First records of Atlantic mackerel (Scomber scombrus) from the Svalbard archipelago, Norway, with possible explanations for the extension of its distribution
Atlantic mackerel Scomber scombrus were recorded in Isfjorden, Svalbard (78@15' N, 15@11' E) in late September 2013. This record is the northernmost known occurrence of mackerel in the Arctic and represents a possible northward expansion (of ca. 5@ latitude) of its distributional range. The examined specimens of mackerel were between 7 and 11 years old, with a mean size of 39 cm and a mean weight of 0.5 kg. Examination of stomach contents indicated that the mackerel were feeding mainly on juvenile herring Clupea harengus The occurrence of mackerel in the Arctic is discussed in relation to the recent increase in mackerel population size in the North Atlantic and the expansion of other North Atlantic fishes into the Svalbard region during the last decade. Using a decadal record of water temperature, we conclude that the occurrence of Atlantic mackerel in Svalbard waters is a result of a continued warming of the ocean in the region and that it follows a general trend of species' extending their distributional ranges northward into the Arctic.