Greenland Halibut Depth Variations of Catch-per-unit Effort, Length Composition, Mature Proportions and Associated By-catches in Divisions 3LMNO

Abstract

In this paper we present a review of the geographic and bathimetric patterns of occurrence of the Greenland halibut catches in NAFO Divisions 3LMNO and their incidence on the catch of other stocks, namely cod, American plaice and yellowtail and witch flounders. The Greenland halibut mature proportions at depth in both the commercial catches and the spring Spanish 3NO survey indices are also presented. According to the results of the Spanish fleet, the Greenland halibut fishery does not overlap significantly with either American plaice, yellowtail flounder, skate or cod. By-catches of witch flounder in the Greenland halibut fishery have been very small, at least in 1999. The CPUE analysis indicate that Greenland halibut is best caught in the deepest strata, with catch rates comparatively poor at depths less than 600 m. Besides a sharp change in catchability is observed between 500 – 600 m. The proportion of mature fish in the catches increases with depth attaining a maximum between 1200 – 1600 m. The survey results indicate that most part of the SSB is found at depths beyond 800 m.