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• 1. [Article] Feeding behavior and diet of native bull trout Salvelinus confluentus and introduced brook trout S. fontinalis in two Eastern Oregon streams

  One of the greatest threats to native bull trout Salvelinus confluentus populations is the presence of non-native brook trout S. fontinalis. This study, conducted in two second-order Eastern Oregon streams, ...

  Citation × Citation Citation Abstract Copy Title: Feeding behavior and diet of native bull trout Salvelinus confluentus and introduced brook trout S. fontinalis in two Eastern Oregon streams Author: Gunckel, Stephanie L. One of the greatest threats to native bull trout Salvelinus confluentus populations is the presence of non-native brook trout S. fontinalis. This study, conducted in two second-order Eastern Oregon streams, investigates the effect of brook trout on the feeding behavior arid diet of bull trout. Feeding behavior, microhabitat use, and agonistic interactions were examined in a controlled in-stream experiment where twenty enclosures were randomly assigned one of three treatments: two bull trout, four bull trout, or a mix of two bull trout and two brook trout. Results provide little evidence of a niche shift for bull trout in the presence of brook trout or of resource partitioning between sympatric bull trout and brook trout. All fish held focal feeding points in similar microhabitats and fed primarily from the water column. Brook trout showed the greatest growth, were highly aggressive, and consistently dominated bull trout of equal size. Examination of stomach contents revealed allopatric bull trout, sympatric bull and brook trout fed primarily on larvae of Ephemeroptera, Trichoptera, and aquatic Diptera and terrestrial insects. Sympatric bull trout and brook trout had a high degree of dietary overlap. All fish exhibited size selective predation, and piscivory was rare. Similar habitat use, feeding behavior and diet of bull trout and brook trout, and aggressive interactions between these species suggest that, when habitat and prey resources are scarce, direct interference competition is likely, and the dominant behavior of brook trout may potentially displace bull trout. Title: Feeding behavior and diet of native bull trout Salvelinus confluentus and introduced brook trout S. fontinalis in two Eastern Oregon streams Author: Gunckel, Stephanie L. One of the greatest threats to native bull trout Salvelinus confluentus populations is the presence of non-native brook trout S. fontinalis. This study, conducted in two second-order Eastern Oregon streams, investigates the effect of brook trout on the feeding behavior arid diet of bull trout. Feeding behavior, microhabitat use, and agonistic interactions were examined in a controlled in-stream experiment where twenty enclosures were randomly assigned one of three treatments: two bull trout, four bull trout, or a mix of two bull trout and two brook trout. Results provide little evidence of a niche shift for bull trout in the presence of brook trout or of resource partitioning between sympatric bull trout and brook trout. All fish held focal feeding points in similar microhabitats and fed primarily from the water column. Brook trout showed the greatest growth, were highly aggressive, and consistently dominated bull trout of equal size. Examination of stomach contents revealed allopatric bull trout, sympatric bull and brook trout fed primarily on larvae of Ephemeroptera, Trichoptera, and aquatic Diptera and terrestrial insects. Sympatric bull trout and brook trout had a high degree of dietary overlap. All fish exhibited size selective predation, and piscivory was rare. Similar habitat use, feeding behavior and diet of bull trout and brook trout, and aggressive interactions between these species suggest that, when habitat and prey resources are scarce, direct interference competition is likely, and the dominant behavior of brook trout may potentially displace bull trout. Close

• 2. [Article] Distribution and habitat use of bull trout following the removal of nonnative brook trout

  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. ...

  Citation × Citation Citation Abstract Copy Title: Distribution and habitat use of bull trout following the removal of nonnative brook trout Author: Renner, Dirk 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. Title: Distribution and habitat use of bull trout following the removal of nonnative brook trout Author: Renner, Dirk 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. Close

• 3. [Article] Catch, Migration, Growth and Survival of Stocked Coastal Cutthroat Trout in Munsel Lake, Oregon

  The latest phase of a study of the migration, survival, growth, and catch of coastal cutthroat trout, conducted to compare cutthroat trout and rainbow trout. The document describes the geological and biological ...

  Citation × Citation Citation Abstract Copy Title: Catch, Migration, Growth and Survival of Stocked Coastal Cutthroat Trout in Munsel Lake, Oregon Author: Oregon State Game Commission, Skeesick, Delbert G. The latest phase of a study of the migration, survival, growth, and catch of coastal cutthroat trout, conducted to compare cutthroat trout and rainbow trout. The document describes the geological and biological characteristics of Munsel Creek weir, where the studies were conducted. It also includes graphs of the data and a summary of the results. Title: Catch, Migration, Growth and Survival of Stocked Coastal Cutthroat Trout in Munsel Lake, Oregon Author: Oregon State Game Commission, Skeesick, Delbert G. The latest phase of a study of the migration, survival, growth, and catch of coastal cutthroat trout, conducted to compare cutthroat trout and rainbow trout. The document describes the geological and biological characteristics of Munsel Creek weir, where the studies were conducted. It also includes graphs of the data and a summary of the results. Close

• 4. [Article] Factors influencing spawning migration of bull trout (Salvelinus confluentus) in the North Fork Skokomish River, Olympic National Park, Washington

  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 ...

  Citation × Citation Citation Abstract Copy Title: Factors influencing spawning migration of bull trout (Salvelinus confluentus) in the North Fork Skokomish River, Olympic National Park, Washington Author: Brenkman, Samuel J. 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. Title: Factors influencing spawning migration of bull trout (Salvelinus confluentus) in the North Fork Skokomish River, Olympic National Park, Washington Author: Brenkman, Samuel J. 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. Close

• 5. [Article] Bull Trout (Salvelinus confluentus) Population and Habitat Survey in the McKenzie and Middle Fork Willamette Basins, 2001

  Our study area includes the three McKenzie populations, and a reintroduced population in the Middle Fork Willamette and tributaries above Hills Creek Reservoir. We monitored bull trout populations in the ...

