The Crescent Lake Trout

Set in the north of Olympic National Park in Washington State, Lake Crescent is a large lake covering more than 5,000 acres and exceeding 600 feet in depth. Two species of wild trout are native to the lake, a variety of rainbow trout which was named Salmo gairdneri beardsleei by D. S. Jordan in 1896 and a lake form of the coastal cutthroat trout Salmo clarki clarki, which has the varietal name crescentis.

Distinguishing between the two was not easy even when they were both abundant, up to the early years of the 20th century. The Crescent Lake rainbow trout, also known as the blueback and Beardslee trout, tended to be much larger, attaining weights in excess of 15lbs, while the speckled trout (as the cutthroat of the lake were known) reached only half that size. But through most of the year their coloration was very similar, a dark steel-grey or blue with different amounts of spotting; the cutthroat had heavier spotting than the rainbow. Only at the onset of the breeding season did the differences between the two really become apparent, when the cutthroat developed its characteristic red flashes on the throat and the rainbow exhibited its iridescent flanks.

Identification today is considerably more difficult. Between 1920 and 1975 stocks of several other varieties of rainbow trout and cutthroat trout were introduced into Lake Crescent. During the 1970s it was possible to catch trout of almost all shapes, sizes and colours without being certain that any individual was either the native rainbow or cutthroat. Doubts were expressed that these native strains could ever have survived in a pure state.

However, research carried out in the early 1980s by Bryan Pierce of the Colorado State University demonstrated that both species of wild trout have survived in the lake, genetically intact. No further stocking of non-native fish is being carried out, and as anglers remove the remaining stock of introduced fish, Crescent Lake might yet revert to the days when it had just it's two forms of wild trout.

These two very close species coexisted without interbreeding. Old reports demonstrate that the two had quite different ecologies in the lake. The cutthroats spawned before the rainbow trout and in a different place: the rainbows spawned in the mouth of the Lyre River, the outflowing stream, while most of the cutthroats bred in the inflowing Barnes Creek or else in the lower reaches of the Lyre River.

Some degree of competition was further avoided by the young cutthroats remaining in their natal streams for the first two years of life, while the rainbow trout fry entered the lake immediately after leaving the redds. However, both the Crescent Lake trout fed on the same food sources: small insects initially, and then on a diet of fish (notably, the kokanee, a form of landlocked sockeye salmon), which resulted in fast growth rates.