Lake Sturgeon, Acipenser fulvescens

Growing to a length of almost 3 m and a weight of 140 kg, the lake sturgeon is the largest freshwater fish in North America. It is very hard to confuse this fish with any other, because of its prehistoric appearance and huge size! Like other sturgeons, it has a long armoured body, a large tail, a long pointed snout, heavyset fins, and long chin barbels. It can be distinguished from other sturgeon species by the single large plate between the caudal and anal fins, as well by the number of rays in the various fins and the numbers of plates along the side of the body. Its back and upper sides are dark brown or olive-grey, fading to a grey or white belly, and its fins are dark brown.

The lake sturgeon prefers shallow areas of lakes and large rivers at depths from 5–9 m. Although it is primarily a freshwater species, it enters brackish water in the Arctic drainages of James Bay. Elsewhere, the species occurs throughout Ontario, Manitoba, and south through the USA to Alabama.

Although the lake sturgeon is very large, it is not a predator of other fish, but instead hunts for a wide variety of animal and plant material in the bottom substrate. Sediment is inhaled through the extensible mouth and then filtered through the gills. The barbels that hang from the snout are used to detect food as the sturgeon swims slowly along the bottom. Crayfish and other crustaceans, clams, snails, aquatic insects, fish eggs, and algae are consumed. Predators are rare due the sturgeon's large size; however, lamprey are known to parasitize them. Sturgeon can sometimes be seen jumping out of the water in an effort to rid themselves of a clinging lamprey.

Spawning occurs from April to June when the water temperatures have reached 12°C to 18°C in running water or at lake edges with plenty of wave action. The lake sturgeon is generally sedentary, but spawning migrations of up to 400 km sometimes occur, especially for lake dwelling populations. Males usually arrive first at the spawning grounds, followed soon after by the larger females. Mating takes place in groups consisting of one female and one to two males, and involves splashing, vibrating, and leaping. The black eggs measure 3.5 mm in diameter and are shed over the course of a few days. They adhere to rocks in the spawning grounds. Lake sturgeon may live as long as 154 years, but age determinations are difficult in older individuals. The average maximum age for females is 96 years and 55 years for males.

This species has been exploited for a number of human uses. The eggs are valued as caviar, the skin is made into leather, and the swim bladder is used to make a form of gelatin. Unfortunately, damming, overfishing, and pollution have reduced populations considerably. The elastics used by Canada Post to bind mail, when not disposed of properly, can end up in waterways and get caught on the snout of lake sturgeons grubbing in the mud for food. The elastic bands become embedded in the sturgeon's head and interfere with feeding and can leave the fish open to infections.