  Citation × Citation Citation Abstract Copy Title: Bull Trout (Salvelinus confluentus) Population and Habitat Survey in the McKenzie and Middle Fork Willamette Basins, 2001 Author: Taylor, Greg Our study area includes the three McKenzie populations, and a reintroduced population in the Middle Fork Willamette and tributaries above Hills Creek Reservoir. We monitored bull trout populations in the McKenzie and Middle Fork Willamette basins using a combination of sampling techniques that include spawning surveys, juvenile trapping, electronic fish counters, and night snorkeling. We continued to reintroduce bull trout fry from Anderson Creek (McKenzie Basin) to the Middle Fork Willamette above Hills Creek Reservoir in an attempt to rehabilitate the bull trout population in the Middle Fork Willamette Basin. By monitoring population trends and determining life history characteristics of bull trout in McKenzie and Middle Fork Willamette basins, we can make informed management decisions that will help maintain long term and sustainable bull trout populations in the upper Willamette Basin. Title: Bull Trout (Salvelinus confluentus) Population and Habitat Survey in the McKenzie and Middle Fork Willamette Basins, 2001 Author: Taylor, Greg Our study area includes the three McKenzie populations, and a reintroduced population in the Middle Fork Willamette and tributaries above Hills Creek Reservoir. We monitored bull trout populations in the McKenzie and Middle Fork Willamette basins using a combination of sampling techniques that include spawning surveys, juvenile trapping, electronic fish counters, and night snorkeling. We continued to reintroduce bull trout fry from Anderson Creek (McKenzie Basin) to the Middle Fork Willamette above Hills Creek Reservoir in an attempt to rehabilitate the bull trout population in the Middle Fork Willamette Basin. By monitoring population trends and determining life history characteristics of bull trout in McKenzie and Middle Fork Willamette basins, we can make informed management decisions that will help maintain long term and sustainable bull trout populations in the upper Willamette Basin. Close

• 6. [Article] Stream habitat utilization and behavior of sympatric and allopatric wild cutthroat trout (Salmo clarki) and hatchery coho salmon (Oncorhynchus kitsutch)

  The behavior and stream habitat utilization of juvenile hatchery-reared coho salmon (Ovicozihynchus kisutch) and wild cutthroat trout (Salmo clarki) were examined to assess the nature of interactions between ...

  Citation × Citation Citation Abstract Copy Title: Stream habitat utilization and behavior of sympatric and allopatric wild cutthroat trout (Salmo clarki) and hatchery coho salmon (Oncorhynchus kitsutch) Author: Jacobs, Steven Edward The behavior and stream habitat utilization of juvenile hatchery-reared coho salmon (Ovicozihynchus kisutch) and wild cutthroat trout (Salmo clarki) were examined to assess the nature of interactions between the species potentially resulting from introductions of hatchery coho salmon in streams. Habitat utilization was monitored in Mill Creek, Polk Co., Oregon by manipulating the composition of fish within three study sections to include either allopatric or sympatric populations of hatchery coho salmon and wild cutthroat trout. In allopatry, coho salmon and cutthroat trout selected feeding microhabitat that was similar in physical characteristics and exhibited extensive dietary overlap. When the two species occurred in sympatry, feeding microhabitat used by coho salmon was altered, however, that of cutthroat trout was comparable to allopatric cutthroat trout. No discernable differences in dietary composition between allopatric and sympatric fish were detected. While allopatric cutthroat trout always gained mass. ailopatric coho salmon always lost mass. Stomach fullness indices were higher for allopatric cutthroat trout than allopatric coho salmon. Sympatric cutthroat trout had comparable or greater gains of mass, indices of stomach fullness, and hepatic glycogen reserves relative to allopatric cutthroat trout. Conversely, sympatric coho salmon had greater losses of mass, reduced hepatic glycogen reserves, and apparently lower indices of stomach fullness than allopatric salmon. Behavioral observations made through the use of an in-stream viewing chamber in Berry Creek, Benton Co., Oregon, indicated that in allopatry populations of hatchery coho salmon and wild cutthroat trout were structured as linear dominance hierarchies that were organized by quantitatively and qualitatively similar aggressive interactions. In sympatry, however, cutthroat trout were more aggressive and socially dominant to coho salmon. The shift in use of micro-habitat and reduction in habitat utilization effectiveness of hatchery coho salmon in the presence of cutthroat trout can, thus, be interpreted to occur as a result of interference competition mediated through interspecific aggression. Title: Stream habitat utilization and behavior of sympatric and allopatric wild cutthroat trout (Salmo clarki) and hatchery coho salmon (Oncorhynchus kitsutch) Author: Jacobs, Steven Edward The behavior and stream habitat utilization of juvenile hatchery-reared coho salmon (Ovicozihynchus kisutch) and wild cutthroat trout (Salmo clarki) were examined to assess the nature of interactions between the species potentially resulting from introductions of hatchery coho salmon in streams. Habitat utilization was monitored in Mill Creek, Polk Co., Oregon by manipulating the composition of fish within three study sections to include either allopatric or sympatric populations of hatchery coho salmon and wild cutthroat trout. In allopatry, coho salmon and cutthroat trout selected feeding microhabitat that was similar in physical characteristics and exhibited extensive dietary overlap. When the two species occurred in sympatry, feeding microhabitat used by coho salmon was altered, however, that of cutthroat trout was comparable to allopatric cutthroat trout. No discernable differences in dietary composition between allopatric and sympatric fish were detected. While allopatric cutthroat trout always gained mass. ailopatric coho salmon always lost mass. Stomach fullness indices were higher for allopatric cutthroat trout than allopatric coho salmon. Sympatric cutthroat trout had comparable or greater gains of mass, indices of stomach fullness, and hepatic glycogen reserves relative to allopatric cutthroat trout. Conversely, sympatric coho salmon had greater losses of mass, reduced hepatic glycogen reserves, and apparently lower indices of stomach fullness than allopatric salmon. Behavioral observations made through the use of an in-stream viewing chamber in Berry Creek, Benton Co., Oregon, indicated that in allopatry populations of hatchery coho salmon and wild cutthroat trout were structured as linear dominance hierarchies that were organized by quantitatively and qualitatively similar aggressive interactions. In sympatry, however, cutthroat trout were more aggressive and socially dominant to coho salmon. The shift in use of micro-habitat and reduction in habitat utilization effectiveness of hatchery coho salmon in the presence of cutthroat trout can, thus, be interpreted to occur as a result of interference competition mediated through interspecific aggression. Close

• 7. [Article] Experimental analysis of intra- and interspecific competitive interactions between cutthroat trout and sculpins in small streams

  In the Pacific Northwest ecoregion of North America, sculpins represent a major constituent of freshwater assemblages in coastal rivers. Based on their prevalence and abundance, sculpins are likely important ...

