
Bldg 9
Dear Colleagues: We’re pleased to offer you the first installment of
the new AFSC Seminar Series, which highlights center-wide research
relevant to ecosystem management.
Fish Discard Mortality: Sources, Prediction, and Reduction
Michael W. Davis
Alaska Fisheries Science Center, RACE Division
Fisheries Behavioral Ecology Program,
Hatfield Marine Science Center, Newport, Oregon
Abstract
The development of direct methods to predict
discard mortality in fishing operations is essential for effective
conservation of sensitive fish stocks. Currently, discard mortality
rates in most fisheries are the result of educated guesses with little
or no data. For a few fisheries, discard mortality data are available
from fishing experiments in the field or laboratory that describe the
bounds of effects from fishing stressors, but suffer from low
resolution. A more direct approach to predicting discard mortality
entails establishing relationships between fish condition and mortality
and then measuring the condition of fish discards from a wide range of
fishing operations. Prediction of discard mortality in stock assessments
that uses actual fishing conditions as inputs would greatly increase the
accuracy of estimates for this source of fishing mortality. Results from
laboratory studies in Newport have shown that behavior impairment
(decreased reflex responses) can predict total mortality with sigmoid
relationships that are species-specific and related to the severity of
stressors and stressor combinations. These predictive relationships
incorporate the effects of wounding and environmental factors over a
range of fish sizes, acting as integrative expressions of stressor
effects typically present in fishing. The measurement of behavior
impairment and wounding on board fishing vessels to estimate discard
mortality appears feasible and would greatly increase the scope of
fishing conditions that could be investigated.
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