Food resource partitioning between three sympatric fish species in Porsangerfjord, Norway

Abstract

Understanding predator–prey relationships and resource overlap between sympatric species is fundamental for enhanced scientific knowledge and management. This study compared the trophic ecology of three small demersal fishes (Artediellus atlanticus, Myoxocephalus scorpius, and Leptagonus decagonus) using stomach data and stable isotope analyses. All fish were sampled during 2009–2011 from the inner basin of Porsangerfjord (70°N, 25°E) in northern Norway. The dominant prey found in A. atlanticus was polychaetes, while M. scorpius had fed on juvenile fishes and decapods, and L. decagonus had mainly consumed copepods. The trophic positions of the fishes overlapped extensively (A. atlanticus: trophic level (TL) 3.4–4.2; M. scorpius: TL 3.6–4.3; L. decagonus: TL 3.7–4.6). Although the nutritional origin (δ13C) of the prey varied among the fishes, A. atlanticus and M. scorpius were associated with benthic prey (δ13C −18.64 to −17.28 and δ13C −18.67 to −17.04, respectively), whereas L. decagonus was associated with pelagic prey (δ13C −19.95 to −18.74). The combined results of the stomach data and stable isotope analyses further suggested that M. scorpius had a dietary preference for benthic–pelagic prey. Thus, the fish diets were considered to be species specific, and the study indicated that the three species utilize different prey groups within the food web of the Porsangerfjord ecosystem.