  Citation × Citation Citation Abstract Copy Title: Experimental analysis of intra- and interspecific competitive interactions between cutthroat trout and sculpins in small streams Author: Ramirez, Ben S. In the Pacific Northwest ecoregion of North America, sculpins represent a major constituent of freshwater assemblages in coastal rivers. Based on their prevalence and abundance, sculpins are likely important ecologically, yet little is known of their interactions with co-occurring species, such as widely studied salmon and trout (salmonines). In this study, I evaluated inter- and intraspecific interactions involving cottids (Cottus sp.) and coastal cutthroat trout (Oncorhynchus clarkii clarkii). I used a response surface experimental design to independently evaluate effects of cutthroat trout and sculpin biomass on growth and behavior. There was evidence of both intra- and interspecific interactions between cutthroat trout and sculpins, but the interactions were asymmetrical with biomass of cutthroat trout driving both intra- and interspecific interactions, whereas sculpins had little influence overall. Cutthroat trout biomass was positively related to conspecific aggressive interactions and negatively related to growth. Sculpin exhibited increased use of cover during the day in response to greater biomass of cutthroat trout, but not sculpin biomass. Nocturnal use of cover by sculpins was unaffected by biomass of either species. This experiment provides insights into the species interactions and the mechanisms that may allow sculpins and salmonines to coexist in nature. As cutthroat trout appear to be superior competitors, coexistence between sculpins and cutthroat trout may depend on some form of refuge, either in the form of in-stream cover or crypsis coupled with diel resource segregation. Cutthroat trout are usually active during the day, indicating that nocturnal foraging by sculpins may in part represent a behavior that minimizes interspecific competition with cutthroat trout. Title: Experimental analysis of intra- and interspecific competitive interactions between cutthroat trout and sculpins in small streams Author: Ramirez, Ben S. In the Pacific Northwest ecoregion of North America, sculpins represent a major constituent of freshwater assemblages in coastal rivers. Based on their prevalence and abundance, sculpins are likely important ecologically, yet little is known of their interactions with co-occurring species, such as widely studied salmon and trout (salmonines). In this study, I evaluated inter- and intraspecific interactions involving cottids (Cottus sp.) and coastal cutthroat trout (Oncorhynchus clarkii clarkii). I used a response surface experimental design to independently evaluate effects of cutthroat trout and sculpin biomass on growth and behavior. There was evidence of both intra- and interspecific interactions between cutthroat trout and sculpins, but the interactions were asymmetrical with biomass of cutthroat trout driving both intra- and interspecific interactions, whereas sculpins had little influence overall. Cutthroat trout biomass was positively related to conspecific aggressive interactions and negatively related to growth. Sculpin exhibited increased use of cover during the day in response to greater biomass of cutthroat trout, but not sculpin biomass. Nocturnal use of cover by sculpins was unaffected by biomass of either species. This experiment provides insights into the species interactions and the mechanisms that may allow sculpins and salmonines to coexist in nature. As cutthroat trout appear to be superior competitors, coexistence between sculpins and cutthroat trout may depend on some form of refuge, either in the form of in-stream cover or crypsis coupled with diel resource segregation. Cutthroat trout are usually active during the day, indicating that nocturnal foraging by sculpins may in part represent a behavior that minimizes interspecific competition with cutthroat trout. Close

• 8. [Article] Substitutional relationships between rainbow trout and pansize salmon : a market demand analysis

  The fundamental objective of this analysis was to isolate and identify the factors governing the demand for domestically produced rainbow trout in a representative west coast market, and assess the impact ...

  Citation × Citation Citation Abstract Copy Title: Substitutional relationships between rainbow trout and pansize salmon : a market demand analysis Author: Queirolo, Lewis E. The fundamental objective of this analysis was to isolate and identify the factors governing the demand for domestically produced rainbow trout in a representative west coast market, and assess the impact on that demand, if any, of the introduction of pansize salmon. The approach taken in this market demand study was to identify those variables hypothesized to determine supply and demand for rainbow trout. Several testable hypotheses concerning the anticipated relationships were specified. It was hypothesized that a negative relationship would exist between the price of trout at the brokerage level and the quantity demanded at that level. Conversely, the price of trout at the wholesale level was hypothesized to be positively correlated with the quantity of rainbow trout demanded at the brokerage level. Further, the signs on the coefficients of variables accounting for the wholesale prices of substitute items were expected to be negative, while comparable prices at the brokerage level should be positive, based upon the hypothesis. It was hypothesized that the presence of Japanese trout in the market place would have a negative impact on the quantity of domestically produced trout demanded. Personal disposable income was hypothesized to be positively correlated with the quantity of trout demanded. Expectations were that seasonal factors tend to cause trout demand to fluctuate cyclically. An econometric simultaneous equations model was specified from which estimates of the parameters of the demand equation were obtained using Two Stage Least Squares techniques. A recognition of the limitations associated with the available data set necessitates the emphasizing of the preliminary nature of these results. Data on quantities and prices of rainbow trout and equivalent price series for hypothesized substitutes were obtained through personal interviews with market participants and close observers thereof. The results of the study, while preliminary, tend to support the original set of hypotheses concerning the interrelationships between quantity of domestic trout demanded and own-price, the price of close substitutes and seasonal demand fluctuations. Somewhat unexpectedly, the regression seems to have uncovered a negative income/quantity demanded relationship for rainbow trout. This raises some interesting questions which might best be addressed in terms of hypotheses for future analysis. Title: Substitutional relationships between rainbow trout and pansize salmon : a market demand analysis Author: Queirolo, Lewis E. The fundamental objective of this analysis was to isolate and identify the factors governing the demand for domestically produced rainbow trout in a representative west coast market, and assess the impact on that demand, if any, of the introduction of pansize salmon. The approach taken in this market demand study was to identify those variables hypothesized to determine supply and demand for rainbow trout. Several testable hypotheses concerning the anticipated relationships were specified. It was hypothesized that a negative relationship would exist between the price of trout at the brokerage level and the quantity demanded at that level. Conversely, the price of trout at the wholesale level was hypothesized to be positively correlated with the quantity of rainbow trout demanded at the brokerage level. Further, the signs on the coefficients of variables accounting for the wholesale prices of substitute items were expected to be negative, while comparable prices at the brokerage level should be positive, based upon the hypothesis. It was hypothesized that the presence of Japanese trout in the market place would have a negative impact on the quantity of domestically produced trout demanded. Personal disposable income was hypothesized to be positively correlated with the quantity of trout demanded. Expectations were that seasonal factors tend to cause trout demand to fluctuate cyclically. An econometric simultaneous equations model was specified from which estimates of the parameters of the demand equation were obtained using Two Stage Least Squares techniques. A recognition of the limitations associated with the available data set necessitates the emphasizing of the preliminary nature of these results. Data on quantities and prices of rainbow trout and equivalent price series for hypothesized substitutes were obtained through personal interviews with market participants and close observers thereof. The results of the study, while preliminary, tend to support the original set of hypotheses concerning the interrelationships between quantity of domestic trout demanded and own-price, the price of close substitutes and seasonal demand fluctuations. Somewhat unexpectedly, the regression seems to have uncovered a negative income/quantity demanded relationship for rainbow trout. This raises some interesting questions which might best be addressed in terms of hypotheses for future analysis. Close

