Feeding strategies of Polyacanthonotus rissoanus (Pisces: Notacanthidae) in the deep western Mediterranean

The feeding habits of Polyacanthonotus rissoanus, the sixth most abundant species below 1000 m on the deep slope of the Catalan Sea (western Mediterranean), were studied in the Mediterranean Sea. Samples were obtained at depths between 1000 and 2250 m. Diet was analysed for two seasons (summer and autumn) and three different bathymetric strata. The most important food items found were small epibenthic and suprabenthic crustaceans and polychaetes, and occasionally other groups such as Priapulida, Gastropoda and Foraminifera. At 1000-1425 m, the mysids were preferential prey, while in summer at all depths analysed, isopods were a dominant prey. Polychaetes have certain incidence in the diet only at 1000-1425 m, being a dominant prey in autumn. Individuals at the 1000-1425 m depth ingest larger numbers of prey of higher average sizes than those at 1425-2250 m. The scarcity of resources below 1200-1400 m resulted in diversification of diet and encouraged preying on deposited foraminiferans, molluscs or moving copepods.