Copyright 2013 James Marsh
Species of Trout           
There are four (4) basic species of trout that are of interest to the fly angler - the Brown
Trout, Rainbow Trout, Cutthroat Trout and Brook Trout.
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Brown Trout
Rainbow Trout:
The rainbow trout is native to the Western United States. It was at one time stocked
in the park. Rainbows probably average 9 to 12 inches long but anglers occasionally
catch one that is over twenty inches long or better. You will find the rainbow in faster water
out in the open, hiding only under the cover of a broken surface of water. They tend to
feed on the surface more so than the other trout. Of course they will spook very easily if
danger approaches. They prefer temperatures ranging from the mid fifties to the high
sixties. They can survive in water temperatures as low as 32 degrees F and as high as 80
The rainbow is the most sought after of all the species of trout in many rivers. They are
exciting fish to catch. Rainbows tend to jump more than the brown or the brook trout.  
They spawn in the spring. Rainbow trout have a pink or red line that runs from their gill
cover to their caudal fin. They get their name from this rainbow line. Rainbow trout are
native to streams in the Western United States and Canada that flow into the Pacific
Brook Trout:
Brook trout were stocked in Yellowstone at one time. They are now all wild fish. Brook trout
spawn in the fall. The juveniles stay hidden in the gravel until Spring. They average 4 to 8
inches in length and rarely exceed 12 inches. A brook trout found in a stream that is over 10
inches long should be considered a trophy.  

The brook trout has a brown to a dark green basic color with a distinctive marbled pattern  of
lighter shades across the sides and back and extending to the dorsal fin, and often to the
tail. There is a very distinctive scattering of red dots, enclosed by blue colors along the flank.
The belly and lower fins are reddish in color and the fins have white leading edges. Often the
belly, particularly the males, becomes very red or orange when the fish are spawning. They
prefer water temperatures of less than 68 degrees F. They rarely live longer than five years
and usually only three years.
Cutthroat Trout:
The cutthroat trout is the only true native trout that is of prime interest to the fly angler. Brook
trout are technically Char and not trout. Cutthroat trout are native to the Western United
States. Because they have lived and survived in isolated areas in most parts of the West,
they have developed into several distinct sub-species and strains.

Many of the streams in the West include hybrid cutthroat trout called “Cutbows”. Cutthroat
and rainbow trout will interbreed because they are closely related. They produce fertile
hybrids. In waters where both parent species exist there is no way of positively separating the
cutbow from the rainbow and cutthroat where they have interbred. DNA analysis is just not a
practical procedure for anglers.

Native cutthroats are usually a brownish gold color and have relatively large spots. The name
“cutthroat” came from the obvious red mark at the lower part of their gills. Most of the time the
hybrid cutthroat, or cutbows as they are called, have smaller spots than the pure cutthroats.
They usually show a rainbow line but much less noticeable than the rainbow trout. The colors
of the cutbows are more subdued. Normally the stomach is not as yellow as the cutthroat.
Neither is the cut mark or red throat slash as noticeable on the cutbow as it is the cutthroat.
Photo Courtesy of David Knapp Photography
Photo Courtesy of David Knapp Photography
Brown Trout:
The brown trout is originally from Europe. It was at one time stocked in the park's streams.
Of the four trout species, It is the largest to be found in the park. Brown trout are very
difficult to spot in a stream. They can actually change their color to blend in with their
surroundings. They are also capable of resting on the bottom of the stream and when they
do, they look much like the bottom.  

Browns are found mostly in streams in the lower elevations. They prefer water temperatures
ranging from the mid 50's up to the high 60's F. They are capable of surviving in water
temperatures as high as eighty degrees F. Most smaller brown trout, those less than 12
inches long, feed on insects as well as a large variety of other foods. Once they reach a
larger size they tend to change their feeding habitats and prey on bait fish, crustaceans and
even other small trout. This allows a few of them to grow to a very large size. It has always
been assumed that the brown trout hides under rocks and crevices in the banks most of the
day and that they prefer to feed only under low light conditions. This is not nearly as true as
once thought. They will generally feed most of the time they are undisturbed for long periods
of time. It is certainly true that they are very difficult to approach without spooking them and
during the time anglers are attempting to do so, they definitely hide under rocks.

Brown trout spawn in the fall. During this time the trout (especially the males) can be very
aggressive. Both the males and the females tend to lose their normal caution and
completely expose themselves at times. Although anglers find it very difficult to pass up a
large brown trout involved in the spawning process, they should. Catching a big brown trout
while it is spawning and/or protecting its redd is certainly nothing to take pride in even
though it may be legal to do so. In our opinion it is unsportmanlike
Photo Courtesy Steven Lamb