Trophic relationships and food consumption of slope dwelling macrourids from the bathyal Ionian Sea (eastern Mediterranean)

Abstract

Daily and seasonal changes in dietary habits, resource partitioning and daily food consumption of Coelorhynchus coelorhynchus, Hymenocephalus italicus and Nezumia sclerorhynchus, the three dominant macrourids coexisting at mid-slope depths (between 473 and 603 m) in the eastern Ionian Sea, were analysed. The three species showed very diverse diets, based mainly on suprabenthic prey and infauna. Day-night changes in the diet and feeding intensity were more apparent in H. italicus and N. sclerorhynchus, preying mainly on mobile prey (suprabenthos), than for C. coelorhynchus that preyed largely on infauna. Dietary overlap was very low among species. The highest daily ration (DR) obtained for N. sclerorhynchus (in April) coincided with maximum concentration of its preferred prey (i.e. Boreomysis arctica). H. italicus, displaying a more pelagic diet than N. sclerorhynchus, showed higher DR (between 1.47-1.51%wetW and 0.47-0.71%wetW, respectively) probably due to higher metabolic activity because it may swim up in the water column to eat. C. coelorhynchus, having the most benthic diet, showed the highest DR (between 2.92 and 2.53%wetW). This rather unexpected high DR would be attributable to a continuous feeding on more uniformly distributed prey (benthos) and to a high rooting activity on the sediment in search of infauna. The influence of the type of resources exploited in the overall trends obtained in the diet of macrourids is discussed and compared with those of other deep-sea species. As a general conclusion, results suggest that food consumption of bathyal fish are probably influenced by or coupled with the type of resources exploited. © Springer-Verlag 2005