Saving the Bull Trout

by Craig Knowles and Robert Gumtow

Table of Contents

Bull trout; photo by Forest Service biologist Russell Thurow.


Native to the Pacific Northwest, including Montana,
Idaho, and northern California and Nevada, the bull
trout has some of the most demanding habitat requirements of any native trout species--mainly because it requires water that is especially cold and clean. Abundant a century ago, dams, siltation from logging and farming, and efforts by state game agencies to poison it have greatly reduced its numbers and range.

In 1992, a Montana Department of Fish, Wildlife and Parks review of the status of the trout in Montana found that bull trout occupied less than half of their historic range. The remaining population was fragmented, meaning many isolated communities of bull trout might not have enough numbers to maintain a viable population.

After this report came out, several Montana-based conservation groups petitioned to have the bull trout listed under the Endangered Species Act. After reviewing the fish's status in 1994, the Fish & Wildlife Service decided that listing was "warranted but precluded" because other species that were more in danger needed listing first. While the bull trout is threatened, as defined by law, its numbers and distribution remain sufficient to insure that it is not at immediate risk of extinction. Today, the bull trout remains one of 179 "candidates" for listing.

Life History of the Bull Trout

Bull trout are a member of the North American salmon family, which includes salmon, trout, whitefish, charr, and grayling. Members of this family tend to prefer cold, clear waters, and the bull trout is exceptional for its demand for especially cold--no more than 64deg. F--water.

Salmonids are particularly known for their migratory nature. Anadromous salmon are an extreme case, spending most of their lives in the ocean but returning to headwaters streams to spawn. Resident trout are at the opposite end of the spectrum, spending generation after generation in one stream. Between these extremes are migratory fish that never reach salt water, including adfluvial fish, which spawn in streams but live in lakes; and fluvial fish, which spawn in headwaters streams but live downstream in larger rivers.

Various populations of bull trout fit at all ranges of this spectrum. Many are resident to a single stream; others migrate on a fluvial or adfluvial basis. And one population of bull trout in Washington is known to be anadromous. Presumably, the various types of trout interbred at times, which helped maintain viable populations throughout the fish's range.

The bull trout received its name from its large head and mouth. It is also distinguished by its predatory nature, and its diet as an adult consists largely of other fish. But when given an opportunity it has also been known to eat frogs, snakes, mice, and ducklings.

Until recently, the bull trout was considered an inland form of the Dolly Varden (Salvelinus malmo), an anadromous trout found in coastal streams. In 1978 biologists decided it was a separate species, and named it Salvelinus confluentus.

The bull trout may have been anadromous during the last glacial period, when cold, clear streams were more abundant than today. This would explain its occurrence in isolated drainages throughout the Northwest.

Bull trout can live up to ten years and are sexually mature after four. They spawn every year or every other year and require particularly clean gravel bars for their redds (nests for eggs). If 20 percent of the solids in a gravel bar are fine sediments, spawning success falls by more than 50 percent; 40 percent fine sediments reduce success by 99 percent.

Spawning success is even more sensitive to temperature. Although adults can stand water temperatures up to 64deg. F, eggs do best with temperatures of no more than 36deg. F. Temperatures above 46deg. F can reduce survival by at least 75 percent.

Causes of Bull Trout Decline

Scattered distribution and demands for cold, clear waters make bull trout especially susceptible to the standard formula for extinction: Although biologists have been aware of declining bull trout populations for at least two decades, little has been done to reverse the decline until the past three or four years.

No one did a bull trout census in 1896, but what records are available indicate that bull trout populations were healthy at that time. The trout's problems almost certainly began with impoundments for irrigation. Irrigation creates at least four major problems for bull trout:

Life for the bull trout was complicated further by the construction of major dams throughout the Columbia River drainage system. Between them, the dams and irrigation wiped out many, if not most, of the migratory varieties of bull trout.

The bull trout that are left are mainly resident trout located in headwaters streams. This means that populations are highly fragmented; where once the migratory bull trout linked resident bull trout to much of the species' gene pool, today the residential populations are isolated and vulnerable to habitat degradation.

Forest practices are the most important cause of habitat degradation for these resident trout, followed by agriculture, grazing, and mining. Most of these practices silt up the streams that trout need for survival, and such siltation can be especially damaging to spawning gravels.

More than 80 percent of all bull trout populations are threatened by one of these land management practices. The strongest populations of bull trout tend to be in unmanaged roadless areas that have near-pristine streams. Recent salvage sale legislation has put many of these roadless areas in danger of being logged.

Tinkering with various forms of habitat degradation works synergistically to affect overall change. For example, logging or overgrazing often removes riparian vegetation. This reduces the amount of instream woody debris--a critical component of bull trout habitat. The reduced stream cover also increases stream temperatures, often exceeding the 64deg. F limit to which bull trout are so sensitive. These activities also tend to increase overland runoff to streams, adding to sediment loads and spawning area degradation.