• 9. [Article] A genetic study of the red-band trout (Salmo sp.)

  A group of trout that reside in streams of the desiccating lake basins of southeastern Oregon differ markedly from other known Salmo. Known commonly as the red-band trout, this fish was subjected to chromosome ...

  Citation × Citation Citation Abstract Copy Title: A genetic study of the red-band trout (Salmo sp.) Author: Wilmot, Richard L. A group of trout that reside in streams of the desiccating lake basins of southeastern Oregon differ markedly from other known Salmo. Known commonly as the red-band trout, this fish was subjected to chromosome analysis for comparison with other species of western North American Salmo. The karyotype of the red-banded trout is 2n = 58 composed of 44 metacentrics, 2 metacentrics with satallites, 2 sub-metacentrics and 10 acrocentrics to give 104 chromosome arms. This karyotype is identical to that of the California golden trout, S. a.guabonita. A similar karyotype has been found, for trout from the Deschutes River and summer-run steelhead from the Siletz and Clearwater rivers. The chromosomal and distributional data is believed to indicate a widespread golden trout complex composed of the red-band trout, the California golden trout, and the Kern River trout inhabiting the Pacific Coast drainage from British Columbia to southern California. In the course of this study, a new karyotype was discovered for the Alvord cutthroat trout of 2n = 64 with 40 metacentrics and 24 acrocentrics to give 104 chromosome arms. Nineteen enzyme systems were analysed by starch-gel electrophoresis in two populations of the red-band trout. The Bridge Creek population displayed very low variability for only malate dehydroge, nase (MDH) and phosphoglucomutase (PGM). No variability was found in the Three-Mile Creek population. A new allele, not previously reported was found for MDH in the Bridge Creek population. The high degree of genetic similarity among and between these populations is thought to be the result of selection pressure rather than stochastic processes. The isolated populations of the red-banded trout appear to be well adapted to their present environment, but without the genetic variability to meet future environmental changes, they may face extinction. Their most immediate threat is man' s use of the environment. Title: A genetic study of the red-band trout (Salmo sp.) Author: Wilmot, Richard L. A group of trout that reside in streams of the desiccating lake basins of southeastern Oregon differ markedly from other known Salmo. Known commonly as the red-band trout, this fish was subjected to chromosome analysis for comparison with other species of western North American Salmo. The karyotype of the red-banded trout is 2n = 58 composed of 44 metacentrics, 2 metacentrics with satallites, 2 sub-metacentrics and 10 acrocentrics to give 104 chromosome arms. This karyotype is identical to that of the California golden trout, S. a.guabonita. A similar karyotype has been found, for trout from the Deschutes River and summer-run steelhead from the Siletz and Clearwater rivers. The chromosomal and distributional data is believed to indicate a widespread golden trout complex composed of the red-band trout, the California golden trout, and the Kern River trout inhabiting the Pacific Coast drainage from British Columbia to southern California. In the course of this study, a new karyotype was discovered for the Alvord cutthroat trout of 2n = 64 with 40 metacentrics and 24 acrocentrics to give 104 chromosome arms. Nineteen enzyme systems were analysed by starch-gel electrophoresis in two populations of the red-band trout. The Bridge Creek population displayed very low variability for only malate dehydroge, nase (MDH) and phosphoglucomutase (PGM). No variability was found in the Three-Mile Creek population. A new allele, not previously reported was found for MDH in the Bridge Creek population. The high degree of genetic similarity among and between these populations is thought to be the result of selection pressure rather than stochastic processes. The isolated populations of the red-banded trout appear to be well adapted to their present environment, but without the genetic variability to meet future environmental changes, they may face extinction. Their most immediate threat is man' s use of the environment. Close

• 10. [Article] Rainbow trout cystatin C : gene expression, heterologous production and characterization

  Rainbow trout cystatin C cDNA has been isolated from trout liver. The full-length cystatin cDNA (674 bp) included the 5'untranslated region and the polyadenylation signal sequence AATAAA in the 3' region. ...

