Feeding ecology of capelin (Mallotus villosus Muller) in West Greenland waters

Capelin (Mallotus villosus Muller) is a key pelagic mediator of energy from lower to higher trophic levels in arctic waters. This is also the case in Greenland waters, but little is known of its feeding behaviour in this region. By analysing stable nitrogen isotopes and stomach content of capelin collected along 1500 km of the Greenland west coast, this study aims to provide knowledge on capelin feeding ecology and the role that diet composition and biomass may have in generating the observed latitudinal growth differences in Greenland capelin. In total, 572 stomachs were sampled. The most dominant prey by wet weight was euphausiids (61 %) followed by amphipods (18 %) and copepods (10 %). The most common species were Thysanoessa raschii, Themisto libulla, Calanus finmarchicus and Calanus hyperboreus. Copepods dominated in smaller capelin but were replaced by euphausiids in larger fish. A similar prey shift towards euphausiids along with an increase in prey weight (relative and absolute) was seen with increasing latitude. The spatial variation in feeding pattern was supported by stable nitrogen analyses. The mean delta N-15 values of capelin muscle tissue for the south (60-64A degrees N) and north (68-72A degrees N) were 9.54 aEuro degrees +/- A 0.72 and 12.47 aEuro degrees +/- A 0.38 (mean +/- A SD), respectively. However, when differences in isotopic baseline values (C. finmarchicus delta N-15, 2.47 aEuro degrees) in the two areas were taken into account, the isotope values suggest that capelin in the northern areas fed on a slightly higher trophic level higher than in the south, as would be expected with increasing importance of euphausiids. These significant feeding differences along the Greenland west coast are likely impacting capelin growth and condition as they show parallel trends along the same gradient.