Download or read book Relationships Between Relative Abundance of Resident Bull Trout Salvelinus Confluentus and Habitat Characteristics in Central Idaho Mountain Streams written by Caleb Frederick Zurstadt and published by . This book was released on 2000 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: Resident bull trout (Salvelinus confluentus) may be particularly vulnerable to human related disturbance, however very few studies have focused on resident bull trout populations. The abundance of bull trout is one measure of the strength and potential for persistence of a population. Habitat characteristics may influence resident bull trout abundance to differing degrees and by varying means at multiple spatial scales. We used day and night snorkel counts to assess relative bull trout abundance. A modification of the Forest Service R1/R4 Fish and Fish Habitat Inventory was used to assess habitat characteristics associated with resident bull trout. Logistic and multiple linear regression were used to assess the relationships between resident bull trout abundance and habitat characteristics at the patch (1 to 5 km), reach (0.5 to 1 km) and habitat unit (1 to 100 m) scales. Site categorical variables were used along with quantitative habitat variables to explain among-site and across-site variation in the data. The significance of both quantitative habitat variables and categorical site variables at various spatial scales suggest that relationships between bull trout abundance and habitat characteristics are complex and in part dependent on scale. The characteristics of individual habitat units explained little of the variation in bull trout presence/absence (logistic regression; Somers' D=0.44) and density (multiple linear regression; adjusted R2=0.08) in habitat units, however there were habitat characteristics that were significantly (P≤0.05) correlated to bull trout presence/absence and density in habitat units. The relationships between habitat characteristics and bull trout presence/absence and density varied between habitat unit types. There was a strong quadratic relationship between bull trout abundance and mean summer water temperature at the reach (P=0.004) and patch scales (P=0.001). The mean temperature of patches appears to explain some of the variation in bull trout density at smaller spatial scales, such as reaches and habitat units. An appreciation of the complex nature of scale dependent interactions between bull trout abundance and habitat characteristics may help resource managers make wiser decisions regarding conservation of resident bull trout populations.
Download or read book Demographic and Habitat Requirements for Conservation of Bull Trout written by Bruce E. Rieman and published by . This book was released on 1993 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Watershed scale Monitoring Protocol for Bull Trout written by Dan Isaak and published by . This book was released on 2009 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Influence of Abiotic and Biotic Factors on Occurrence of Resident Bull Trout in Fragmented Habitats Western Montana written by Cecil Frank Rich and published by . This book was released on 1996 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Assessing the Effects of Non native Salmonids on Bull Trout Salvelinus Confluentus in Alberta s Rocky Mountain Foothills written by Jacqueline L. Pallard and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Bull Trout Distribution and Abundance in the Waters on and Bordering the Warm Springs Reservation written by and published by . This book was released on 2003 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: The range of bull trout (Salvelinus confluentus) in the Deschutes River basin has decreased from historic levels due to many factors including dam construction, habitat degradation, brook trout introduction and eradication efforts. While the bull trout population appears to be healthy in the Metolius River-Lake Billy Chinook system they have been largely extirpated from the upper Deschutes River (Buchanan et al. 1997). Little was known about bull trout in the lower Deschutes basin until BPA funded project No. 9405400 began during 1998. In this progress report we describe the findings to date from this multi-year study aimed at determining the life history, habitat needs and limiting factors of bull trout in the lower Deschutes subbasin. Juvenile bull trout and brook trout (Salvelinus fontinalis) relative abundance has been assessed in the Warm Springs River and Shitike Creek since 1999. In the Warm Springs R. the relative densities of juvenile bull trout and brook trout were .003 fish/m2 and .001 fish/m2 respectively during 2002. These densities were the lowest recorded in the Warm Springs River during the period of study. In Shitike Cr. the relative densities of juvenile bull trout and brook trout were .025 fish/m2 and .01 fish/m2 respectively during 2002. The utility of using index reaches to monitor trends in juvenile bull trout and brook trout relative abundance in the Warm Springs R. has been assessed since 1999. During 2002 the mean relative densities of juvenile bull trout within the 2.4 km study area was higher than what was observed in four index reaches. However, the mean relative densities of brook trout was slightly higher in the index reaches than what was observed in the 2.4 km study area. Habitat use by both juvenile