Feeding habits of Alepocephalus rostratus (Pisces: Alepocephalidae) in the western Mediterranean Sea

The present study examines the feeding habits of Alepocephalus rostratus, the only species of the family Alepocephalidae in the Mediterranean Sea and the second most important fish species, in terms of biomass, inhabiting the deep slope of the Catalan Sea. Samples were obtained at depths between 1000-2250 m. Diet was analysed for two different size-classes (immature and mature specimens) at three different bathymetric strata during two different seasons. The feeding habits of A. rostratus included a narrow range of mobile macroplanktonic organisms (e.g. Pyrosoma atlanticum and Chelophyes appendiculata) and some material of benthic origin. Pyrosoma atlanticum was the preferred prey item in spring at 1000-1425 m, being very scarce in summer at the same depth as a consequence of its scarcity in the environment during this season. There were some ontogenic differences in the diet of A. rostratus at 1425-2250 m. Adults ingested more and larger prey than juvenile specimens. The scarcity of resources below 1200-1400 m fostered a more diversified diet, as well as passive predation of sedimented material.