Brook Trout

Characteristics

Brook Trout are easily recognized and distinguished from other trout by vivid white lines on the front or leading edge of the lower fins, and the top portion or back is covered with light wormy streaks or mottlings on a darker background called vermiculations. The dorsal fin has ten rays and is also strongly mottled. The vomer is trough-shaped, with the teeth restricted to the front portion. Brook trout feel soft to the touch because of the very small scales that cover the whole body. About 230 scales are along the lateral line, and they are more deeply embedded than other trout in the genus Salmo.

Distribution

Native to Iowa; originally abundant in most spring-fed streams of northeastern Iowa, although some fishery investigators believe they were restricted to the Upper Iowa River drainage. Confirmation of the original distribution is difficult because early explorers referred only to the fish as "mountain" or "stream" trout, without looking for identifying characteristics. Natural reproduction of Brook Trout is presently limited to only a few streams.

Foods

Fish, small crayfish, or even snails, but insects, both terrestrial and aquatic, generally make up the bulk of their diet. In streams with watercress, brookies feed heavily on scuds, which are small amphipods often found in abundance near springs.

State Record

7 lbs; 19.75 in - Fountain Springs, Delaware County, July 1996 - Doug Kovarik, Marion, Iowa

Expert Tip

Use fine line and approach pools quietly to improve your fishing.

Details

Brook Trout live in cool, clear headwater spring ponds, springs, and spring-fed streams with shallow riffles over gravel and rubble bottoms. Synonymous with the cold waters, Brook Trout are seldom found in water with temperatures higher than 50-60 degrees. Needing the coldest and cleanest of stream conditions, Brook Trout are highly sensitive to pollution, siltation and poor water quality.

Wild Brook Trout are among the most beautiful of all fish at spawning time. Male trout, during this late fall period, develop a deep red-yellow-crimson coloration along the belly. The sides of the fish often have many red and pale yellow spots, with each spot sometimes surrounded by a blue-colored circle.

Brook Trout spawn from late October to November. Females build redds or nests in clean gravel areas, often near the headwaters of spring-fed streams. Females can sense upwelling springs or other gravel areas with groundwater flow and often deposit their eggs in these habitats. At a constant water temperature of 50 degrees, the eggs will hatch in about 45 days. In colder water, the eggs might not hatch until January or February. The tiny fry stay buried in the stream gravel and survive on natural nutrients stored in the yolk sac until the water temperature starts to rise in early spring. At this time, the fry swim up through the open crevices of the gravel bottom and start looking for tiny insect life to eat.

Females mature at about two years of age, with most males becoming mature during the first year of life. Young females spawn between 200 to 500 eggs, but a larger fish may produce 2,500 or more. Brook Trout reach 3- to 6-inches long the first year, 7- to 9-inches the second, and 10- to 13-inches in the third year of life. Brook Trout weighing over one pound are considered a trophy, since life expectancy is seldom more than three years.

Brook Trout live in the confined areas of our small streams, often spending most of its life in a single pool-riffle. Three habitat components are needed for Brook Trout to survive: resting areas in pools, feeding sites near riffles or swiftly flowing water, and escape cover which is normally found along undercut banks, beneath tree limbs or under large rock ledges.

Recent stream sampling information is available from Iowa DNR's biological monitoring and assessment program.

Sources:

Harlan, J.R., E.B. Speaker, and J. Mayhew. 1987. Iowa fish and fishing. Iowa Conservation Commission, Des Moines, Iowa. 323pp.

Loan-Wilsey, A. K., C. L. Pierce, K. L. Kane, P. D. Brown and R. L. McNeely. 2005. The Iowa Aquatic Gap Analysis Project Final Report. Iowa Cooperative Fish and Wildlife Research Unit, Iowa State University, Ames.

Illustration by Maynard Reece, from Iowa Fish and Fishing.