Journal Article

Simulated fishing experiments for predicting delayed mortality rates using reflex impairment in restrained fish

M. W. Davis

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 64, issue 8, pages 1535-1542
Published in print November 2007 | ISSN: 1054-3139
Published online June 2007 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1093/icesjms/fsm087
Simulated fishing experiments for predicting delayed mortality rates using reflex impairment in restrained fish

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Davis, M. W. 2007. Simulated fishing experiments for predicting delayed mortality rates using reflex impairment in restrained fish. – ICES Journal of Marine Science, 64: 1535–1542.

Development of efficient methods to predict discard and escapee mortality in fishing operations is essential to the conservation of sensitive fish stocks. For a few fisheries, mortality data are available from fishing experiments in the field; these require long-term holding or monitoring of fish in tanks, cages, or tag and recapture experiments to detect delayed mortality. A different approach to predicting discard and escapee mortality is to use reflex action mortality predictors (RAMP) consisting of relationships between mortality and reflex impairment for species of interest. Fish were towed in a net in the laboratory and then either restrained in foam-lined holders and rapidly tested for reflex impairment five minutes after towing, or held for up to 60 days to determine delayed mortality. Delayed mortality occurred up to 20 days after towing. RAMP was related to mortality with biphasic sigmoid functions. As fishing stressors increased in intensity, the first phase showed an increase in RAMP with no concomitant mortality. In the second phase, RAMP continued to increase, while mortality became apparent and increased. The measurement of RAMP in restrained fish on board fishing vessels during experiments to predict discard mortality and in caged free swimming fish to predict escapee mortality is feasible and advisable.

Keywords: delayed mortality; fish condition; reflex impairment; salmon; stress; survival

Journal Article.  5625 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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