As if these problems weren't enough, state game management programs have seriously harmed the bull trout. In a remarkable parallel to the story of the wolf, fish managers deliberately tried to exterminate bull trout as early as 1913 and as late as 1990.

Around the turn of the century, game managers began introducing brook trout and other popular, but non-native, fish to Northwest streams. Due to its predatory nature, the bull trout was not considered a desirable part of stream ecosystems; why make the effort to plant game fish if a native fish is going to eat them all?

As a result, in 1913 and 1914, Montana attempted to eradicate the species through commercial net fishing. Bounties for bull trout and poisoning campaigns continued as late as 1990. Some of the later poisoning programs were not directed solely at bull trout, but fish managers knew that bull trout were there. Many of the poison efforts were paid for with federal funds under the Dingell-Johnson program.

The brook trout posed another problem for bull trout: It is genetically close enough to bull trout to permit hybridization, though the offspring are infertile. Brook trout reproduce faster and can stand slightly warmer, slightly dirtier water than the bull trout, so when the two are in competition the brook trout inevitably wins.

State agencies have halted their anti-bull trout programs, but individual populations of bull trout remain vulnerable to catastrophes. Natural catastrophes might include introduced disease or drought, while human-caused catastrophes would include road construction and landslides induced by timber cutting.

Chances of Survival

In terms of absolute numbers, plenty of bull trout are left. State fish biologists have identified a total of 438 different populations. The total Northwest-wide bull trout population may be between 0.5 and 1 million individuals.

The problem is that dams and other activities have wiped out most of the migratory bull trout populations, leaving mainly resident fish. This means that the 438 remaining populations are often isolated from one another. Many of these scattered groups have just 200 to 1,000 individuals each. Genetically, these numbers are too small to assure survival; conservation biologists estimate that at least 2,000 individuals are needed to maintain genetic health and diversity.

Protection of these 438 groups should be sufficient to assure bull trout survival in the short run. But long-run recovery will require changes in downstream conditions to restore all the migratory populations.

One thing is certain: While the remaining populations are vulnerable to natural catastrophe, the actual causes of bull trout decline have almost entirely been government-subsidized programs. Federal hydroelectric dams and subsidies to irrigators did most of the damage to migratory bull trout. State introductions of exotic trout and poisonings of resident fish--often with federal funds--may have finished the job. Now, federal subsidies to national forest timber cutting and livestock grazing represent the greatest threat to the bull trout populations that are left.

Recovery Efforts to Date


Montana has more than half of all surviving bull trout populations, yet it was the first to recognize--or at least do something about--the bull trout's deteriorating condition. In late 1993, Montana's governor set up a Bull Trout Roundtable that will develop and implement a recovery plan in that state.

The roundtable includes a restoration team comprised of agency administrators and interested public; a scientific group comprised of biologists with extensive fisheries experience; and watershed groups comprised of residents living within one of twelve watersheds used by bull trout. The restoration team will, with guidance from the scientific group, write separate restoration plans for each of the twelve watersheds. The watershed groups will then be asked for input and advice on how to implement the recovery effort.

The 1995 Montana state legislature appropriated $1.6 million for stream restoration work focused primarily on bull trout. The majority of this work is being concentrated on the Blackfoot River, which is being used as a model for the other eleven watersheds. Stream restoration has consisted of screening irrigation water intakes, and fencing key riparian areas from cattle grazing.

The Department of State Lands has voluntarily discontinued timber harvest in management zones along streams inhabited by bull trout. Montana Department of Fish Wildlife and Parks has also closed nearly all legal harvest of bull trout in the state. In addition, the confluences of important bull trout tributaries are seasonally closed to fishing for the protection of bull trout during spawning. Montana is also working on public education concerning bull trout conservation and plans to increase law enforcement efforts to prevent poaching.

Although there are many factors still working against bull trout restoration in Montana, state agencies and politicians have each made a commitment to recover the species. Many factors, such as downstream impediments to migratory varieties of bull trout, are beyond the state's control. However, Montana Department of Fish, Wildlife and Parks personnel are dedicated to restoring bull trout and express confidence in their program.


Following the Fish & Wildlife Service's warranted-but-precluded ruling, Idaho Game and Fish made an early effort to develop a bull trout restoration plan, but this effort did not include public or political input. Momentum for this restoration plan was lost with a change of administration, but just recently the Governor of Idaho has committed the state to work on bull trout conservation in a manner similar to Montana.

The governor appointed a ten-member steering committee to make recommendations for bull trout restoration. The steering committee is largely made up of agency personnel and industry representatives, and contains few biologists with bull trout experience. A scientific subcommittee advising the steering committee also lacks practical field experience with the bull trout.

The steering committee made recommendations to the governor's office, which in turn has drafted a bull trout restoration plan that is now out for public comment. In contrast to Montana, however, this plan was prepared without a comprehensive statewide review of the status of the bull trout in Idaho.