bull trout and brook trout was determined in the Warm Springs R. Juvenile bull trout and brook trout were most abundant in pools and glides. However pools and glides comprised less than 20% of the available habitat in the study area during 2002. Multiple-pass spawning ground surveys were conducted during late August through October in the Warm Springs R. and Shitike Cr. during 2002. One-hundred and thirteen (113) redds were enumerated in the Warm Springs R. and 204 redds were found in Shitike Cr. The number of redds enumerated in both the Warm Springs R. and Shitike Cr. were the most redds observed since surveys began in 1998. Spatial and temporal distribution in spawning within the Warm Springs R. and Shitike Cr. is discussed. Juvenile emigration has been monitored in Shitike Creek since 1996. A total of 312 juveniles were estimated to have emigrated from Shitike Cr. during the spring, 2002. Adult escapement was monitored in the Warm Springs R. and Shitike Cr. Thirty adults were recorded at the Warm Springs National Fish Hatchery weir during 2002. This was the highest number of spawning adults recorded to date. A weir equipped with an underwater video camera near the spawning grounds was operated in the Warm Springs R. Thirty-one adults were recorded at the weir in day counts. The adult trap in Shitike Cr. was unsuccessful in capturing adult bull trout during 2002 due to damage from a spring high water event. Thermographs were placed throughout Warm Springs R. and Shitike Cr. to monitor water temperatures during bull trout migration, holding and spawning/rearing periods. During 1999-2002 water temperatures ranged from 11.8-15.4 C near the mouths during adult migration; 11.4-14.6 C during pre-spawning holding; and 6.5-8.4 C during adult spawning and juvenile rearing.
Download or read book Factors Influencing Spawning Migration of Bull Trout Salvelinus Confluentus in the North Fork Skokomish River Olympic National Park Washington written by Samuel J. Brenkman and published by . This book was released on 1998 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: Distribution and life history characteristics of lacustrine-adfluvial bull trout (Salvelinus confluentus) were described in the North Fork Skokomish River Basin (including Lake Cushman, a reservoir) from 1994 to 1996. Day snorkeling was conducted in the river to determine initiation of the bull trout spawning migration, abundance of spawners, and duration of spawning. Declining photoperiod, increased river discharge, and decreased water temperature appeared to influence timing of migration and spawning. Lacustrine-adfluvial bull trout typically entered the North Fork Skokomish River in October although some fish entered as early as May. Mean lengths of spawners consistently increased from June to December 1996, and early migrating bull trout were shorter than those fish that entered after river discharge increased in October. The presence of two phases of the spawning migration may be indicative of two populations spawning in the river. Bull trout spawned between mid-September and December in the river and tributaries after water temperatures declined. All spawning occurred at temperatures less than 7.5°C. Comparisons with studies of other lacustrine-adfiuvial bull trout populations that inhabit river and reservoir complexes suggested that bull trout exhibit specific migratory strategies related to local environmental conditions. In the North Fork Skokomish River, changes in abundance of bull trout, mountain whitefish (Prosopium wilhamsom), cutthroat trout (Oncorhynchus dark), and rainbow trout (Oncorhynchus mykiss) revealed distinct temporal segregation among these species. Olympic National Park, a designated Biosphere Reserve, contains one of the largest remaining areas of relatively pristine habitat in the range of bull trout. Knowledge of responses of bull trout to changes in river discharge and temperature from relatively undisturbed systems, such as the North Fork Skokomish River, may be useful in understanding patterns observed in degraded environments.
Download or read book Distribution and Movement of Bull Trout in the Upper Jarbidge River Watershed Nevada written by U.S. Department of the Interior and published by CreateSpace. This book was released on 2014-03-30 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: In 2006 and 2007, we surveyed the occurrence of bull trout (Salvelinus confluentus), the relative distributions of bull trout and redband trout (Oncorhynchus mykiss), and stream habitat conditions in the East and West Forks of the Jarbidge River in northeastern Nevada and southern Idaho. We installed passive integrated transponder (PIT) tag interrogation systems at strategic locations within the watershed, and PIT-tagged bull trout were monitored to evaluate individual fish growth, movement, and the connectivity of bull trout between streams. Robust bull trout populations were found in the upper portions of the East Fork Jarbidge River, the West Fork Jarbidge River, and in the Pine, Jack, Dave, and Fall Creeks. Small numbers of bull trout also were found in Slide and Cougar Creeks. Bull trout were numerically dominant in the upper portions of the East Fork Jarbidge River, and in Fall, Dave, Jack, and Pine Creeks, whereas redband trout were numerically dominant throughout the rest of the watershed. The relative abundance of bull trout was notably higher at altitudes above 2,100 m.
