MEPS 354:277-287 (2008)  -  DOI: https://doi.org/10.3354/meps07246

ABSTRACT: Investigations of trophic interactions between marine mammals and marine resources typically use trophic models that are based on food composition, energy content of the prey and energy requirements of the predators. Although the diets are known to vary intraspecifically according to year, season, sex and age, this variation is rarely taken into account in published models. The aim of the present study was to assess the diet of the short-beaked common dolphin Delphinus delphis in the Bay of Biscay (France), examine intraspecific dietary variation and explore its effects on calculated daily food intake. Stomach contents were analysed from 71 common dolphins stranded along the French coast between 1999 and 2002. The composition of the fresh fraction of the diet was quantified by occurrence, relative abundance, reconstructed mass and prey size distributions for all prey taxa. Overall, the most important prey species were sardine, anchovy, sprat and horse mackerel, which represented 44.9, 22.6, 8.0 and 5.0% by mass of the fresh diet, respectively. The diet composition displayed significant variation in relation to season and sex/maturity status, in terms of both prey species composition and prey size distributions. Temporal variation in diet composition was interpreted in relation to prey availability in the Bay of Biscay. Because different prey types have different energetic values, changes in diet composition could lead to changes in the estimated total biomass needed to fulfil energetic requirements. In spite of the main prey species varying extensively, estimated daily food intakes changed relatively little because all diets included a high proportion of fat fish (73 to 93% by mass).

KEY WORDS: Diet · Delphinus delphis · Common dolphin · Energy requirements · Prey availability · Stomach content analysis