Rigoberto Rosas-Luis

Assessing the trophic ecology of three sympatric squid in the marine ecosystem off the Patagonian Shelf by combining stomach content and stable isotopic analyses

ABSTRACT Squid species are important components of the Southern Atlantic Ocean ecosystems, as they prey on a wide range of crustaceans, fish and cephalopods. As a result of this trophic interaction and their high abundance, they are considered reliable indicators of energy transfer and biomass in the food web. We identified Illex argentinus, Doryteuthis gahi and Onykia ingens as the most important squid species interacting on the Patagonian shelf, and used isotope analysis and stomach content identification to assess the feeding ecology and interaction of these squids in the ecosystem. Our results describe trophic interactions by direct predation of O. ingens and I. argentinus on D. gahi, and a trophic overlap of the three squid, and indicate a higher trophic level and differences in the foraging areas for mature and maturing D. gahi inferred through δ15N and δ13C concentrations. These differences were related to the segregation and different habitat of large mature D. gahi and suggest a food enrichment of C and N based on feeding sources other than those used by small maturing D. gahi and I. argentinus and O. ingens.

Food and feeding habits of Alloteuthis media in the Western Mediterranean Sea

Abstract The loliginid squid Alloteuthis media is not a commercial squid species in the Western Mediterranean Sea, and its trophic ecology is poorly known. Nevertheless, its importance as a prey resource for other squids, marine mammals and even crustaceans has been pointed out in the last decade. We analysed 124 organisms with a mantle length between 1.9 cm and 9.4 cm caught by commercial trawls in the Western Mediterranean Sea during the summer of 2013. Their diet consisted of mesopelagic and micronektonic organisms, mostly myctophid fish, and to a lesser extent crustaceans and molluscs. Based on our results, we can infer that A. media feeds on available prey suggesting active and opportunistic predatory behaviour. This agrees with information reported for other squid.