  Citation × Citation Citation Abstract Copy Title: Rainbow trout cystatin C : gene expression, heterologous production and characterization Author: Li, Fugen Rainbow trout cystatin C cDNA has been isolated from trout liver. The full-length cystatin cDNA (674 bp) included the 5'untranslated region and the polyadenylation signal sequence AATAAA in the 3' region. Translation of the cDNA defines 132 amino acid residues. Comparison of the amino acid sequence with those of family 2 cystatins indicates that the 21 amino acids at the N-terminal end is a signal peptide necessary for cystatin secretion, and the remaining 111 amino acids represent mature cystatin. Four cysteine residues in the cystatin may form two disulfide bonds producing a molecule with the properties of a family 2 cystatin. Trout cystatin C gene expression was analyzed by Northern blot. This gene is expressed at various levels in all tissues examined. This difference may reflect differences in degree of regulation of cysteine proteinase activities. A high level of trout cystatin C expressed in trout hepatic tissue or cell cultures suggested that cystatin C expression might be related to tumorigenesis. Southern blot of trout genomic DNA showed that the copy number of the trout cystatin gene is probably one per haploid genome. Trout cystatin C was expressed in E. coli at a yield of 3-5 mg/L culture, but no inhibitory activity was detected for the untreated recombinant protein. However, after refolding, recombinant cystatin C displayed inhibitory activity against papain. The dissociation constant of recombinant cystatin C against papain is 1.2 x 10⁻⁶ nM, similar to that of human cystatin C. Trout cystatin C was also expressed in yeast cells, but no inhibitory activity was detected either. No cystatin C was secreted in the yeast expression system using either the trout cystatin C secretion signal, or the yeast invertase secretion signal. The expression levels of trout cystatin C in our expression systems are still low for industrial requirements. Therefore, further investigation will be needed to construct more efficient expression systems and vectors for trout cystatin C heterologous production. Title: Rainbow trout cystatin C : gene expression, heterologous production and characterization Author: Li, Fugen Rainbow trout cystatin C cDNA has been isolated from trout liver. The full-length cystatin cDNA (674 bp) included the 5'untranslated region and the polyadenylation signal sequence AATAAA in the 3' region. Translation of the cDNA defines 132 amino acid residues. Comparison of the amino acid sequence with those of family 2 cystatins indicates that the 21 amino acids at the N-terminal end is a signal peptide necessary for cystatin secretion, and the remaining 111 amino acids represent mature cystatin. Four cysteine residues in the cystatin may form two disulfide bonds producing a molecule with the properties of a family 2 cystatin. Trout cystatin C gene expression was analyzed by Northern blot. This gene is expressed at various levels in all tissues examined. This difference may reflect differences in degree of regulation of cysteine proteinase activities. A high level of trout cystatin C expressed in trout hepatic tissue or cell cultures suggested that cystatin C expression might be related to tumorigenesis. Southern blot of trout genomic DNA showed that the copy number of the trout cystatin gene is probably one per haploid genome. Trout cystatin C was expressed in E. coli at a yield of 3-5 mg/L culture, but no inhibitory activity was detected for the untreated recombinant protein. However, after refolding, recombinant cystatin C displayed inhibitory activity against papain. The dissociation constant of recombinant cystatin C against papain is 1.2 x 10⁻⁶ nM, similar to that of human cystatin C. Trout cystatin C was also expressed in yeast cells, but no inhibitory activity was detected either. No cystatin C was secreted in the yeast expression system using either the trout cystatin C secretion signal, or the yeast invertase secretion signal. The expression levels of trout cystatin C in our expression systems are still low for industrial requirements. Therefore, further investigation will be needed to construct more efficient expression systems and vectors for trout cystatin C heterologous production. Close

• 11. [Article] Characterization of a ras gene in rainbow trout

  The rainbow trout (Oncorhynchus mykiss) model of chemical carcinogenesis is becoming increasingly important as a supplement to rodent studies. However, much of the molecular biology of the carcinogenic response ...

  Citation × Citation Citation Abstract Copy Title: Characterization of a ras gene in rainbow trout Author: Mangold, Kathy A. The rainbow trout (Oncorhynchus mykiss) model of chemical carcinogenesis is becoming increasingly important as a supplement to rodent studies. However, much of the molecular biology of the carcinogenic response is still unknown in the trout model. The ras gene family has been implicated in the tumorigenesis of both spontaneous and chemically-induced tumors in mammals. This study is the first to characterize a ras proto-oncogene in rainbow trout. To accomplish this, the ras gene sequence was amplified in vitro by using polymerase chain reaction (PCR). Two synthetic and degenerative oligonucleotide sequences based on a consensus mammal/goldfish ras sequence were used as primers in the PCR procedure. An 800 base pair (bp) sequence was amplified from trout genomic DNA and hybridized with a human c-Ha-ras sequence. The initial amplifications of trout liver cDNA using the PCR procedure with the synthetic ras primers resulted in a single product of approximately 216 bps. However, this amplified "trout" 216 by product was subsequently shown to be an artifact of carryover from a human Ki-ras plasmid. Carryover is a common problem found in many laboratories involved with the PCR procedure, and extensive precautions were used to eliminate the problem in our laboratories. The 800 by PCR product was cloned and sequenced using Taq polymerase. RT-8, a clone containing the 800 bp insert, was shown to have 91% homology to the first two exons of mammalian c-Ha-ras gene and lesser homology to other ras genes. Amplification of trout liver cDNA using specific primers based on the RT-8 sequence resulted in the amplification of sequences identical to the sequence of the RT-8 insert without an intron, as well as unique sequences, which may represent additional trout ras genes. The PCR procedure was modified to identify sequence information immediately 3' of the known trout ras sequence. Partial sequences of at least two different trout ras genes are presented. With this new information, analysis of DNA sequence information from chemically initiated tumors may elucidate the role activation of ras genes plays in the trout model of carcinogenesis. Title: Characterization of a ras gene in rainbow trout Author: Mangold, Kathy A. The rainbow trout (Oncorhynchus mykiss) model of chemical carcinogenesis is becoming increasingly important as a supplement to rodent studies. However, much of the molecular biology of the carcinogenic response is still unknown in the trout model. The ras gene family has been implicated in the tumorigenesis of both spontaneous and chemically-induced tumors in mammals. This study is the first to characterize a ras proto-oncogene in rainbow trout. To accomplish this, the ras gene sequence was amplified in vitro by using polymerase chain reaction (PCR). Two synthetic and degenerative oligonucleotide sequences based on a consensus mammal/goldfish ras sequence were used as primers in the PCR procedure. An 800 base pair (bp) sequence was amplified from trout genomic DNA and hybridized with a human c-Ha-ras sequence. The initial amplifications of trout liver cDNA using the PCR procedure with the synthetic ras primers resulted in a single product of approximately 216 bps. However, this amplified "trout" 216 by product was subsequently shown to be an artifact of carryover from a human Ki-ras plasmid. Carryover is a common problem found in many laboratories involved with the PCR procedure, and extensive precautions were used to eliminate the problem in our laboratories. The 800 by PCR product was cloned and sequenced using Taq polymerase. RT-8, a clone containing the 800 bp insert, was shown to have 91% homology to the first two exons of mammalian c-Ha-ras gene and lesser homology to other ras genes. Amplification of trout liver cDNA using specific primers based on the RT-8 sequence resulted in the amplification of sequences identical to the sequence of the RT-8 insert without an intron, as well as unique sequences, which may represent additional trout ras genes. The PCR procedure was modified to identify sequence information immediately 3' of the known trout ras sequence. Partial sequences of at least two different trout ras genes are presented. With this new information, analysis of DNA sequence information from chemically initiated tumors may elucidate the role activation of ras genes plays in the trout model of carcinogenesis. Close

