Brown trout are close relative of the Atlantic salmon, and also were brought to North American waters as exotics. These natives of Europe and western Asia were introduced into Lake Michigan waters in 1883. Brown trout have thrived in their new Great Lakes home, and have become firmly established in all of our upper Great Lakes waters.
Lake dwelling brown trout are a wary lot. They hide in shallow water that includes weed beds and rocky, boulder-strewn areas, and prefer a water temperature of 65-75 degrees. Since brown trout spawn in tributary streams in September and October, they begin to take up residence near stream outlets in spring and early summer. After ascending a particular stream, brown trout spawners choose shallow, gravelly or rocky areas. The female creates a shallow depression (redd) in the gravel, in which the spawning fish deposit the eggs and sperm. When the process is completed, the female covers the redd with gravel. The average lake run adult weighs 8 pounds, although individuals can grow to be much larger. Young browns are preyed upon by larger fish and by predatory birds such as mergansers. The diet of adult brown trout includes insects and their larvae, crustaceans, mollusks, amphibians, small rodents and other fish. They enjoy a rather long life-span, it appears, since researchers have observed them at up to 13 years of age.
Identifying characteristics: (Non-Native Fish) Two dorsal fins including one adipose fin, broad square tongue with 11-12 large teeth, light pectoral fins, square tail, 9-10 rays in the anal fin.
Brown trout is something of a misnomer for many Great Lakes members of this species, since lake-run browns are predominately silver in color. In addition, the body spots, so characteristic of their stream-dwelling cousins, are often obscured in lake-dwellers.