Lake sturgeon are Ontario’s largest and longest-lived freshwater fish. They can attain lengths up to three metres, weights in excess of 150 kilograms, and ages exceeding 100 years. Today, fish of this size are uncommon. However, lake sturgeon over two metres long and weighing more than 50 kilograms have been observed in the Moose River Basin in recent years.
Despite being named lake sturgeon, these fish are dependent on river environments. They reproduce and spend significant parts of their lives in rivers. Their bodies are shaped to move along the bottom of shallow, moving waters. Since these fish can attain a large size, they require the abundant food sources found in bigger rivers and connected lakes. Lake sturgeon generally live on river and lake bottoms and feed on aquatic insects, mollusks, crayfish, and small fish.
Lake sturgeon are migratory, moving up to 100 kilometres or more to reach a variety of seasonal habitats. In the spring, adult lake sturgeon migrate upstream to spawn (breed) in areas of fast water such as rapids, chutes, or waterfalls. They usually spawn at the same locations where they were hatched. Fast waters provide lots of oxygen, and rubble on riverbeds offers protection for incubating eggs. In the summer, fish travel long distances seeking prey in wide, shallow, and warmer parts of rivers and lakes where food is abundant. Adult fish seek out deep pools during the winter. Fish use less energy in these areas of slower water, which helps them survive the winter.
Lake sturgeon are slow-growing and take a long time to reach reproductive age. Males generally reach sexual maturity at 15 to 20 years of age and females at 20 to 25 years of age. Typically, females spawn once every 4 to 5 years. Males spawn more frequently. Observed spawning groups range in size from fewer than 50 fish to 200 fish.
The lake sturgeon’s longevity, slow growth, and relatively low reproduction rates have allowed the species to survive for millennia. These same characteristics make the lake sturgeon vulnerable to human influences.
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