Diets of squid Loligo forbesi and Loligo vulgaris in the northeast Atlantic

Abstract

Diets of the loliginid squid Loligo forbesi and Loligo vulgaris were investigated by stomach contents sampling during 1990–1993. Monthly samples of Loligo forbesi were collected at Aberdeen and additional samples were obtained from the Irish Sea, Faroe, the English Channel, Vigo, Lisbon and the Azores. Samples of Loligo vulgaris were obtained from Vigo, Barcelona, Lisbon and Faro. Loligo forbesi feeds primarily on fishes, crustaceans and cephalopods. In Scottish waters, Gadidae (mainly Merlangius merlangus and Trisopterus sp.), Ammodytidae and Clupeidae were the most frequently identified prey. The relative importance of fish was slightly higher, and that of crustaceans lower, in the diet of larger squid. Gadidae and Clupeidae were more prominent in the winter diet, with sandeels being taken more frequently in the summer. The same prey taxa were important in the diet of Loligo forbesi across all areas. Fishes occurred in more than 80% of non-empty stomachs except for the Lisbon sample, in which crustaceans were the most frequently identified prey taxon. The species composition of the diet varied between areas. Thus, scad Trachurus picturatus was the most important prey in the Azores. The broad composition of the diet in Loligo vulgaris was similar, although crustaceans were apparently less important, but there were differences in species eaten between areas, and between the two Loligo species. Samples of the ommastrephid squid Todaropsis eblanae taken at Aberdeen indicated that this species was also primarily piscivorous, taking Gadidae and Clupeidae.