Cephalopod consumption by trawl caught fish in Scottish and English Channel waters

Although there have been numerous studies on diets of fish from European wa ters, they are often of limited use for estimating the impact of fish preda tion on cephalopod resources. This is due to either the origin of the fish sampled, e.g. from areas with a relatively low cephalopod abundance, or to the method of prey identification: cephalopods are rarely identified to spe cies. This paper presents a summary of recent sampling of the cephalopod sp ecies appearing in the diet of commercially important fish species in UK wa ters. Samples of demersal fish from around Scotland and from the English Ch annel were collected opportunistically during: research trawl surveys and f rom commercial trawlers in different seasons. For all fish species examined , incidence of cephalopods in the stomachs was low, with fish and crustacea n prey dominating stomach contents. Most of the cephalopods found were spec ies with little or no commercial value and small adult body size, such as t he small loliginid squid Alloteuthis spp. and bobtail squid (Sepiolidae). O nly during December 1998 were some commercially valuable squid (Loligo spp. ) observed in fish stomachs, although in relatively small quantities and co mprising mainly of pre recruit individuals. It is reasonable to suggest tha t most commercially fished teleosts have little direct impact on post-recru its of commercially important cephalopod stocks, although their impact on r ecruitment may be significant. The stomach contents data are used to provid e a rough estimate of cephalopod consumption by cod populations in the stud y area and the use of such data to estimate natural mortality is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.