Idaho restricted the harvest of bull trout in 1994 and will close all waters to bull trout harvest on 1 January 1996. Idaho is also screening irrigation water intakes. This program has been in place for about thirty years, and more than half of the Snake River's water diversions have been screened. This screening was originally required to protect salmon fisheries, and the Idaho Game and Fish Department is required to inspect the screens.

Oregon and Washington

Oregon and Washington are working on bull trout conservation too, but their efforts are less than those of Montana and Idaho. Although these states have concentrated their resources and management effort on salmon they have restricted the legal harvest of bull trout.

The Washington Department of Fish and Wildlife prepared a status report on bull trout in 1992 and subsequently substantially reduced the legal harvest of bull trout statewide. The state considers the bull trout a "declining species."

Oregon also prepared a bull trout status report in 1992 and has either closed waters to bull trout fishing or limited the daily catch to a single fish. A cooperative effort by state, federal, and private agencies has been remarkably successful at restoring the bull trout in the Metolius River and Lake Billy Chinook. In 1986, biologists were able to find only 27 redds (spawning nests) in this aquatic system. After surveys of habitat conditions and efforts to protect habitat and regulate fishing, the number of redds increased to more than 300 in 1994.

California and Nevada

The bull trout has been extirpated in California and the state lists it as endangered. California has made one attempt to reintroduce the bull trout to the McCloud River but an initial evaluation suggests that the reintroduction has been unsuccessful.

Nevada's single bull trout population is isolated in the Jarbridge River. Some fifty adults are restricted almost entirely to the Jarbridge Wilderness Area. This population faces a high risk of extinction due to its isolation and small size.

State and Federal Cooperation

One of the most important things driving state recovery efforts is a desire to keep the bull trout off of the endangered species list. This isn't entirely altruistic on the part of the states: The listing of the species would give a powerful federal bureaucracy one more excuse to interfere in a business--game fish management--that has traditionally been handled by the states.

Indeed, feuds between state and federal agencies over bull trout recover may be hampering habitat protection efforts. Attempting to maintain their jurisdiction over the species, the states blame the federal land management agencies for destroying habitat. Meanwhile, the federal agencies blame the states for mismanaging or neglecting the fish populations themselves.

Unfortunately, both are right--but that still leaves open the main question: Who should try to rescue the bull trout? State agencies that are closer to the problem and that have better relationships with local residents may be better equipped to recover the species. At the same time, states have little control over the many federal programs that are harming the fish, including dams, irrigation, and timber sales.

Perhaps the most worrisome problem at the moment is the federal salvage sale program. The Payette National Forest, for example, is likely to offer 27 salvage sales that will require about 100 miles of new roads in watersheds inhabited by the bull trout. Sales and road construction are planned on several other forests where bull trout are known to occur, including the Boise (10 miles of new road) and Clearwater (16 miles of new road).

Salvage logging is entirely under the control and jurisdiction of national forest managers. If any isolated bull trout population is lost as a result of salvage timber sales, it will be with the blessings of the Forest Service and Congress.

Experiences with past logging make it seem inevitable that salvage sales and associated road construction in formerly unroaded areas will reduce bull trout populations. Forest Service inventories of landslides resulting from this past winter's flooding, for example, indicate that most were associated with logging roads, many were associated with clearcuts, and few took place in pristine forests.

Karen Pratt has studied bull trout in Lighting Creek, a tributary to the Pend Oreille River in northern Idaho, for more than a decade and has documented periodic landslides resulting from logging and roads. Pratt found that excessive sediment loads during this period turned Lighting Creek into a braided stream and bull trout numbers have substantially declined.

To minimize these types of problems, the Forest Service developed a document titled Inland Native Fish Strategies for the Columbia River basin in 1995. Among other things, the document places a moratorium on logging in buffer strips along riparian zones until a fisheries evaluation of the stream is completed or a Forest Service biologist says no evaluation is needed. The Forest Service has promised its salvage sales will abide by this.

Since the bull trout remains only a candidate species, the Fish & Wildlife Service is not directly involved with bull trout restoration. While it has provided technical assistance to the states, it has not provided any significant financial aide.

Listing of the trout, however, could place an additional check on salvage sales and other harmful activities by federal agencies. At the least, the agencies would have to consult with the Fish & Wildlife Service to insure that such activities would not jeopardize the bull trout. Such consultations, while not perfect, would help relieve worries that salvage sales will destroy some of the remaining bull trout populations.


Once found resident and migrating throughout the Columbia River drainage system, activities that have been largely subsidized by the government have reduced bull trout to a few hundred headwaters streams. While far from extinct, the species is vulnerable to natural and human-caused catastrophes.

State agencies are doing what they can to recover the species, but many of the problems are beyond their control. Yet listing the species seems no more certain, since there is little evidence that the Fish & Wildlife Service has the political backing to oppose the major causes of fish habitat loss. Just as the bull trout waits in line to be listed as a threatened species, its recovery awaits new tools for protecting endangered species.

Craig Knowles is a wildlife biologist in Boulder, Montana and a contributing editor for Different Drummer. Robert Gumtow ( is an environmental consultant specializing in data management in Helena, Montana.

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