Saving Bull Trout in Sun Creek

Bull trout (Salvelinus confluentus) and dolly varden (Salvelinus malma) were once considered to be the same species. They have been separated because of genetic, morphological, and behavioral differences. In general, bull trout are the “inland” form, while dolly varden migrate to the ocean (where they spend much of their adult life) and return to reproduce in freshwater. This makes the dolly varden an anadromous fish, similar in behavior to salmon.

Once found in most major river systems in the Pacific Northwest, bull trout distribution has been significantly reduced over the past 30 years and many local extinctions have occurred. Oregon’s Klamath River Basin represents the southern Limit of present day bull trout distribution. The Klamath populations are genetically distinct from other populations in the region and are now restricted to cold headwater streams. Habitat degradation and introduction of non-native fish species are believed to be the primary causes for the decline. Bull trout have been Listed as a Category 2 Species (candidate species under the Endangered Species Act of 1973) by the U.S. Fish and Wildlife Service (USFWS) and is listed as a sensitive species by the State of Oregon.

Bull trout were probably the only fish species present in Sun Creek, a high elevation, second order stream, prior to early introductions of non-native salmonids. National Park Service (NPS) and Oregon Department of Fish and Wildlife (ODFW) records indicate repeated stocking of rainbow trout (Oncorhynchus mykiss) and brook trout (Salvelinus fontinalis) in Sun Creek between 1928 and 1971. The only park-wide stream survey conducted during this period took place in 1947. A seasonal naturalist named Orthello Wallis (who later became the first aquatic biologist ever employed by the NPS) found bull trout, rainbow trout, and brook trout in Sun Creek.

A resurvey of Sun Creek was made in the summer of 1989 to investigate the distribution and abundance of fish relative to habitat characteristics. The survey was funded as part of Klamath River Basin water rights adjudication. Sun Creek was surveyed from its headwaters to the park boundary. Bull trout, brook trout, and hybrids from the two species were collected. No rainbow trout were collected in the portion of Sun Creek within the park and may no longer exist in the stream.

Investigators observed that habitat utilization by bull trout and brook trout was very similar. Competition and hybridization with brook trout have probably reduced the distribution of bull trout in Sun Creek. Bull trout were restricted to a 1.9 km reach of the stream and the total number of adult bull trout was estimated at 130 fish. Such a low population density is alarming, since it suggests that local extinction could occur within the next few years.

The NPS is developing a bull trout management program whose goals are to remove brook trout from Sun Creek, build a barrier to prevent re-invasion, and to re-establish a self-sustaining population of bull trout in Sun Creek within Crater Lake National Park. During 1991, park staff convened a “Bull Trout Recovery Team” to develop recommendations on how to best achieve these goals. It consisted of representatives from the NPS, USFWS, ODFW, U.S. Forest Service, California Department of Fish and Game, and Oregon State University. A final report from the group is expected in early 1992 and will form the basis for the first active fish management project ever undertaken in the park. An environmental assessment will be available for public comment before any management action is taken.

Visitors should note that fishing for bull trout in Crater Lake National Park and throughout south central Oregon is prohibited by state law. Bull trout within the park are also protected by federal regulations. Fishing for other species in most park streams is permitted. Copies of fishing regulations are available at the park’s visitor centers. Fishing in Crater Lake for kokanee salmon (Oncorhynchus nerka) and rainbow trout (Oncorhynchus mykiss) is allowed. No state license is required and fishing on the lake has been good in recent years.

Mammals of the Pumice Desert

Much of the Crater Lake National Park is covered in forest. One visible exception is the Pumice Desert on the road to the park’s north entrance. At first glance this 5 1/2 mile square, nearly flat opening appears to be quite barren except for a few scattered lodgepole pine (Pinus contorta). A closer look reveals that many forms of life, including several mammals, use this landscape as a habitat.

At a mean elevation of 5,960 feet, the Pumice Desert is in the Klamath River drainage basin. Yet it is but two miles from the Umpqua River and Rogue River tributaries. Elizabeth Mueller Horn studied the ecology of the Pumice Desert and described the vegetation, which largely consists of herbaceous plants with very sparsely scattered lodgepole pine. She found only 14 plant species with total cover of 4.6 percent. All plants except the lodgepole pine are small herbaceous or woody stemmed forms with various adaptations for surviving in the absence of summer surface moisture and relatively high temperature. The poorly developed soil is relatively porous and deficient in several minerals, a further cause of the depauperate flora. The resulting lack of cover increases daytime summer temperatures, creating a relatively unique park habitat resembling parts of the Great Basin Desert to the east.

Interestingly enough, several animals are adapted for living in the Pumice Desert’s rather harsh micro-habitat. Mammals are an excellent example of the way in which some animals cope with the conditions of extreme temperatures and seasonally restricted food and water. The mammals that occupy the Pumice Desert are either well adapted for living in these restrictive conditions, or are highly mobile, and use the area on a temporary basis, or are simply passing through during movement to more preferred habitat. Field studies by one of us (Monical) indicate that only three mammal species appear to be permanent residents, far fewer than in other park habitats. The Great Basin pocket mouse (Perognathus parvus) and the deer mouse (Peromyscus maniculatus) occur in significant numbers. One summer’s live trapping (168 traps set for ten nights) resulted in the capture of 54 individual pocket mice and 46 deer mice.

The Great Basin pocket mouse, a seed-eating specialist, is common in the high desert habitat of western North America. It carries food in its fur lined cheek pouches for storage in a burrow. The ability to metabolize moisture from its food allows the pocket mouse to survive with no free water This nocturnal species also closes its burrow during the day to help maintain a moist environment. When conditions become too severe, it will estivate in the summer or become inactive during the winter.

The deer mouse is the park’s most ubiquitous species, utilizing many different habitats. A highly omnivorous animal, it is able to survive on a variety of vegetative parts, insects, and has even been known to eat other small mammals. Though mostly nocturnal, the deer mouse at times can be seen just before dark when it begins its search for food. An additional adaptation leading to its continuing survival in harsh conditions is its high reproductive rate.

A third, less abundant, resident is the western pocket gopher (Thomomys mazama). Its mounds are seen on the periphery of the desert near the forest edge, where the texture of the pumice soil is more conducive to its underground habits. Gophers are active in the winter and sometimes fill their above-ground burrows under the snow with soil. After melt, these serpent-shaped ridges are evidence of the previous winter’s activity.

Other captured or observed rodents, considered transients, are the yellowpine chipmunk(Tamias amoenus), golden mantled ground squirrel (Spermophilus lateralis), bushy tailed woodrat (Neotoma cinerea), and porcupine (Erethizon dorsatum). It is also likely that snowshoe hares (Lepus americanus), mule deer (Odocoileus hemionus), and perhaps elk (Cervus elaphus), occasionally venture into this area of marginal habitat. Some species of bats that roost in the nearby forest use the open areas for foraging. Predators are rare but could include the red fox (Vulpes vulpes), coyote (Cants latrans),ermine (Mustela erminea), and long- tailed weasel (Mustela frenata). The pronghorn antelope (Antilocapra americana), sometimes sighted in the park, is known to use open areas such as the Pumice Desert. This location represents one of the westernmost extremes of the current range for this species, usually a Great Basin inhabitant.

Mammals utilize the Pumice Desert for a variety of reasons, even though the harsh environmental conditions preclude most as residents. The presence of the Great Basin pocket mouse as a permanent inhabitant there creates a unique combination of species for Crater Lake National Park.

L. Howard Crawford, Nature Notes, Vol. VIII, No. 3, September 1935.