• 12. [Article] The feasibility of a consumptive wild trout sport fishery on the North Fork of the Middle Fork of the Willamette River

  The objective of this study was to determine whether wild populations of trout in the North Fork of the Middle Fork of the Willamette River can support a catch rate of 0.3-0.5 trout per hour at current ...

  Citation × Citation Citation Abstract Copy Title: The feasibility of a consumptive wild trout sport fishery on the North Fork of the Middle Fork of the Willamette River Author: Nicholas, Jay W. The objective of this study was to determine whether wild populations of trout in the North Fork of the Middle Fork of the Willamette River can support a catch rate of 0.3-0.5 trout per hour at current levels of effort and to predict how different size and bag limits would alter the number and ages of trout harvested. Angler use of the sport fishery in 1976 was estimated to be 2,730 angler days and 5,660 angler hours. The season average catch rate was 0.49 trout per hour. The number of trout counted in September 1975 and 1976 suggested that the trout populations had not declined between those two years. Rainbow trout are recruited to the fishery at about age II and 50% of the females are mature at age IV. Cutthroat trout are recruited to the fishery at about age III and 86% of the females are mature at that same age. Distribution of harvest among anglers and age specific lengths of native trout are used to demonstrate that size restrictions are the most effective means of selectively limiting trout harvest. The North Fork can continue to support a consumptive sport fishery with a catch rate of between 0.3 and 0.5 trout per hour at present levels of effort under the following assumptions: (1) angler use and harvest was similar in 1975 and 1976, (2) natural mortality was similar in both years, and (3) trout counts were not biased by unequal movement of fish into study pools in the second year. Title: The feasibility of a consumptive wild trout sport fishery on the North Fork of the Middle Fork of the Willamette River Author: Nicholas, Jay W. The objective of this study was to determine whether wild populations of trout in the North Fork of the Middle Fork of the Willamette River can support a catch rate of 0.3-0.5 trout per hour at current levels of effort and to predict how different size and bag limits would alter the number and ages of trout harvested. Angler use of the sport fishery in 1976 was estimated to be 2,730 angler days and 5,660 angler hours. The season average catch rate was 0.49 trout per hour. The number of trout counted in September 1975 and 1976 suggested that the trout populations had not declined between those two years. Rainbow trout are recruited to the fishery at about age II and 50% of the females are mature at age IV. Cutthroat trout are recruited to the fishery at about age III and 86% of the females are mature at that same age. Distribution of harvest among anglers and age specific lengths of native trout are used to demonstrate that size restrictions are the most effective means of selectively limiting trout harvest. The North Fork can continue to support a consumptive sport fishery with a catch rate of between 0.3 and 0.5 trout per hour at present levels of effort under the following assumptions: (1) angler use and harvest was similar in 1975 and 1976, (2) natural mortality was similar in both years, and (3) trout counts were not biased by unequal movement of fish into study pools in the second year. Close

• 13. [Article] Coexistence of top predators in headwater streams : pathways of intraguild predation between Pacific Giant salamander larvae and cutthroat trout

  The coexistence of multiple predators may have important consequences for the structure and function of communities. Interactions between predators may strongly affect their combined direct and indirect ...

  Citation × Citation Citation Abstract Copy Title: Coexistence of top predators in headwater streams : pathways of intraguild predation between Pacific Giant salamander larvae and cutthroat trout Author: Rundio, David E. The coexistence of multiple predators may have important consequences for the structure and function of communities. Interactions between predators may strongly affect their combined direct and indirect effects on prey populations and lower trophic levels. Predators often have size-structured populations, which may result in intraguild predation characterized by complex trophic and behavioral interactions. Coexistence of multiple predators may strongly depend on antipredator defenses of small size classes that reduce their vulnerability to predation. In Pacific Northwest forested ecosystems, Pacific giant salamanders (Dicamptodon tenebrosus) and coastal cutthroat trout (Oncorhynchus clarki clarki) are the top predators in many perennial headwater streams. Dicamptodon and cutthroat have size-structured populations with roughly corresponding size classes, and interactions between these species appear consistent with intraguild predation. My research objective was to determine the mechanisms contributing to the coexistence of Dicamptodon larvae with cutthroat trout in headwater streams, and the effects of this coexistence on factors related to Dicamptodon fitness. First, I tested for two general types of antipredator defenses of young-of-year Dicamptodon larvae against trout. Larvae were palatable to trout during initial and repeated offerings, which suggests that they may survive few encounters with trout. However, larvae increased refuge use in response to non-visual, chemical cues from trout, which likely reduces the probability of encounters with trout and contributes to their coexistence. Second, I measured the effects of cutthroat trout on Dicamptodon fitness parameters in a field experiment. Dicamptodon survival, growth, and behavior (activity level) did not differ between trout-present and trout-absent pools, although these results were compromised by unexplained gains or losses of larvae from most pools. Antipredator behaviors may promote coexistence of Dicamptodon and cutthroat trout, and may contribute to a complex series of behavioral and trophic interactions affecting lower trophic levels within headwater stream communities. Title: Coexistence of top predators in headwater streams : pathways of intraguild predation between Pacific Giant salamander larvae and cutthroat trout Author: Rundio, David E. The coexistence of multiple predators may have important consequences for the structure and function of communities. Interactions between predators may strongly affect their combined direct and indirect effects on prey populations and lower trophic levels. Predators often have size-structured populations, which may result in intraguild predation characterized by complex trophic and behavioral interactions. Coexistence of multiple predators may strongly depend on antipredator defenses of small size classes that reduce their vulnerability to predation. In Pacific Northwest forested ecosystems, Pacific giant salamanders (Dicamptodon tenebrosus) and coastal cutthroat trout (Oncorhynchus clarki clarki) are the top predators in many perennial headwater streams. Dicamptodon and cutthroat have size-structured populations with roughly corresponding size classes, and interactions between these species appear consistent with intraguild predation. My research objective was to determine the mechanisms contributing to the coexistence of Dicamptodon larvae with cutthroat trout in headwater streams, and the effects of this coexistence on factors related to Dicamptodon fitness. First, I tested for two general types of antipredator defenses of young-of-year Dicamptodon larvae against trout. Larvae were palatable to trout during initial and repeated offerings, which suggests that they may survive few encounters with trout. However, larvae increased refuge use in response to non-visual, chemical cues from trout, which likely reduces the probability of encounters with trout and contributes to their coexistence. Second, I measured the effects of cutthroat trout on Dicamptodon fitness parameters in a field experiment. Dicamptodon survival, growth, and behavior (activity level) did not differ between trout-present and trout-absent pools, although these results were compromised by unexplained gains or losses of larvae from most pools. Antipredator behaviors may promote coexistence of Dicamptodon and cutthroat trout, and may contribute to a complex series of behavioral and trophic interactions affecting lower trophic levels within headwater stream communities. Close

