Lake Chub, Couesius plumbeus

Lake chub, Couesius plumbeus.

The lake chub has a number of characteristics that differentiate it from other Canadian carp species. These include the presence of a barbel on the end of its upper jaw, 53 to 79 lateral line scales, a mouth that does not extend back as far as its eye, specific numbers of various fin rays, and the presence of hooked pharyngeal teeth. Breeding males have small tubercles that are found on various parts of their body, mostly near the head. Its body shape is slightly more elongated than that of a "typical" carp. The dorsal fin is pyramidal in shape while the caudal fin is forked, and the anal fin is approximately the same size and shape as the dorsal fin. The pelvic fin is located on the belly just in front of the dorsal fin, while the pectoral fin is inserted halfway down the gill slit.

The scientific name of this fish comes from its overall body colour, which is silvery with a leaden hue – hence the term plumbeus. Its back is olive-brown, dark green, grey, or blackish, while the flanks are a lighter shade than the back, fading into a silvery white on the belly. A dark mid-flank line runs from the snout to the tail in young fish, but fades at maturity. Breeding males have spots of orange or red on various parts of their body such as the base of the pectoral and pelvic fins as well as on the head. Lake chub only grow to a maximum length of 22 cm, placing it as a medium sized member of the carp family.

This species is found in nearly all of Canada, except the Arctic Islands, Newfoundland, P.E.I., Cape Breton, and the B.C. coast. It prefers the cooler waters of lakes, streams, and rivers. While stream populations may stay in one place all summer, lake populations move to deep water when near shore areas heat up.

Spawning takes place during the summer, once the water temperature has climbed above 10 oC. Migrations occur from lakes into rocky streams, but spawning can take place over rocky shoals or lake edges. No nest is constructed, and there is no parental care. As fertilization takes place, the eggs are scattered over the rocks where they remain until hatching. A female may shed up to 11 440 eggs over the course of a season, but only a few are released during each mating act. However, since each act takes about 1 sec, it does not take a female long to discharge all of her eggs.

Lake chub hunt by sight and consume various insects, snails, crustaceans, and small fish. In turn, they are eaten by various predatory fish and birds. This species is often used for fishing bait.