Capelin, Mallotus villosus
In June and July every year, the beaches and shorelines of Newfoundland and Hudson Bay are invaded by spawning capelin. This mass migration towards the beaches also attracts the attention of predators; whales, seabirds and humans prey heavily upon spawning capelin. Despite these heavy losses, capelin are still one of the most important forage fish in the Arctic and the Northwest Atlantic.
The capelin is a long, slender fish that rarely exceeds a length of 20 cm. It has a pointed head and a long snout with a terminal mouth. Two dorsal fins, one soft rayed, and one adipose fin occur in front of the deeply forked caudal fin. During the spawning season, male capelin have an angular appearance because of two rows of enlarged scales running the length of their body. Males have larger fins and are generally larger than females at sexual maturity.
One of the most interesting aspects of capelin is their method of spawning. During the months from April to July, at night or on cloudy days, and in water temperatures between 5.5°C and 8.5°C, males gather in large schools in shallow waters. The fish are rather choosy about spawning conditions, and their preferences extend to the size of sand on their spawning beaches, with grains between 1 and 15 mm favoured. Beaches with these conditions are visited year after year, and are known as capelin beaches. When females arrive, a pair or triplet – one female and two males – will swim with a wave up onto the beach, jumping through the air in an attempt to get as far up as possible. With a male at her side, the female capelin releases her eggs, which are subsequently fertilized. The process takes about 5 seconds, following which both sexes make their way back into the water with flapping movements of their bodies. Further wave action buries the eggs in up to 15 or more cm of sand, where they are safe from predators and weather. Beach spawning is dangerous business, and a large proportion of capelin perish in the process, particularly males. Some are stranded on land, and, despite the ability of these hardy fish to withstand prolonged periods out of the water, do not make it back to the sea. Many are eaten by predators, including humans, quick to take advantage of the large numbers of beached fish. Hatching of the reddish coloured eggs takes place in 1–4 weeks, and the larvae stay in the gravel until wave action washes them into the water.
Capelin occur in both the north Atlantic and Pacific and thus have a circumpolar distribution. In the Pacific they are found from Cape Barrow, Alaska through the Bering Sea and down the coast to Juan de Fuca Strait. In the North Atlantic they range from Hudson Bay to Nova Scotia and sometimes to Cape Cod.