The Stream Doctor

February 21st, 2005

Email YOUR Questions directly to the Stream Doctor. This is your opportunity to get an experts professional opinion on anything stream related.

Q. Based on the external features of trout, how can I identify the type of trout that I am catching? When I catch a trout, I don't know what kind of trout it is; could you give me a few tips of how to determine whether the trout is a brown, rainbow, brook, speckled, etc...? Thank you.

A. Their are many, many books, pamphlets, etc. which provide the information you are looking for, and many have pictures of each species of trout which will aid you in their identification. I'm sure your local fishery biologist could help you locate some of these. Below are some general features of each species that should help you in identifying the main trout species:

Rainbow trout (Oncorhynchus mykiss): Generally silvery with dark olive green back and black spots. It gets its name from a red or rosy band along its side extending from the gill covers to just in front of the tail. There is great diversity in this broad group, especially in the distribution of the spots on the body.

Brown trout (Salmo trutta): Again, there is great diversity in the coloration of brown trout. Generally, they are olive green to brown on the back, shading to yellow or white on the lower sides and belly. There are two colors of spots. Black spots, surrounded by a light halo occur on the backs and sides, and red or orange spots, again with a light halo, are found on the lower sides. The dorsal, anal, and pelvic fins have sometimes have leading edges fringed with white and black, although this is not as distinct as for the brook trout (see below). The brown trout is the only trout species that has red on the adipose fin (the small fin on the back just in front of the tail), although this color character is often absent in hatchery-reared fish.

Cutthroat trout (Oncorhynchus clarki): The name comes from the presence of a red or orange slashmark found on each side of the lower jaw; however, you must use this character with caution because other trout - rainbow/cutthroat hybrids, Gila trout, Apache trout, and the redband trout (a subspecies of the rainbow) - often have this mark as well. There are more subspecies of cutthroat trout than any other species of trout, so other than this distinguishing mark, they are difficult to tell apart without experience. Generally, the bodies are yellowish to olive green and are black-spotted. It is the pattern and size of the black spots that are most useful in distinguishing sub-species.

Brook trout, speckled trout (Salvelinus fontinalis): These are two of the many common names for this trout, which, in fact, is not a true trout but a char. It is quite easy to distinguish from the other species. The dark, greenish-black back is patterned with lighter colored, worm-like markings called vermiculations. They have no dark spots, unlike the other three trouts, but have red spots surrounded by a bluish halo. The lower sides and belly shade into orange, which can be truly spectacular, especially during spawning season. Probably the best way to identify brookies is by the fact that the pectoral, pelvic, and anal fins have a white leading edge bordered by black.

If you have a question, please feel free to contact me.
~ C. E. (Bert) Cushing, aka Streamdoctor
105 W. Cherokee Dr.
Estes Park, CO 80517
Phone: 970-577-1584

The 'Stream Doctor' is a retired professional stream ecologist and author, now living in the West and spending way too much time fly-fishing. You are invited to submit questions relating to anything stream related directly to him for use in this Q & A Feature at

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