Lake whitefish average 457 mm in length. They are covered in scales that range from pea green or almost brown on their backs to silvery white on their stomachs. The sides have a bluish hue and the fins are nearly transparent. There are two dorsal fins, including an adipose (fatty) fin which is sometimes larger in males. The nose is blunt, with a small mouth. Lake whitefish have long, streamlined bodies, as do most members of the salmon family.
Lake whitefish are found mainly in large, cold, freshwater lakes and their tributaries. They make small, seasonal migrations between different water depths. They are found in deeper water in summer and winter, returning to shallower water in spring and again in fall or early winter to spawn over rocky shoals and reefs along lakeshores. They can be found at water depths from 5 to 110 meters or deeper, although ranges of 15 to 37 meters are more typical.
Lake whitefish spawn in shallow water. Spawning occurs in fall and early winter and the eggs are broadcast over the shoals, where they settle to the bottom. Eggs hatch in March or early April, taking about 133 days to hatch in waters averaging 1.7 degrees Celsius.
Lake whitefish spawn in large groups over shallow water shoals in fall and early winter. Females repeatedly rise to the water's surface while releasing eggs. They are accompanied by either one or two males who fertilize the eggs.
Lake whitefish spawn in the fall or early winter and eggs hatch in the early spring. Females release thousands of eggs when they spawn, with larger females having more eggs. One female that weighed 907 g had 25,000 eggs and another female that weighed 5.9 kg had 130,000 eggs.
Lake whitefish males and females do not care for their young after the eggs have been fertilized.
Most mortality of lake whitefish occurs at the egg and larval stages. Only about 13% of eggs survive to become larvae and larvae are heavily preyed on by larger fish. The maximum recorded age of a lake whitefish was 50 years old, although maximum ages of 25 years are more typical. (Becker, 1983; Luna, 2008)
Lake whitefish are fairly sedentary in the Great Lakes, although they make seasonal movements between deep and shallow water. They typically make 4 short, seasonal migrations: from deep to shallow water in the spring, back to deep water in summer as water temperatures rise, to spawning areas in shallow water in the fall and early winter, and back to deep water in the winter. Lake whitefish are social and are always found in schools. (Luna, 2008; Michigan Department of Natural Resources, 2008)
Total distances traveled during migrations have been recorded at 8 to 242 km, but the vast majority of fish do not travel more than 40 km. Schools of lake whitefish seem to remain fairly local in their movements. (Becker, 1983)
Like most fish, lake whitefish have a lateral line system that allows them to detect water movement. They also have good vision and sense of smell. In mating, tactile cues may be important as males and females coordinate to release eggs and sperm.
Lake whitefish have small mouths and eat mainly small prey, including aquatic insects (fly larvae caddisfly larvae, midge larvae, mayfly nymphs, and water boatmen), amphipods, snails and clams, and fish eggs and fry. They have been recorded eating small alewives and sculpin. They forage mainly on or near the lake bottom.
Lake whitefish eggs are eaten by a host of other fish, including yellow perch, ciscoes, and other whitefish. Juvenile lake whitefish are also eaten by a host of larger, predatory fish, including lake trout, northern pike, burbot, and walleye. Adult lake whitefish are largely preyed on by humans. (Michigan Department of Natural Resources, 2008)
Lake whitefish are both important prey, as eggs and young, for many other fish species, and important predators of aquatic insects, mollusks, and crustaceans. Lake whitefish are parasitized by introduced sea lampreys. (Michigan Department of Natural Resources, 2008)
There are no adverse effects of lake whitefish on humans.
Lake whitefish have long formed the basis for important subsistence and commercial fisheries. They are not commonly sought as gamefish, although more anglers are beginning to seek them out. They are difficult to catch with hooks because of the deep water they sometimes inhabit and small mouths. Lake whitefish flesh is considered delicate and delicious and the roe is valued for caviar. (Luna, 2008; Michigan Department of Natural Resources, 2008)
Overfishing and environmental degradation caused a near collapse of lake whitefish fisheries in the Great Lakes during the early part of the 20th century. Water quality improvement and fishery management has improved populations since then, although local populations remain threatened and the health of lake whitefish stocks has not fully recovered under continuing commercial fishing pressure. (Becker, 1983; Michigan Department of Natural Resources, 2008)
Tanya Dewey (author), Animal Diversity Web.
Becker, G. 1983. Fishes of Wisconsin. Madison, Wisconsin: The University of Wisconsin Press.
Luna, S. 2008. "Coregonus clupeaformis" (On-line). fishbase.org. Accessed December 11, 2008 at http://www.fishbase.org/Summary/SpeciesSummary.php?id=234.
Michigan Department of Natural Resources, 2008. "Lake Whitefish, Coregonus clupeaformis" (On-line). Michigan Department of Natural Resources, Fish Identification. Accessed December 11, 2008 at ttp://www.michigan.gov/dnr/0,1607,7-153-10364_18958-45680--,00.html.