Discard Mortality of Trawl-Caught Lingcod in Relation to Tow Duration and Time on Deck

Abstract

Abstract The lingcod Ophiodon elongatus is a benthic marine fish commonly caught by groundfish trawlers and discarded due to low catch limits. Managers must account for the mortality of bycatch to assess population status accurately. Our objectives were to estimate the actual mortality of trawl-discarded lingcod (50–84 cm) and describe their physiological stress response to capture. We investigated three major factors of the trawling operation that may influence lingcod survival: tow duration, fish size, and the amount of time fish were on the deck of the vessel. Survival was monitored for 21 d and each surviving animal was then physically and physiologically evaluated. The results showed that regardless of the duration of the tow, lingcod survival was 100% for animals discarded immediately after the cod end was emptied on deck. All lingcod captured during a tow of average commercial duration demonstrated a maximal stress response, measured by plasma cortisol, glucose, and lactate concentrations. As expec...