Muscular Fatigue and Mortality in Haddock, Melanogrammus aeglefinus, caught by Otter Trawl

Abstract

Haddock were subjected to strenuous muscular exertion in capture by otter trawl. In each of seven tows, blood lactic acid followed a similar pattern with peak levels between 90 and 240 min after capture. Generally, in surviving fish, lactic acid subsided to preexercise levels within 12 hr after capture. Tagging fish immediately after capture had no demonstrable influence on lactic acid level during recovery. Among the seven tows, mortality associated with fatigue ranged from 0 to 27%. Mortality estimates were made for an additional nine tows. Where mortality was attributable to fatigue, lactic acid varied between 100 and 220 mg/100 ml, with a mean of 150 mg/100 ml. Percentage mortality ranged between 7 and 78.