Fish

Suggested Citation: Kerr, Andy. 2000. Oregon Desert Guide: 70 Hikes. Seattle: The Mountaineers Books. pp. 60-61.

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Fish in a desert!? Certainly. It is difficult to estimate the number of fish species in the Oregon Desert, primarily because scientists are still naming and renaming them. Fish populations once thought to be the same species are turning out to be different subspecies, having evolved in isolation from each other. Suffice it to say that numerous species, subspecies, and varieties of trout, minnow, suckers, and other kinds of fish, both native and exotic, can be found in the desert.

During the Pleistocene epoch (2 million to 10,000 years ago), the basins between the mountain ranges were often huge lakes. As the climate changed, the big lakes dried into smaller ones. Lake Warner, for example, lowered to become the Warner Lakes. Lake Abert and Summer Lake were once one lake. Malheur Lake was much bigger than today. The Fort Rock–Christmas Valley area today has no large lake save the mostly dry Silver Lake, but one can still see the shore-

line etched on Fort Rock, just as can one see on Catlow Rim the shoreline of the lake that once filled the Catlow Valley.

As the lakes lowered, fish populations became isolated and eventually speciated. Scientists can distinguish a dace that lives only in a single water body. The only home to the Fosket speckled dace (Rhinichthys osculus ssp.) is Fosket Spring.

Irrigation withdrawals and/or the cow bombing of streams has diminished the habitat of numerous fish species native to the Oregon Desert. Some are on the federal endangered species list, and others should be.

The 4-inch-long Borax Lake chub (Gila boraxobius) is found only in Borax Lake in the Alvord Basin. It has evolved to live in 97-degree Fahrenheit water.

The Warner sucker (Castostomus warnerensis)—lordy, do we need more charismatic names for these fish species—is found only in the Warner Basin. Fish hang out not only in lakes, but also in the streams of the desert.

Trout, especially the Great Basin redband (Oncorhynchus mykiss ssp.), are also in trouble. The Great Basin redband is known to have six populations, which may actually be six distinct subspecies: Fort Rock Basin, Chewaucan Basin, Warner Basin, Catlow Basin, Goose Lake Basin, and the Harney Basin. The populations have been isolated for at least ten thousand years.

The Great Basin redband is a subset of a large inland redband group, which are cousins to steelhead and rainbow trout. The inland redband trout occur in arid areas between the Rocky Mountains and the Cascade and Sierra mountain ranges from British Columbia to Mexico. It is extinct in three-quarters of its original range. Over the millennia, the species has adapted to severe climate changes and water fluctuations by retreating to refugia when conditions are challenging and expanding when conditions are accommodating.

With a distinctive red stripe, redbands occur in semipermanent lakes, streams, and marshes. They have been found in streams with 75 to 80-degree Fahrenheit temperatures in summer, clearly lethal for their cooler kin. However, degraded desert streams often have temperatures in excess of 80 degrees—deadly even for the redband.

Redband trout are an excellent indicator of stream health, and few streams are healthy in the Oregon Desert. Grazing, logging, roading, mining, and irrigation withdrawal have degraded streams and therefore the redband populations. The introduction of exotic fish species and hatchery rainbow trout has exacerbated an already horrible situation.

Several other fish species of local note are described in various wilderness sections.