A comparative study of the diet of Loligo vulgaris (Lamarck, 1799) (Mollusca:Cephalopoda) from the south coast of Portugal and the Saharan Bank (Central-East Atlantic)

Abstract

This paper presents data on the diet of the squid, Loligo vulgaris (Lamarck, 1799) from the south coast of Portugal (Algarve) and from the Saharan Bank (Central-East Atlantic). A total of 964 squid was collected from the Algarve coast, between March 1993 and October 1994, from bottom trawling. An additional sample of 70 stomachs was obtained in the Algarve coast from the hand jigging fishery during 1991 and 1992. In the Saharan Bank, 848 squid were obtained, between June 1993 and January 1994, with bottom trawling. Stomachs with contents for trawled squid from the Algarve coast, and the Saharan Bank represented 28.1% and 40.8%, respectively. Fish was always the main component of the diet in both regions, representing 88.6% of the total weight of the prey found in the stomachs, for the Algarve coast, and 70.9% for the Saharan Bank. The occurrence percentage and the percentage in number indicated that Trachurus trachurus and fish belonging to the family Gobiidae were the most frequent fish found in the Algarve samples, while flatfish were the most common fish in the Saharan Bank samples. Loligo vulgaris was the dominant cephalopod found in the stomachs for both regions. No differences in the diet were found between males and females. The comparison between immature and mature squid showed that the importance of fish was higher in mature squid, for both regions. The squid captured from the Algarve coast by bottom trawling (at greater depths and offshore) fed primarily on fish, while those captured with hand jigging (inshore, at lower depths) contained an important percentage of crustaceans.