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.

RESPONSIBLE EDITOR:

• Haakon Hop

KEYWORDS:

• Doryteuthis gahi
• Illex argentinus
• isotope analysis
• Onykia ingens
• South Atlantic Ocean
• trophic ecology

Acknowledgements

We are grateful to Dr Isabel Palomera for her support during the design and preparation of the present study. We would also like to express our gratitude to Angelo Sanna, Javier Torres Rodríguez and Roberto Mendoza Bruzzone, for their support during sample collection in the framework of the ATLANTIS project funded by the Spanish Oceanographic Institute (IEO). Sarah Young kindly revised the English. Three anonymous reviewers provided useful comments that improved this paper.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

JN was supported by the Andalucía Talent Hub Programme launched by the Andalusian Knowledge Agency, co-funded by the European Union's Seventh Framework Programme, Marie Skłodowska-Curie actions and the Ministry of Economy, Innovation, Science and Employment of the Junta de Andalucía, Spain. This study represents a contribution to the project ECOTRANS (CTM2011-26333, Ministerio de Economía y Competitividad, Spain).