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

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https://ir.library.oregonstate.edu/concern/articles/1j92gc23b

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  • 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 expected, lingcod from an average duration tow showed decreased survival with increased time on deck, though still had 50% survival after 30 min. This study suggests that discard mortality of lingcod is determined mainly by on-deck sorting and can be minimized by releasing fish quickly upon capture. Accurate estimation of mortality rates for lingcod will depend on the documentation of normal fishing behavior and on-deck sorting procedures.
  • Keywords: lethal limits, Ophiodon elongatus, trawling, bycatch
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  • Parker, S. J., Rankin, P. S., Hannah, R. W., & Schreck, C. B. (2003, May). Discard mortality of trawl-caught lingcod in relation to tow duration and time on deck. North American Journal of Fisheries Management, 23(2), 530-542.
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  • 23
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