Trophic habits of two ommastrephid squids, Illex coindetii and Todarodes sagittatus in the Western Mediterranean Sea.

Abstract

Illex coindetii and Todarodes sagittatus squid cached by commercial trawls in the Western Mediterranean Sea during 2010-2012 were used to describe and compare their feeding behavior. A total of 121 I. coindentii and 161 T. sagittatus stomach contents were analyzed. Crustacean and Fish were the main prey items in both species and mollusks were observed. Pasiphaeidae and Amphipoda crustaceans were identified in 33.88 and 9.09 % of I. coindetii and 18 and 25 % of T. sagittatus and 18 different otoliths were recovered for 59.5% of I. coindetii while 22 in 54.27% T. sagittatus, Paralepididae and Myctophidae were observed as fish prey items but the most prevalent item for both species in frequency and abundance was Paralepididae. According to the Importance Relative Index the main prey items for both species were the crustacean Pasiphaea multidentata, and the amphipod Anchylomera blosseville which were present in the feeding behavior of both squid species. I. coindetii showed a preference for Lestidiops sp. while Arctozenus risso was preferred by T. sagittatus, and the same in crustaceans where I. cooindetii diet was integrated by P. multidentata, A. blossevillei, and Pasiphaea sivado while in T. sagittatus was integrated by P. multidentata, Phronima sedentaria, A. blossevillei, Decapoda, Phrosina semilunata and others. Teuthida was the main prey item group in mollusks and it appears that the cannibalism is not a common tendency in both species, however other squid species were present and T. sagittatus fed on Histeoteuthis reversa, Ancistroteuthis linchtensteinii and I. coindetii while I. coindetii on Todaropsis eblanae, T. sagittatus, and Loligo forvesii. Both predators fed substantially on crustaceans and fish but T. sagittatus fed on a wider range of prey items (21 crustacean and 22 fish species) than I. coindetii (8 crustacean and 18 fish), suggesting that T. sagittatus is a more generalized predator than I. coindetii and the competition for food resources appears low between both species as result of a different diet composition