The importance of cephalopods in the diet of fish on the northwest European shelf

Abstract

Cephalopods are universal to the world's oceans and prey to many fish species. On the northwest European shelf, integrated ecosystem assessments are rapidly evolving into the preferred method for holistically assessing stocks, but cephalopods appear to be an overlooked component, perhaps because their roles in ecosystems have seldom been quantified in recent years. We have analysed historical fish stomach records and revisited literature at local and regional level to determine the importance of cephalopods to the diets of 26 ecologically important finfish. We conclude that, in contrast to most other large marine ecosystems, cephalopods found in the Greater North Sea and the Celtic Seas regions appear to contribute only a small fraction to the diets of ecologically important finfish (found in the stomachs of ∼14% of specimens among some species, but generally only 1-3% in most species), though their role as predator may be important and require further investigation. Based on our findings, cephalopods may not represent a key component for integrated ecosystem assessments, though as squid populations have been shown to expand throughout the North Sea in recent years, regular monitoring is encouraged to identify the point where their inclusion into such models may be necessary.