With the exception of Dolly Varden trout (Salvelinus malma) in Sun Creek, all of the fish found within Crater Lake National Park are planted exotics. A number of
rainbow trout (Salmo gairdnerii iridus) were introduced into the lake as early as 1888. Other species introduced into the lake are the Coho, or silver salmon (Oncorhynchus kisutch);
the landlocked sockeye salmon (kokanee) (Oncorhynchus nerka); the German brown trout (Salmo trutta); the brook trout (Salvelinus fontinalis); cutthroat trout (Salmo clarkii); and
steelhead trout (Salmo gairdnerii gairdnerii). Only the rainbow and kokanee have been able to adapt and survive in the lake's environment. The kokanee is the best adapted of the two
and the most numerous, with fish averaging 9 to 18 inches in length. While less abundant, the rainbows are the larger, measuring 12 to 24 inches in length. Neither of the fish are
abundant and their numbers seem to be declining.
Freshwater shrimp and crayfish found in the lake are exotic species which have been introduced as a food source for the fish populations.
Four species of trout are found in the park's streams, although only brook trout and rainbow have been planted officially. Large numbers of rainbow have been stocked,
but the survivors are few and scattered. Rainbow have been found in Munson, Annie, Bybee, Sun, and Castle Creeks. Brook trout plantings have been far more successful and this trout is
the most abundant and firmly established fish in the park's streams.
A single specimen of brown trout has been recovered in Sand Creek from above the falls, which appear to form an effective barrier to upstream fish migration. It is
probable that this fish is a survivor of an unrecorded or unauthorized planting in this creek. Dolly Varden are found in Sun Creek, and are considered the only native trout in the
park, having entered Sun Creek from the Wood River and become well distributed in the lower portions of the creek.
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