• 14. [Article] An evaluation in rainbow trout of biliary excretion of sulfobromophthalein and effects of biliary excretion on the toxicity of rotenone

  Biliary excretion has been of considerable interest in mammals but has not been extensively studied in fish. To understand the significance of biliary excretion in rainbow trout (Salmo gairdneri), two ...

  Citation × Citation Citation Abstract Copy Title: An evaluation in rainbow trout of biliary excretion of sulfobromophthalein and effects of biliary excretion on the toxicity of rotenone Author: Schmidt, Dana C. Biliary excretion has been of considerable interest in mammals but has not been extensively studied in fish. To understand the significance of biliary excretion in rainbow trout (Salmo gairdneri), two studies were conducted. The objective of the initial study was to evaluate the ability of rainbow trout to excrete a foreign compound typically excreted by the vertebrate liver. This problem was approached by evaluating biliary excretion and metabolism of sulfobromophthalein (BSP) in trout and comparing the results with literature values for mammals. Results indicated this dye is metabolized and excreted similarily in trout, dogfish (Squalus acanthias) and mammals. Large differences between trout and other species in transport maxima (Tm) of BSP based on body weights, were explained when the Tm values were based on liver blood clearance of BSP, a physiological rate reflecting blood flow. The objective of the second study was to determine if biliary excretion affects the toxicity of a foreign compound toxic to trout. This problem was approached by evaluating the effect of bile and cystic duct ligation on the mean lethal dose (LD 50) of rotenone to trout. To determine if biliary excretion affected the selective toxicity of this compound to trout, the effect of bile duct ligation on the rotenone LD 50 to rats was estimated and the results were compared with those obtained from the trout. The toxicant was administered intraperitoneally and intravenously in trout and intraperitoneally in rats. No increase in toxicity of rotenone occurred upon surgical impairment of bile flow in either the trout or the rats, Similarities in the toxicity of rotenone to trout and rats were observed when the toxicant was administered intraperitoneally, The data suggest the selective toxicity of rotenone to fish may be primarily caused by different routes of entry. The results of these experiments indicate the excretory functions of the liver of fish and mammals are similar. Title: An evaluation in rainbow trout of biliary excretion of sulfobromophthalein and effects of biliary excretion on the toxicity of rotenone Author: Schmidt, Dana C. Biliary excretion has been of considerable interest in mammals but has not been extensively studied in fish. To understand the significance of biliary excretion in rainbow trout (Salmo gairdneri), two studies were conducted. The objective of the initial study was to evaluate the ability of rainbow trout to excrete a foreign compound typically excreted by the vertebrate liver. This problem was approached by evaluating biliary excretion and metabolism of sulfobromophthalein (BSP) in trout and comparing the results with literature values for mammals. Results indicated this dye is metabolized and excreted similarily in trout, dogfish (Squalus acanthias) and mammals. Large differences between trout and other species in transport maxima (Tm) of BSP based on body weights, were explained when the Tm values were based on liver blood clearance of BSP, a physiological rate reflecting blood flow. The objective of the second study was to determine if biliary excretion affects the toxicity of a foreign compound toxic to trout. This problem was approached by evaluating the effect of bile and cystic duct ligation on the mean lethal dose (LD 50) of rotenone to trout. To determine if biliary excretion affected the selective toxicity of this compound to trout, the effect of bile duct ligation on the rotenone LD 50 to rats was estimated and the results were compared with those obtained from the trout. The toxicant was administered intraperitoneally and intravenously in trout and intraperitoneally in rats. No increase in toxicity of rotenone occurred upon surgical impairment of bile flow in either the trout or the rats, Similarities in the toxicity of rotenone to trout and rats were observed when the toxicant was administered intraperitoneally, The data suggest the selective toxicity of rotenone to fish may be primarily caused by different routes of entry. The results of these experiments indicate the excretory functions of the liver of fish and mammals are similar. Close

• 15. [Article] Food relations and production of cutthroat trout, Salmo clarki clarki Richardson, in an experimental stream

  Production, food consumption and food habits by groups of small, mixed and large sizes of cutthroat trout were studied in enriched and unenriched sections of the Berry Creek Experimental Stream, Oregon ...

