Arctic Grayling, Thymallus arcticus

Arctic grayling, Thymallus arcticus.

The arctic grayling has a typical, elongate, trout body. Growing to a length of 38 cm, this fish has a short head and a long slender caudal peduncle. The most striking feature is its single dorsal fin, which is large and tall-rayed. Grayling also have large smooth scales and a lateral line that stretches the length of their body. The arctic grayling is attractively coloured, with a purple or blue dorsal surface, which fades to grey or blue with pink iridescence on the sides and a grey or white belly. Just in front of the pelvic fins, its sides are marked with numerous dark spots, while the dorsal, anal, adipose, and caudal fins are a dark purple-blue colour. Its long pelvic fins are dark and bear bright mauve or orange stripes.

The arctic grayling occurs in northwestern North America, from Hudson Bay through the mainland areas of Nunavut and the Northwest Territories to the Yukon and Alaska. They are also present in the northern parts of British Columbia, Alberta, Saskatchewan, and Manitoba, as well as in the Arctic regions of Asia. As arctic grayling are particularly sensitive to pollution, populations in the Great Lakes region have become extinct. The arctic grayling prefers the clear water of large cold rivers and lakes. Fish are generally found in schools, often in association with other coldwater fishes such as salmon, lake trout, rainbow trout, and whitefish.

When ice first breaks up, usually from April to June, arctic grayling migrate to small streams, preferably those with gravelly or rocky bottoms, to spawn. During the breeding season, males become aggressive and territorial. When confronted by an intruder, they exhibit threat displays: they raise their dorsal fin, extend their pelvic fins, and vibrate their bodies. Not only is their long dorsal fin used in threat displays, but it is important during spawning; males use the fin as a clasping organ to hold the female! To mate, the male and female vibrate side by side, releasing eggs and milt into the water. There is no nest construction; instead, the eggs are covered by material stirred up from the stream bottom during the vibrations of the mating pair. Adults provide no parental care, but return to their home lake or river immediately after spawning. The eggs hatch in just two weeks, releasing small larvae that are nourished by their yolk sac for another week. Although sexual maturity is reached by 4 years of age, the majority of spawners are 6 to 9 years old.

Young arctic grayling feed mostly on zooplankton, but as they grow, they tackle the larval stages of mayflies, midges, and caddisflies. Adults feed on aquatic and terrestrial insects, fish eggs, small fish, and crustaceans, while falling prey to eagles, osprey, gulls, minks, and otters. Because the grayling is both palatable and aesthetically pleasing, it is much sought after by recreational anglers.