Comparative feeding ecology of the sympatric cod fishes Arctogadus glacialis and Boreogadus saida in North East Greenland evaluated from diet and stable isotope analyses

Abstract

The fish fauna was investigated in autumn 2003 during the TUNU-I Expedition to NE Greenland fjords. Two gadoids Arctogadus glacialis and Boreogadus saida were abundant in many trawl hauls. In this study, the stomach contents and the stable isotope composition were determined in 60 Arctogadus glacialis and 50 Boreogadus saida from Tyrolerfjord and Dove Bugt. The diets were examined by Stomach Contents Analysis (SCA) and compared with chi-square test and Schoener index. The diets were similar containing the same prey species, mostly crustaceans (copepods, mysids and amphipods). Significant differences were found, mainly in the proportions of two crustaceans, the mysid Mysis oculata and the copepod Metridia longa. Fish was found in the stomachs of large Arctogadus glacialis. The stable isotope composition was analyzed with Stable Isotope Analysis (SIA). Differences were discovered between species and fjords. Arctogadus glacialis had δ13C mean of -20.81 and -21.33‰, δ15N mean of 14.92 and 14.21‰, in Tyrolerfjord and Dove Bugt, respectively. Boreogadus saida had δ13C mean of -21.25 and -21.52‰, δ15N mean of 13.64 and 14.47‰ in the respective fjords. Trophic levels of the species were inferred from mean δ15N-values. The mean δ13C and δ15N values for the predators corresponded well with those of the prey species from the literature, with an enrichment value of 3.8‰ for δ15N. This is the first study that examines the isotope signature and trophical position of Arctogadus glacialis.