Markings and Coloration
The brook trout can be recognized by the wavy lines, or vermiculations,
on its dark, olive-green back--the same pattern created when the sun
shines through rippled water to cast shadows on the bottom. The result
is a camouflage enabling the brook trout to avoid predators from above
such as kingfishers and herons.
The brook trout also typically has many pale yellow spots and a few
small red spots surrounded by blue halos on their sides. They've also
been described as the only trout with light spots against a dark background,
as the brown and rainbow trout have the opposite spotting pattern
(dark spots on a paler background).
The brook trout's pectoral, ventral, and anal fins are starkly edged
in white, which again is unique among other common trout. The white
is the main giveaway. Even when the brook is motionless, the white-edged
fins will call your attention to the fish. The highly visible, white-edged
fins are a definite disadvantage when it comes to the brook's predators.
Another characteristic is a relatively large head and mouth, and
the head may amount to one quarter of the body length on adult fish.
During their fall spawning period, the lower flanks of males become
brilliant orange and older males may develop a slightly hooked lower
If you are still in doubt after checking all the previous characteristics,
feel along the center of the mouth's roof with your fingertip. The
vomerine bone has teeth in a small cluster at its forward end. If
you find teeth all along the roof of the mouth, you didn't catch a
Because the brook trout is deep bodied in proportion to it's length,
it can swim efficiently in water as shallow as their body depth. Their
maneuverability is an asset in capturing a wide variety of foods in
waters of all depths. The powerful, long run of a large rainbow or
brown when first hooked is almost always absent with large brook trout,
which tend to a bull-dog tugging and twisting fight near the bottom.
Such a fight is part of their nature, determined in turn largely by
Brook trout prefer cold, clear streams and are the most cold tolerant
of all common trout.
Range and Habitat
As a general case, brooks are native to the northern half of the
eastern United States in addition to eastern Canada. There are some
brook-trout populations as far south as Georgia along the Appalachian
spine, but these have been in decline since at least 1900 and probably
earlier, when both logging and overfishing destroyed trout habitat
at lower elevation and the more accessible areas of highland streams.
In Great Smoky Mountain National Park on the Tennessee-North Carolina
border, where log-ging was essentially eliminated with the park's
establishment in 1936, brook-trout populations have continued to decline.
The apparent cause is competition from rainbow trout that were first
introduced to this area in 1910 and are slowly displacing the remaining
brook trout higher and higher into the region's headwater streams.
These head-water areas could be the brook trout's last refuge here
as the rainbows' upstream movement may be finally limited by physical
barriers such as waterfalls or other obstacles created by Park personnel
on behalf of the brook trout.
Brook trout are inherently cold-water fish, and can perform well
within a temperature range of 40 to 68 degrees Fahrenheit. However,
brook trout have been shown to feed at temperatures as low as 34 degrees,
and the lethal temperature limit of the brook seems to be around 30
The upper limit of a brook trout's tolerance is somewhere between
72 and 77 degrees, which is often reached in the middle and southern
portions of its range in late summer. However, to feed or avoid a
predator the brook might venture briefly into warmer water--but not
Where rainbows are more open-water oriented than brook trout and
depend on insects at or near the lake's surface, brook trout typically
feed more at a stream's bottom.
Few brook trout survive to age four in the wild, so are generally
the shortest lived trout. The growth of the brook trout varies, depending
on such things as habitat, water temperature, and competition from
other fish. Even in productive waters, the brook will rarely weigh
more than 3 pounds by the end of their third year.
Brook trout at spawning time appear to be severely stressed by the
catch-and-release process. The implication is that they should be
left unmolested at this season, even though catch-and-release rules
on some brook-trout waters permit year-round fishing.
The restoration efforts of Park resource managers have led them to
closing some streams and tributaries
to all fishing, and ensuring natural barriers such as waterfalls are
adequate to prevent the brown and rainbow trout from migrating upstream.