Escape mortality of cod, saithe, and haddock in a Barents Sea trawl fishery

Abstract

Ingólfsson, Ó. A., Soldal, A. V., Huse, I., and Breen, M. 2007. Escape mortality of cod, saithe, and haddock in a Barents Sea trawl fishery. – ICES Journal of Marine Science, 64: 000–000. We investigated the survival of gadoid fish in the Barents Sea escaping from a demersal trawl during commercial fishing conditions, with and without a sorting grid, at high and low levels of fishing intensity. The mortality of cod and saithe was negligible and unrelated to experimental conditions. Haddock mortality was generally greater than observed in earlier experiments and inversely related to fish length. Any possible effects of experimental conditions were hidden by large variability in the observed rates of mortality. We conclude that the observed mortality of haddock is confounded by methodological problems, particularly the instability of the observation cages, and does not reflect the true escape mortality. Cod and saithe are capable of surviving the stress of passage through, and escape from, the trawl, whereas haddock are more vulnerable, despite being a closely related species.

A Preliminary Study on the Survival of Brown Comber, <I>Serranus Hepatus</I> (Actinopterygii, Perciformes, Serranidae), Escaping from the Codend of a Bottom Trawl

“…(Ryer et al 2004) like brown comber in the present study. Ingólfsson et al (2007) also reported such differences of mortality among three fish species that although cod and saithe (Pollachius virens) were capable of surviving after their escape from the trawl, haddock was more vulnerable. It was clear that brown comber have high capability of surviving after escape from the cod-ends.…”

“…Improving the selectivity of fishing gear to reduce the bycatch and discards has been one of the main management tools for sustainable fisheries (Tosunoğlu 2003a, Suuronen 2005, Ingólfsson et al 2007). Although in trawl fishery it is allowed that considerable amount of fish escape passing through trawl cod-ends, the process will only work effectively if escaping fish could survive (Breen 2004, Suuronen 2005.…”

“…For this reason, investigating the survival probability of escaping fish is a vital to assess a part of unaccounted fishing mortality. The escape mortality of some commercial fish, particularly haddock (Melanogrammus aeglefinus) (see Main and Sangster 1990), whiting (Merlangius merlangus) (see Sangster et al 1996) and Atlantic cod (Gadus morhua) (see Suuronen et al 2005, Ingólfsson et al 2007), had been studied over the past 15 years. The interaction between the observed mortality of those species and some factors (e.g., fish size, species, mesh size and shape, and water temperature) had been investigated (Main andSangster 1990, Ingólfsson et al 2007).…”

“…A considerable amount of studies of escape mortality have been conducted over the past two decades (Main and Sangster 1990, Suuronen et al 1995, Sangster et al 1996, Ingólfsson et al 2007). Among those works, mainly, the escape mortality has been observed with gadoids, particularly whiting (Merlangius merlangus) (see Sangster et al 1996, Broadhurst et al 1997, haddock (Melanogrammus aeglefinus) (see Sangster et al 1996), Atlantic cod (Gadus morhua), and saithe (Pollachius virens) (see Ingólfsson et al 2007).…”

“…Among those works, mainly, the escape mortality has been observed with gadoids, particularly whiting (Merlangius merlangus) (see Sangster et al 1996, Broadhurst et al 1997, haddock (Melanogrammus aeglefinus) (see Sangster et al 1996), Atlantic cod (Gadus morhua), and saithe (Pollachius virens) (see Ingólfsson et al 2007).…”