Bull trout are members of the salmon family and can grow to more than 20 pounds (9kg) in lake environments. Bull trout that live in streams rarely exceed 4 pounds (2kg). They reach sexual maturity at between four and seven years of age, and they can live up to 12 years.
Bull trout spawn in the fall after temperatures drop below 48 Fahrenheit (8 Celsius). Their eggs require a long incubation period - about four to five months, hatching in late winter or early spring. Some bull trout may live near areas where they were hatched, and others migrate from streams to lakes.
These fish have small, pale yellow to crimson spots on a darker background, which ranges from olive green to brown, fading to white on the belly. Their diet consists of aquatic insects, but they shift to preying on other fish as they grow larger.
Bull trout are native to the Yellowstone to Yukon region and are most commonly found in the high mountains of western North America. Bull trout are sensitive to increased water temperature, poor water quality, and low flow conditions.
Photo: Corey Fisher