In my weekly fishing reports, I often encourage anglers to keep stocked trout and release wild ones. Hatchery fish are supplied by Idaho Fish and Game for fishermen to catch, so there’s little reason not to take some home for the frying pan. Wild fish, on the other hand, are bigger, rarer and more colorful — not to mention responsible for repopulating our rivers.
Many anglers I talk to are enthusiastic about maintaining wild fish populations. But how, some ask, do you tell the difference?
For the sake of simplicity, we will stick to rainbow trout. The majority of Idaho hatchery fish are rainbow trout, especially in the Southwest Region, which includes Boise.
So there you are at your favorite Boise River fishing hole. You cast into the depths of a blue-green pool and boom! Fish on. You land the fish and sure enough, it’s a rainbow.
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Now, it’s time to do some investigation.
I usually start with the fins. Wild rainbows have really large fins that are pinkish or greenish in color with beautiful white tips. A hatchery trout’s fins aren’t as vibrant in color, and many have appendages that are partially missing or worn down to a nub — evidence that the fish spent time in a concrete holding tank. A rounded or worn-down nose is another telltale sign.
Some folks think to look for the small, fleshy adipose fin near the tail. In anadromous species like steelhead and chinook salmon, Idaho Fish and Game clips off the adipose fin of hatchery fish. But hatchery trout’s adipose fins typically aren’t removed.
The fins, to me, are the easiest way to identify a wild fish, but the trained eye can pick up a few others. Color is one. Wild fish tend to have more dramatic coloration and spotting patterns. In particular, the red band along the side is usually darker and more pronounced in wild rainbows.
Size also is a good indicator. Most hatchery fish go into the river in the 10- to 12-inch range. Some survive for several years and grow larger, but in my experience, almost all truly big river rainbows — beautiful fish in the 18- to 20-inch range — are of the wild variety. I prefer to keep those in the gene pool.
Almost all of the trout you’ll catch in local ponds and popular lakes and reservoirs such as C.J. Strike, Lucky Peak and Cascade came from the hatchery. But learning to identify a wild river rainbow so you can watch it swim off to fight another day is a one-of-a-kind feeling. Give it a try this fall and you just might be hooked.
Jordan Rodriguez has been fishing Idaho waters since he was a teen. Share your fish stories, adventures, tips and tricks with him at firstname.lastname@example.org.