Diet of the horned octopus Eledone cirrhosa in Atlantic Iberian waters: ontogenetic and environmental factors affecting prey ingestion

Growing concern over sustainability of some fisheries has led to a shift in the focus of fisheries management, from a single-target species towards an ecosystem-based management. This process involves identification a suite of indicators, among which ontogenetic and environmental factors affecting prey ingestion should be considered. The present study combines morphological and molecular analysis of stomach contents and Multinomial Logistic Regression (MLR) to understand the dietary regime and factors affecting it in Eledone cirrhosa inhabiting Atlantic Iberian waters. Specimens were collected monthly from commercial bottom trawl multispecies fisheries between February 2009 and February 2011 in three fishing grounds (North Galicia, West Galicia and North Portugal). Based on stomach analysis, E. cirrhosa ingested mainly crustaceans, followed by teleost fish, echinoderms, molluscs and polychaetes. Molecular analysis of 14 stomach contents confirmed the visual identification of prey items as well as cannibalistic events. Statistical tests found that sex and body weight did not significantly affect prey selection, while season, fishing ground and maturity stage of the animals had a significantly effect on the probability of selecting a particular prey. The ecological implications of MLR modelling results are discussed.