Download or read book Age Structure Growth and Factors Affecting Relative Abundance of Life History Forms of Bull Trout in the Clark Fork River Drainage Montana and Idaho written by Nikolas Dainus Zymonas and published by . This book was released on 2006 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: However, obtaining adequate fin ray samples for large fish (>400 mm TL) proved difficult and additional work is needed to validate age and growth estimation procedures. Third, I analyzed age and growth of bull trout in relation to environmental conditions in study streams. Bull trout in predominantly migratory populations held lower proportions of individuals> age 3 during summer and generally displayed higher growth rates during ages 0 and 1 than those in resident populations. Migratory populations exhibited overall faster early growth, although not in all cases. Age-0 growth was positively associated with length of growing season, whereas age-1 growth was negatively associated with density of bull trout and positively related to presence of nonnative salmonids. Presence of the migratory life history was influenced by severity of barriers to migration and presence of nonnative brook and brown trout. These results suggest that the migratory life history may be encouraged by enhancing migratory corridors and juvenile rearing habitat in lower reaches of tributaries.
Download or read book Bull Trout Recovery Under the Endangered Species Act written by United States. Congress. Senate. Committee on Environment and Public Works. Subcommittee on Fisheries, Wildlife, and Water and published by . This book was released on 2004 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bull Trout Salvelinus Confluentus Movement in Relation to Water Temperature Season and Habitat Features in Arrowrock Reservoir Idaho 2012 written by Terry R. Maret and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bull Trout Distribution and Abundance in the Waters on and Bordering the Warm Springs Indian Reservation 2001 Annual Report written by and published by . This book was released on 2002 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt: The range of bull trout (Salvelinus confluentus) in the Deschutes River basin has decreased from historic levels due to many factors including dam construction, habitat degradation, brook trout introduction and eradication efforts. While the bull trout population appears to be stable in the Metolius River-Lake Billy Chinook system they have been largely extirpated from the upper Deschutes River (Buchanan et al. 1997). Little was known about bull trout in the lower Deschutes basin until BPA funded project No. 9405400 began during 1998. In this progress report we describe the findings from the fourth year (2001) of the multi-year study aimed at determining the life history, habitat needs and limiting factors of bull trout in the lower Deschutes subbasin. Juvenile bull trout and brook trout (Salvelinus fontinalis) relative abundance was assessed in the Warm Springs River and Shitike Creek by night snorkeling. In the Warm Springs R. juvenile bull trout were slightly more numerous than brook trout, however, both were found in low densities. Relative densities of both species were the lowest observed since surveys began in 1999. Relative densities of juvenile bull trout and brook trout increased in Shitike Cr. Juvenile bull trout vastly out numbered brook trout in Shitike Cr. The utility of using index reaches to monitor trends in juvenile bull trout and brook trout relative abundance was assessed in the Warm Springs R. for the third year. Mean relative densities of juvenile bull trout within the index reaches was slightly higher than what was observed in the 2.4 km control reach. However, the mean relative density of brook trout in the 2.4 km control reach was slightly higher than what was observed in within the index reaches. Habitat use by both juvenile bull trout and brook trout was determined in the Warm Springs R. Juvenile bull trout and brook trout occupied pools more frequently than glides, riffles and rapids. However, pools accounted for only a small percentage of the total habitat. Multiple pass spawning ground surveys were conducted during late August through October in the Warm Springs R. and Shitike Cr. The number of redds enumerated in the Warm Springs R. declined substantially from 1998-2000 observations. Total redds recorded in Shitike Cr. was higher than 2000, but fewer than observed in 1998-1999. Spatial and temporal distribution in spawning within Warm Springs R. and Shitike Cr. is discussed. Juvenile emigration was monitored in Shitike Cr. The number of emigrants was the highest recorded since 1996. As in past years both a spring and fall migration period was observed. Adult escapement was monitored in the Warm Spring R. and Shitike Cr. The number of adults recorded passing the Warm Springs National Fish Hatchery weir was the second highest recorded since 1995. An adult trap was successfully operated in Shitike Cr. Eighty adult bull trout were enumerated during 2001.
