Diets of deep-sea macrourid fishes in the western Mediterranean

Abstract

The feeding habits of the 4 most abundant macrourids that occur on the deep slope of the Catalan Sea (western Mediterranean) were examined for the first time for the Mediterranean at depths between 1000 and 2250 m. Diets of Chalinura mediterranea, Coryphaenoides guentheri, Coelorhynchus labiatus and Trachyrhynchus trachyrhynchus were analysed for 2 seasons (summer and autumn) and/or 3 different bathymetric strata. Coryphaenoides guentheri was the most euryphagous and T. trachyrhynchus the least. Chalinura mediterranea, Coelorhynchus labiatus and T. trachyrhynchus has a benthopelagic diet, whilst Coryphaenoides guentheri has a benthic diet. Coelorhynchus labiatus has a slight preference for bathybenthic prey (polychaetes, gammaridean amphipods) whereas Chalinura mediterranea and T. trachyrhynchus display a preference for bathypelagic prey (calanoid copepods, mysids). Chalinura mediterranea and Coryphaenoides guentheri have bathymetric differences in diet marked by the capture of different prey-items and also by a greater vacuity, a greater consumption of prey and a greater diversity at 1800 to 2250 m. A greater diversity in the diet is found in the Mediterranean populations of Chalinura mediterranea, Coryphaenoides guentheri and Coelorhynchus labiatus than in the Atlantic populations; this is probably an adaptation to the faunal paucity of the Mediterranean deep sea. General affinities among the diets of all macrourids are also analysed. The apparent coincidence between the diets of Chalinura mediterranea and T. trachyrhynchus could explain the bathymetric segregation of their respectives niches. Coelorhynchus labiatus, whose habitat width lies within those of the other 3 macrourids, has a dietary overlap intermediate to those of the other 3 macrourids. Ecological separation is maintained by a combination of differential depth distribution and feeding habits.