Feeding habits in two sympatric species of Notothenioidei, Patagonotothen cornucola and Harpagifer bispinis, in the Chilean Patagonian channels and fjords

Abstract

Diet compositions of Patagonotothen cornucola and Harpagifer bispinis were studied from two localities, one with continental influence in a wind-protected area (Puerto Riquelme) and another with oceanic influence in a wind-exposed area (Puerto Williams). The dietary analysis performed showed intra-specific differences among contrasting intertidal areas, with greater richness and diversity of prey types in fish from Puerto Riquelme than in Puerto Williams. Gammarid amphipods and Tanaidae dominated the diet of P. cornucola and H. bispinis in Puerto Riquelme, whereas the diet of both fish species in Puerto Williams was characterized by the crustacean isopod Exosphaeroma gigas and gammarids. The dietary overlap was quantified using two similarity indexes (Sorensen and Morisita-Horn), and the results obtained revealed a high diet overlap among the species in each locality. Diet composition did not show significant difference between sexes in both species, while P. cornucola from Puerto Riquelme presented significant differences in fish size in the diet, supporting the existence of some food partitioning. Dissolved oxygen and salinity were important factors in the diet variability of P. cornucola and H. bispinis, since both species showed greater richness and diversity of prey types in intertidal areas with higher dissolved oxygen and lower salinity levels (Puerto Riquelme). In conclusion, the dietary patterns of these two sympatric rocky intertidal species in the Patagonian channels and fjords appear to be regulated by the different environmental conditions that influence the availability and abundance of potential prey in the diet.