  Citation × Citation Citation Abstract Copy Title: Food relations and production of cutthroat trout, Salmo clarki clarki Richardson, in an experimental stream Author: McIntyre, John D. Production, food consumption and food habits by groups of small, mixed and large sizes of cutthroat trout were studied in enriched and unenriched sections of the Berry Creek Experimental Stream, Oregon State University. Continuous introduction of sucrose and urea to portions of the stream resulted in heavy growth of Sphaerotilus natans which supported large biomasses of benthic insects. Production was estimated from monthly changes of biomass. Measurements of growth rates of experimental fish and the relationship between rates of growth and rates of food consumption of fish held in aquaria made estimates of food consumption by the stream fish possible. Analyses were made of the stomach contents of trout removed monthly from the experimental sections. The seasonal contribution to trout food consumption by the important food groups was estimated. Measurements of benthic biomass showed that insects especially midge larvae, benefited greatly from the Sphaerotilus in the enriched sections but organic drift did not increase markedly as a result of enrichment. In both enriched and unenriched sections trout production and food consumption values were highest for small trout, intermediate for mixed sizes and lowest for large trout. Production and food consumption by all size groups of trout increased greatly as a result of enrichment. Title: Food relations and production of cutthroat trout, Salmo clarki clarki Richardson, in an experimental stream Author: McIntyre, John D. Production, food consumption and food habits by groups of small, mixed and large sizes of cutthroat trout were studied in enriched and unenriched sections of the Berry Creek Experimental Stream, Oregon State University. Continuous introduction of sucrose and urea to portions of the stream resulted in heavy growth of Sphaerotilus natans which supported large biomasses of benthic insects. Production was estimated from monthly changes of biomass. Measurements of growth rates of experimental fish and the relationship between rates of growth and rates of food consumption of fish held in aquaria made estimates of food consumption by the stream fish possible. Analyses were made of the stomach contents of trout removed monthly from the experimental sections. The seasonal contribution to trout food consumption by the important food groups was estimated. Measurements of benthic biomass showed that insects especially midge larvae, benefited greatly from the Sphaerotilus in the enriched sections but organic drift did not increase markedly as a result of enrichment. In both enriched and unenriched sections trout production and food consumption values were highest for small trout, intermediate for mixed sizes and lowest for large trout. Production and food consumption by all size groups of trout increased greatly as a result of enrichment. Close

• 16. [Article] Landscape-scale evaluation of genetic structure among barrier-isolated populations of coastal cutthroat trout, Oncorhynchus clarki clarki

  Citation × Citation Citation Abstract Copy Title: Landscape-scale evaluation of genetic structure among barrier-isolated populations of coastal cutthroat trout, Oncorhynchus clarki clarki Author: Guy, Troy J. Title: Landscape-scale evaluation of genetic structure among barrier-isolated populations of coastal cutthroat trout, Oncorhynchus clarki clarki Author: Guy, Troy J. Close

• 17. [Article] Geographic variation in genetic and meristic characters of coastal cutthroat trout (Oncorhynchus clarki clarki)

  Citation × Citation Citation Abstract Copy Title: Geographic variation in genetic and meristic characters of coastal cutthroat trout (Oncorhynchus clarki clarki) Author: Williams, Thomas Herbert Title: Geographic variation in genetic and meristic characters of coastal cutthroat trout (Oncorhynchus clarki clarki) Author: Williams, Thomas Herbert Close

• 18. [Article] Bioenergetic evaluation of diel vertical migration by bull trout

  I evaluated hypotheses related to growth as a driver of depth use and diel vertical migration by bull trout (Salvelinus confluentus) in a thermally stratified reservoir. I applied a bioenergetic model ...

  Citation × Citation Citation Abstract Copy Title: Bioenergetic evaluation of diel vertical migration by bull trout Author: Eckmann, Madeleine I evaluated hypotheses related to growth as a driver of depth use and diel vertical migration by bull trout (Salvelinus confluentus) in a thermally stratified reservoir. I applied a bioenergetic model to evaluate growth of bull trout in relation to potential patterns of diel depth use by bull trout in Ross Lake, Washington. Modeled patterns of growth were derived from observed vertical distributions of temperature and prey availability. I also observed bull trout depth (and corresponding temperature) use patterns to determine if observed behaviors corresponded with those predicted to maximize growth. Results of this work suggest that bull trout migrations beyond 25 m deep in Ross Lake cannot be explained exclusively by growth and survival alone, two common explanations for diel vertical migration. These deeper excursions may be explained by a third driver that has not been previously emphasized: the importance of colder water for gametogenesis. Further evaluation of this hypothesis as a means of explaining diel vertical migration for bull trout and other fish species in similar environments is warranted. Title: Bioenergetic evaluation of diel vertical migration by bull trout Author: Eckmann, Madeleine I evaluated hypotheses related to growth as a driver of depth use and diel vertical migration by bull trout (Salvelinus confluentus) in a thermally stratified reservoir. I applied a bioenergetic model to evaluate growth of bull trout in relation to potential patterns of diel depth use by bull trout in Ross Lake, Washington. Modeled patterns of growth were derived from observed vertical distributions of temperature and prey availability. I also observed bull trout depth (and corresponding temperature) use patterns to determine if observed behaviors corresponded with those predicted to maximize growth. Results of this work suggest that bull trout migrations beyond 25 m deep in Ross Lake cannot be explained exclusively by growth and survival alone, two common explanations for diel vertical migration. These deeper excursions may be explained by a third driver that has not been previously emphasized: the importance of colder water for gametogenesis. Further evaluation of this hypothesis as a means of explaining diel vertical migration for bull trout and other fish species in similar environments is warranted. Close

• 19. [Article] The influence of natural mortality and other life history factors on the yield to the angler of planted cutthroat trout in Munsel Lake, Oregon

  Citation × Citation Citation Abstract Copy Title: The influence of natural mortality and other life history factors on the yield to the angler of planted cutthroat trout in Munsel Lake, Oregon Author: Hansen, David Title: The influence of natural mortality and other life history factors on the yield to the angler of planted cutthroat trout in Munsel Lake, Oregon Author: Hansen, David Close

• 20. [Article] Life history of rainbow trout and considerations for introducing steelhead into southern Chile

  Citation × Citation Citation Abstract Copy Title: Life history of rainbow trout and considerations for introducing steelhead into southern Chile Author: Poblete Arellano, Tirso S. Title: Life history of rainbow trout and considerations for introducing steelhead into southern Chile Author: Poblete Arellano, Tirso S. Close