This native "trout" is part of the salmon family Salmonidae. Like all brook trout, it belongs to the subgroup called char. Coaster brook trout and stream brook trout are genetically very similar. Because coaster brook trout spend much of their life in a large body of water, they tend to grow larger than stream-dwelling brook trout and are more silver in appearance. Wormlike markings across an olive back, magenta spots ringed by sapphire blue, red fins trimmed with white, and a squared tail distinguish this char from lake trout (Salvelinus namaycush).
Coaster brook trout live in Lake Superior and the Atlantic Ocean from Quebec to Maine. Up until around 1900, the range of the coaster brook trout included lakes Huron and Michigan. Coaster brook trout prefer coastal areas with a water depth of less than 50 feet and rocky bottom structure. Places with suitable habitat in Minnesota include Grand Portage Bay, Hat Point, and shallow areas near tributaries of Lake Superior. Coaster brook trout require stable flows and cold water in streams. Reproduction and recruitment in tributaries depend on groundwater upwelling, which is important to spawning site selection because it supplies stable temperatures and oxygenated water during egg incubation in winter. Due to the limited number of these cold-water aquifers along the North Shore, coaster brook trout were less abundant in Minnesota than elsewhere around Lake Superior.
Coaster brook trout are the only migratory (or potadromous) salmonid native to Lake Superior. After hatching in a tributary, coaster brook trout migrate to the main lake within a year or two. At about 3 years of age, they return from the main lake to tributaries to spawn. In streams they feed aggressively on aquatic and terrestrial insects as well as zooplankton. In the lake, coaster brook trout also eat small fish such as juvenile ciscoes, smelt, and sculpin.
Until the late 1800s, coaster brook trout were widely distributed in tributaries below natural barriers throughout the Lake Superior region. In the 19th century, habitat degradation and overharvest by anglers greatly diminished coaster brook trout populations in Minnesota, Wisconsin, and Michigan. Even before roads and automobiles provided greater access to the North Shore, the state's coaster brook trout population had declined, according to local fishermen. Today, development along streams and climate change are continued threats. Since 1997 Minnesota regulations have limited harvest from Lake Superior and tributaries downstream of natural barriers to one brook trout over 20 inches. As a result anglers and biologists have noticed increased numbers of coaster brook trout in recent years.
Michael A. Kallok, editorial assistant