The rapid decline in global biodiversity threatens the natural resources, food security, health, and livelihoods of current and future generations. Anthropogenic activities, including the introduction of non-native species, habitat fragmentation and alteration, and resource extraction, have exacerbated this decline. One such imperiled species are Bull Trout (Salvelinus confluentus), which have exhibited significant declines throughout their range and are expected to decline by >30% over the next 21 years in Alberta. While their decline is attributed to a myriad of threats, the degree to which non-native fishes contribute to their decline is uncertain. The objective of my thesis was to investigate the effects of Brook Trout (Salvelinus fontinalis) and Brown Trout (Salmo trutta), two non-native salmonids, on the habitat use and dietary niche of Bull Trout. To address the habitat component, I developed a multi-species N-mixture model using in-stream and land use derived characteristics to assess how Brook Trout and Brown Trout affect Bull Trout abundance in relation to habitat factors. I determined that Brook Trout negatively affect Bull Trout abundance when streams are less than 11°C and lack habitat complexity. Interactions between Brown Trout and Bull Trout are less certain, but larger, lower elevation streams are likely to see reductions in Bull Trout abundance where Brown Trout invasion is present and likely to occur. To address the dietary component, I employed stable isotope analysis to investigate how Brook Trout and Brown Trout interact with the dietary niche of Bull Trout. I determined that Bull Trout in sympatry with both Brook Trout and Brown Trout undergo a niche shift and are displaced from terrestrial-based resources. Furthermore, potential for competitive exclusion exists when resources are low given all species exhibit a high degree of niche overlap ( > 80%) when in sympatry and the amount of niche overlap does not decrease between allopatry and sympatry. The findings of my thesis suggest that both Brook Trout and Brown Trout interfere with the resource use of Bull Trout, on multiple levels, and provides practical guidelines for limiting future declines.

Native salmonid populations in the inland West are often restricted to small isolated habitats at risk from invasion by nonnative salmonids. However, further isolating these populations using barriers to prevent invasions can increase their extinction risk. This monograph reviews the state of knowledge about this tradeoff between invasion and isolation. We present a conceptual framework to guide analysis, focusing on four main questions concerning conservation value, vulnerability to invasion, persistence given isolation, and priorities when conserving multiple populations. Two examples illustrate use of the framework, and a final section discusses opportunities for making strategic decisions when faced with the invasion-isolation tradeoff.

The purpose of this study is to document the seasonal distribution of adult/sub-adult bull trout (Salvelinus confluentus) in the Malheur River basin. Due to the decline of bull trout in the Columbia Basin, the United States Fish and Wildlife Service listed bull trout as a threatened species in June 1998. Past land management activities; construction of dams; and fish eradication projects in the North Fork and Middle Fork Malheur River by poisoning have worked in concert to cumulatively impact native species in the Malheur Basin (Bowers et. al. 1993). Survival of the remaining bull trout populations is severely threatened (Buchanan 1997). 1999 Research Objects are: (1) Document the migratory patterns of adult/sub-adult bull trout in the North Fork Malheur River; (2) Determine the seasonal bull trout use of Beulah Reservoir and bull trout entrainment; and (3) Timing and location of bull trout spawning in the North Fork Malheur River basin. The study area includes the Malheur basin from the mouth of the Malheur River located near Ontario, Oregon to the headwaters of the North Fork Malheur River (Map 1). All fish collected and most of the telemetry effort was done on the North Fork Malheur River subbasin (Map 2). Fish collection was conducted on the North Fork Malheur River at the tailwaters of Beulah Reservoir (RK 29), Beulah Reservoir (RK 29-RK 33), and in the North Fork Malheur River at Crane Crossing (RK 69) to the headwaters of the North Fork Malheur. Radio telemetry was done from the mouth of the Malheur River in Ontario, Oregon to the headwaters of the North Fork Malheur. This report will reflect all migration data collected from 3/1/99 to 12/31/99.