Download or read book Bull Trout Distribution and Abundance in the Waters on and Bordering the Warm Springs Indian Reservation 2000 Annual Report written by and published by . This book was released on 2000 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: The range of bull trout (Salvelinus confluentus) in the Deschutes River basin has decreased from historic levels due to many factors including dam construction, habitat degradation, brook trout introduction and eradication efforts. While the bull trout population appears to be stable in the Metolius River-Lake Billy Chinook system they have been largely extirpated from the upper Deschutes River (Buchanan et al. 1997). Little was known about bull trout in the lower Deschutes basin until BPA funded project No. 9405400 began during 1998. In this progress report we describe the findings from the third year (2000) of the multi-year study aimed at determining the life history, genetics, habitat needs and limiting factors of bull trout in the lower Deschutes subbasin. Juvenile bull trout and brook trout (Salvelinus fontinalis) relative abundance was assessed in the Warm Springs River and Shitike Creek by night snorkeling. In the Warm Springs R. juvenile bull trout were slightly more numerous than brook trout, however, both were found in low densities. Relative densities of both species declined from 1999 observations. Juvenile bull trout vastly out numbered brook trout in Shitike Cr. Relative densities of juvenile bull trout increased while brook trout abundance was similar to 1999 observations in eight index reaches. The utility of using index reaches to monitor trends in juvenile bull trout and brook trout relative abundance was assessed in the Warm Springs R. for the second year. Mean relative densities of both species, within the index reaches was slightly higher than what was observed in a 2.4 km control reach. Mill Creek was surveyed for the presence of juvenile bull trout. The American Fisheries Society ''Interim protocol for determining bull trout presence'' methodology was field tested. No bull trout were found in the 2 km survey area.
Download or read book Investigations of Bull Trout Salvelinus Confluentus Steelhead Trout Oncorhynchus Mykiss and Spring Chinook Salmon O Tshawytscha Interactions in Southeast Washington Streams written by Steven W. Martin and published by . This book was released on 1992 with total page 570 pages. Available in PDF, EPUB and Kindle. Book excerpt: "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.
Download or read book Distribution and Habitat Use of Bull Trout Following the Removal of Nonnative Brook Trout written by Dirk Renner and published by . This book was released on 2005 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Invasion by nonnative brook trout (Salvelinus fontinalis) often results in replacement of bull trout (Salvelinus confluentus) in western North America, but the causal mechanisms are not well understood. Removal of brook trout from 1992 to 2000 from Sun Creek in southern Oregon, provided an opportunity to investigate the changes in distribution and abundance of bull trout. This study investigated bull trout distribution over from 1994 to 2003, during and following the extirpation of brook trout in 2000. In 2001 over, 8 km of contiguous stream habitat was examined to investigate bull trout habitat utilization. Bull trout abundance increased almost 300% after the removal of brook trout; however, bull trout distribution did not shift either upstream or downstream into habitat previously occupied by brook trout. This finding suggested that the occupied habitat was either critical for bull trout persistence or that factors restricted dispersal. Temperature did not appear to limit bull trout distribution remaining below 17°C with averages less than 10°C throughout Sun Creek. The downstream distribution of bull trout coincided with a point source increase of turbidity. In regions of the stream where turbidity was low bull trout abundance was positively associated with deep pools, higher average temperatures, and correlated with high densities of springs. The results of this study suggest that brook trout did not displace bull trout, underscoring the importance that point source disturbances (i.e. turbidity) can have on trout distributions. These findings reiterate the value of sampling contiguous streams as a means to identifying factors influencing trout distribution throughout a stream system.
Download or read book Investigations of Bull Trout Salvelinus Confluentus Steelhead Trout Oncorhynchus Mykiss and Spring Chinook Salmon O Tshawytscha Interactions in Southeast Washington Streams written by Keith D. Underwood and published by . This book was released on 1995 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt: "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.
Download or read book Investigations of Bull Trout Salvelinus Confluentus Steelhead Trout Oncorhynchus Mykiss and Spring Chinook Salmon O Tshawytscha Interactions in Southeast Washington Streams written by and published by . This book was released on 1992 with total page 219 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bull trout (Salvelinus confluentus) are native to many tributaries of the Snake River in southeast Washington. The Washington Department of Wildlife (WDW) and the American Fisheries Society (AFS) have identified bull trout as a species of special concern which means that they may become threatened or endangered by relatively, minor disturbances to their habitat. 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 program 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.
