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Niche partitioning among demersal marine fishes at the southern tip of South America

C. D. Alvarez*, A. R. Giussi, F. Botto

*Corresponding author:

ABSTRACT: Niche differentiation is the way species coexist and avoid competition. In marine food webs, large demersal fish often couple different trophic pathways, and can be targets of valuable fisheries. This is the case of the long tail hake Macruronus magellanicus, the Patagonian toothfish Dissostichus eleginoides, the southern blue whiting Micromesistius australis and the southern hake Merluccius australis, which coexist in the southernmost region of the Southwestern Atlantic Ocean. In this study, C and N stable isotope and stomach content analyses were used to evaluate possible niche partitioning among these four species. Long tail hake and southern blue whiting mainly eat crustaceans, with great overlap in their diet spectra, but they differentiate in their spatial distribution. The southern hake and the Patagonian toothfish mainly feed on fish, including the other two species, and exploit prey from broad spatial area. These results suggest a spatial compartmentation of the food web in the lower levels, with demersal fish in the higher levels linking distant compartments. Therefore, results of this study show similarities and differences among these four demersal fish species, in the trophic and spatial dimension of their niche, suggesting niche differentiation and probably different roles in the food web.