Diet of the squid Loligo forbesi Steenstrup (Cephalopoda: Loliginidae) in Irish waters

Abstract

Stomach contents of Loligo forbesi obtained from commercial landings and research cruises in Irish waters and the Irish Sea were examined. A total of 62.3% of stomachs were empty. Fish remains occurred in 73.7% of all full or partially full stomachs, with crustaceans and cephalopods occurring in 26.4% and 7.5% respectively, L. forbesi was found to consume a wide range of fish and crustacean prey. Sagittal otoliths were used to identify fish species, and vertebrate to identify families. The most frequent species by per cent occurrence sprat ( Sprattus sprattus ), poor cod ( Trisopterus minutus ), Norway pout ( T. esmarkii ), and transparent goby ( Aphia minuta ). Crustaceans were the main prey item is squid of less than 100 mm mantle length, together with small clupeids and gobies. the predominant prey of medium-sized squid (100–220 mm) was found to be gadoid and clupeid fish, while gadoids and other cephalopods were the main prey of larger squid (>220 mm). Seasonal differences in the diet were apparent but were shown to be influenced by seasonal changes in squid size.