Brook Trout

The Brook Trout (Salvelinus fontinalis) is the smallest of the native salmonids of Vermont, and is also called the "squaretail." The most distinguishing feature of the brook trout (or wild "brookie") is its adipose fin, or small fin on the back located directly in front of the tail. This characteristic is shared only by other salmonids and no other fish species.

Brook trout have a brilliant orange belly which is particularly apparent in spawning males, and is thought by many to be our most beautiful fish. Its dark olive-green back is laced with darker worm-like markings. Red spots with bluish halos highlight the body. The lower fins are pink or reddish with their leading edges margined in white.

Habitat

Water temperatures are the most important factor in Brook Trout habitat. It thrives in water temperatures of near freezing (32°Fahrenheit) to about 65°F. Temperatures between 55°F and 60°F are most ideal. Although the Brook Trout will tolerate brief periods of temperatures up to 72°F, they will die if exposed to temperatures of 75°F for only a few hours.

Brook Trout also tolerate a wider range of pH levels than Brown Trout or Rainbow Trout, from the extremely low level of 3.5 to a high of 9.8 in laboratory studies. In natural conditions, a more realistic range is between 6.5 and 8.0.

Optimal Brook Trout habitat in streams is characterized by:

  • Having as many pools as there are riffles, or shallow parts of the stream that have choppy water;
  • A rocky bottom with no silt;
  • Clear, cold spring-fed water with stable flow and temperature;
  • Stable banks with a lot of plant growth, and abundant in-stream cover.

Brook Trout also tend to prefer areas out of the main flow with relatively low water speeds (about 0.5 feet per second) and overhead cover such as boulders, vegetation, fallen trees or large woody debris, and undercut banks.

In lakes and ponds, Brook Trout tend to inhabit shallow, spring-fed areas less than 15 to 20 feet in depth. During periods of hot weather, they will seek shallow, cold-water pools of water that well up from the ground rather than retreat to colder depths.

Reproduction

In Vermont, Brook Trout are of the slow growing and short lived, rarely exceeding 3-4 years of age. Many headwater mountain streams rarely produce Brook Trout larger than 6-7 inches. In more productive waters, especially lakes and ponds, they can live longer and achieve maximum lengths of over 20 inches and weigh more than five pounds.

The age at which Brook Trout are able to reproduce varies among populations. Males may mature as early as their first year of life, but usually mature in their second year. Females mature in their second or third year.

Brook Trout generally migrate to spring-fed areas of headwater streams to spawn when water temperatures decline to 40°F to 50°F, usually in late-September through November, although the migrations are not as obvious as with other trout species.

Some individuals may spend their entire lives in a small area of a stream if suitable habitat exists. Lake- and pond-dwelling populations migrate into tributaries or can also successfully spawn on lake-bottom areas of spring-fed pools.

Spawning occurs at water temperatures of between 40°F and 50°F. The female excavates a shallow hole, also called a redd, over a groundwater upwelling or the tail of a pool, in gravel. The male fertilizes the eggs as they are deposited, and the female follows and covers the eggs with gravel. Eggs may be deposited by one pair of trout over a series of small redds.

In Vermont, eggs spend the winter in the gravel. Incubation takes from about 45 days at 50°F to 165 days at 37°F. Newly hatched fry remain in the gravel until their yolk sac is absorbed. Then they come out of the gravel and live in a shallow area of the stream, with low water speeds and with rocks big enough to resist shifting. When they grow into the juvenile stage, they will move into swifter riffle areas.

Diet

Brook trout eat whatever they happen to see, although they prefer drifting bugs, or aquatic macroinvertebrates (e.g., stoneflies, mayflies, caddisflies), to bottom-dwelling bugs when available. Larger individuals may feed on smaller fish, especially in lakes. The brook trout is more of a daytime feeder than either the brown or rainbow trout.

Management

In Vermont, over 180 lakes and ponds and 3,800 miles of streams and rivers are managed by the Vermont Department of Fish & Wildlife for one or more trout species. The department must decide whether or not to stock an area, where to set length and creel limits and gear restrictions, and when and where to allow or not allow fishing by anglers.

The general areas the state considers in management are:

  • Habitat capacity, or quality and quantity of existing fish habitat in the water;
  • Fishing pressure, or how heavily people fish the area;
  • The productivity or food base of the stream, river or lake;
  • The present species of fish that are managed in the body of water;
  • Whether natural reproduction of the trout species would be supported;
  • Timing and duration of spawning runs;
  • Public input.

Steps the Vermont Fish & Wildlife Department make in managing trout in Vermont start with monitoring and evaluating the existing trout population. Biologists take care to protect the selected habitat of the trout and partner with others to implement restoration efforts according to their evaluations. After evaluating the stream, river or lake, they stock trout if needed.

Stocking is determined with one of their three techniques: "put-grow-take," "put-take," or "species recovery" (specific for Atlantic Salmon).

  • Put-take: Catchable-size trout (greater than 6" and often 8-10" long) are stocked in areas where fishing pressure is high, but habitat does not support sufficient natural reproduction or growth of young fish to meet fishing demands. Put-take stocks are removed by fishing usually within one season. The fish that are not caught, rarely survive to the following season. This method of stocking is used primarily in rivers and streams.
  • Put-grow-take: Smaller-sized fish stocked in spring to "grow" to catchable size before being caught. Often used in ponds and lakes where fish can survive the winter and where adequate food is available for fish survival. This technique is usually used to maintain populations where spawning habitat is lacking.
  • Species Recovery: Stocking of fingerlings with the goal of reestablishing the trout species in a particular body of water.

Status

Providing habitat conditions are suitable and competition with other species is minimal, wild Brook Trout populations are found in most streams and in many ponds throughout Vermont. It is the one trout species most likely to be encountered in small headwater streams and beaver ponds. In larger waters, Brook Trout often coexist with Brown and/or Rainbow Trout, or in some instances have been replaced by these non-native trout species.

Even though the Brook Trout is typically identified with streams, wild populations do exist in some cold-water lakes and ponds. Optimal lake and pond habitat has clear, cold, deep water. In addition to spawning in feeder streams, spawning may occur in the lakes where gravel deposits associated with spring-water upwellings occur.

There are not many lakes and ponds with wild Brook Trout populations in the state, and the few that exist are in remote places in the Green Mountains and the Northeast Kingdom. There are, however, small beaver ponds throughout the state with wild Brook Trout populations.

Stocking allows fishing in lakes and ponds that are otherwise not capable of supporting wild trout populations. Many of Vermont's lakes and ponds are almost ideal habitats for Brook Trout, except that they are unable to support natural reproduction due to inadequate spawning areas and are also are inhabited by other competitive fish, which eat smaller Brook Trout.

If the Brook Trout cannot reproduce and survive on its own, it will have to be raised elsewhere and brought to the lake or pond when it is big enough. The public lakes and ponds of Vermont are stocked with fish raised in state hatcheries. More Brook Trout are reared in the state hatchery system to stock public waters than either Brown Trout or Rainbow Trout. Waters that have nearly ideal habitat conditions are sometimes managed for put-grow-and-take fisheries; others with less suitable habitat are stocked with catchable-size trout on a put-and-take basis.

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Vermont Department of Fish & Wildlife
Commissioner Louis Porter

1 National Life Drive
Fish & Wildlife LogoDavis 2
Montpelier, VT 05620-3702
802-828-1000
fwinformation@vermont.gov

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