Performance and Biological Implications of a Multi-gear Fishery for Greenland Halibut (Reinhardtius hippoglossoides)

Abstract

Simultaneous full-scale fishing operations using bottom trawl, gillnet and longline for Greenland halibut (Reinhardtius hippoglossoides, Walbaum) were performed in the Barents Sea (ICES Divisions IIa and IIb) for two weeks in October 1992. The mesh size of the trawl codend was 135 mm, and that of the gillnets 220 mm. Additionally, seven gillnet fleets of 180 mm mesh size were set for selectivity comparison. The catch rates and the length distributions of the Greenland halibut in the catches taken by trawl, longline and gillnet were different. Gillnets almost exclusively caught fish between 60 and 70 cm, mostly mature females (about 90%). The size distribution taken by longline was wider than that taken by gillnet. Two thirds of the longline catches were females, and the proportion of immature individuals was larger (14–30%) than in the gillnet catches. The trawls, however, caught large amounts of fish between 40 and 60 cm, consisting of almost equal amounts of males and females, and 30–40% immature fish. Gear-specific selection properties were the main reasons for the observed differences. Yield-per-recruit and spawning-stock-biomass-per-recruit analyses showed that fixed gears captured proportionally fewer immature fish, and thus indicated they would provide greater spawning biomass and yield-per-recruit than would trawl gear, for an equivalent reference fishing mortality rate.