Temperature magnified postcapture mortality in adult sablefish after simulated trawling

Abstract

For sablefish Anoplopoma fimbria that had been transferred abruptly from ambient (5·7 C) to temperatures ranging from 15 to 20 C for 30 min followed by 15 min in air (19·5 C), mortality increased with temperature. Mortality occurred at lower temperatures for sablefish that were net-towed for 4 h at ambient temperature before exposure to a rapid increase in temperature. A clear relationship was apparent between serum lactate and temperature with lactate increasing as temperature increased. For treatments in which mortality did not occur, lactate decreased sharply within 24 h, suggesting recovery. It would appear that the critical postcapture temperature for sablefish that reside and are captured at 4-6 C, would be between 12 and 15 C. The results of this study suggest that fishery management strategies designed to increase postcapture survival of sablefish bycatch should include a consideration of the impact of exposure to seasonal thermoclines and seasonally elevated air temperatures.

Escape mortality of trawl caught Baltic cod (Gadus morhua) — the effect of water temperature, fish size and codend catch

“…Thus, the rise of temperature may have been up to 8-10 • C during the last minutes of the tow. An abrupt and several degrees of rise in temperature induced high mortality in adult sablefish, Anoplopoma fimbria (Olla et al, 1998).…”

Assessing the factors influencing discard mortality of demersal fishes using a semi-quantitative indicator of survival potential

“…Prioritizing the sorting of catches to rapidly return species of conservation concern to the water, and reducing catch sizes, via reduced net size or activity duration, which in turn reduces sorting times (e.g., Wassenberg and Hill, 1989;Berghahn et al, 1992), are two possible approaches. The second potential mitigation measure would be restricting fishing to times of the year when water surface and air temperatures are lower or when waters are well mixed, since increased temperatures were associated with decreased condition in many taxa in this study and decreased survival in other studies (e.g., Jean, 1963;Olla et al, 1998;Olla, 2001, 2002). The third measure is the choice of fishing gear, with the ensuing circumstances surrounding how it is fished.…”

Stress induced by hooking, net towing, elevated sea water temperature and air in sablefish: lack of concordance between mortality and physiological measures of stress

“…Tel. : (541) 867 0256; fax: (541) 867 0136; email: michael.davis@hmsc.orst.edu Childress, 1994;Schisler & Bergersen, 1996) and marine fish (Barton & Iwama, 1991;Muoneke & Childress, 1994;Ross & Hokenson, 1997;Olla et al, 1998). Temperature can be one of the major controlling factors in the life history of fishes, exerting a critical influence on all aspects including survival (Brett, 1970;Fry, 1971).…”

“…When not targeted for capture, non-reproductive and reproductive sablefish are often part of the bycatch of other directed groundfish fisheries, using trawl or longlining methods (Rickey & Lai, 1990;Sampson et al, 1997). In warmer months of the year, there is a high probability that during gear retrieval, sablefish would be subjected to abrupt elevation in temperature that may induce acute levels of stress and ultimately, mortality beyond that associated with capture processes alone (Olla et al, 1998).…”