Sampling herring in the Norwegian Sea by pelagic trawl

Abstract

When the stock of Norwegian spring-spawning herring is distributed in the Norwegian Sea in summertime, pelagic trawl sampling may be rather challenging because of substantial variation in vertical distribution (from surface and down to 400 m depth), and avoidance of vessel and trawl gear. In this paper the operation and performance of the «Åkratrål» during pelagic trawl sampling of herring by R/V «G.O. Sars» on cruises in the Norwegian Sea 1996 - 1997 are described. The sampling results with regard to capture success, catch size and geograpically segregated length distributions are presented. The implications of the sampling results on the reliability of the acoustic estimate of stock size are discussed.