"Bull trout (Salvelinus confluentus) are native to many tributaries of the Snake River in southeast Washington. The Washington Department of Wildlife (WOW) and the American Fisheries Society (AFS) have dentified bull trout as a species of special concern which means that they may become threatened or endangered by relatively minor disturbances to their habitat (Williams et al.1989). Steelhead trout/rainbow trout (Oncorhynchus mykiss) and spring chinook salmon (O. tshawytscha) are also native to several tributaries of the Snake River in southeast Washington. These species of migratory fishes are depressed, partially due to the construction of several dams on the lower Snake River. In response to decreased run size, large hatchery programs were initiated to produce juvenile steelhead and salmon to supplement repressed tributary stocks, a practice known as supplementation. There is a concern that supplementing streams with artificially high numbers of steelhead and salmon may have an impact on resident bull trout in these streams. Historically, these three species of fish existed together in large numbers, however, the amount of high-quality habitat necessary for reproduction and rearing has been severely reduced in recent years, as compared to historic amounts. The findings of the first year of a two year study aimed at identifying species interactions in southeast Washington streams are presented in this report. Data was collected to assess population dynamics, habitat utilization and preference, feeding habits, fish movement and migration, age, condition, growth, and the spawning requirements of bull trout in each of four streams. A comparison of the indices was then made between the study streams to determine if bull trout differ in the presence of the putative competitor species. Bull trout populations were highest in the Tucannon River (supplemented stream), followed by Mill Creek (unsupplemented stream). Young of the year bull trout utilized riffle and cascade habitat the most in all four streams. Juvenile bull trout utilized scour pool and run habitat the most in all four streams. YOY bull trout preferred plunge pool and scour pool habitat, as did juvenile bull trout in all four streams. These data show that while in the presence of the putative competitors, bull trout prefer the same habitat as in the absence of the putative competitors. Juvenile bull trout preferred mayflies and stoneflies in Mill Creek, while in the presence of the competitor species they preferred caddisflies, stoneflies, and Oligochaeta. It is felt that this difference is due to the differences in food items available and not species interactions; bull trout consume what is present. Adult bull trout were difficult to capture, and therefore it was difficult to determine the migratory habits in the Tucannon River. It is recommended that future studies use radio telemetry to determine the migratory habitat of these fish. The age, condition, and growth rates of bull trout differed only minimally between streams, indicating that if competitive interactions are occurring between these species it is not reflected by: 1) The length at age of bull trout; 2) The length-weight relationship of bull trout; or, 3) The rate of growth of bull trout. The spawning habits of bull trout and spring chinook salmon are similar in the Tucannon River, however it was found that they spawn in different river locations. The salmon spawn below river kilometer 83, while 82% of bull trout spawn above that point. The peak of spawning for salmon occurred 10 days before the peak of bull trout spawning, indicating that very little competition for spawning locations occurs between these species in the Tucannon River. Future species interactions study recommendations include the use of electrofishing to enumerate bull trout populations, snorkeling to identify micro-habitat utilization, seasonal diet analysis, and radio transmitters to identify seasonal migration patterns of bull trout"--Document.

The Malheur River is a 306-kilometer tributary to the Snake River, which drains 12,950 square kilometers. The Malheur River originates in the Blue Mountains and flows into the Snake River near Ontario, Oregon. The climate of the basin is characterized by hot dry summers, occasionally exceeding 38 C, and cold winters that may drop below -29 C. Average annual precipitation is 30 centimeters in the lower reaches. Wooded areas consist primarily of mixed fir and pine forest in the higher elevations. Sagebrush and grass communities dominate the flora in the lower elevations. Efforts to document salmonid life histories, water quality, and habitat conditions have continued in fiscal year 2002. Bull trout Salvelinus confluentus are considered to be cold water species and are temperature-dependant. Due to the interest of bull trout from various state and Federal agencies, a workgroup was formed to develop project objectives related to bull trout. Table 1 lists individuals that participated in the 2002 work group. This report will reflect work completed during the Bonneville Power Administration contract period starting April 1, 2002, and ending March 31, 2003. All tasks were conducted within this timeframe, and a more detailed timeframe may be referred to in each individual report.

"The goal of this two year study was to determine if supplementation with hatchery reared steelhead trout (Oncorhynchus mykiss) and spring chinook salmon (0. tshawytscha) negatively impacted wild native bull trout (Salvelinus confluentus) through competitive interactions. Four streams with varying levels of supplementation activity were sampled in Southeast Washington: Mill Creek, Tucannon River, Wolf Fork and Asotin Creek. Mill Creek was not supplemented with hatchery reared fish. The Tucannon River was intensely supplemented with hatchery reared steelhead smolts, rainbow trout and spring chinook salmon smolts. Wolf Fork was indirectly supplemented with hatchery reared steelhead smolts by releasing smolts at the mouth of the stream. Asotin Creek was supplemented for three years in the mid-1980's with hatchery reared steelhead smolts. Sampling in Asotin Creek was discontinued after the first year of study because too few bull trout were collected for analysis (n = 1). Tasks performed during this study were population density, relative abundance, microhabitat utilization, habitat availability, diet analysis, bull trout spawning ground surveys, radio telemetry of adult bull trout, and growth analysis. The data were used to identify the extent of geographic overlap among species and resources utilized by each species. This information was compared among stream populations and among species within a stream to identify changes in behavior that resulted from supplementation activities. We found that bull trout overlapped geographically with the supplemented species in each of the study streams suggesting competition among species was possible. Within a stream, bull trout and the supplemented species utilized dissimilar microhabitats. Among streams, microhabitat utilization by species was similar suggesting that supplementation activities had not resulted in a shift in habitat utilization. The diet of bull trout and O. mykiss significantly overlapped in each of the study streams, however, food was abundant and did not appear to be a limited resource. Age at length and back- calculated lengths identified differences in growth among bull trout and steelhead populations. The stream most intensely supplemented contained bull trout with the slowest growth and the non-supplemented stream contained bull trout with the fastest growth. Conversely, the stream most intensely supplemented contain O. myksis with the fastest growth and the non-supplemented stream contained O. mykisis with the slowest growth. Growth indicated that bull trout may have been negatively impacted from supplementation, although, other factors such as stream temperature may have contributed to the difference in growth. Condition factor among stream populations did not differ suggesting that the ability of each fish species to add weight as length increased was the same among stream populations. At current population levels, and current habitat quantity and quality, I detected no impacts to bull trout as a result of supplementation with hatchery reared O. mykiss trout and spring chinook salmon"--Document.