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• 21. [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

• 22. [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

• 23. [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

• 24. [Article] 2012 Metolius Basin bull trout redd counts

  Abstract -- Bull trout are indigenous to the Metolius River basin; however, they were managed as a nuisance species due to their interactions with anadromous sportfish for several decades. In 1960, nuisance ...

  Citation × Citation Citation Abstract Copy Title: 2012 Metolius Basin bull trout redd counts Abstract -- Bull trout are indigenous to the Metolius River basin; however, they were managed as a nuisance species due to their interactions with anadromous sportfish for several decades. In 1960, nuisance management of bull trout ended and protection of bull trout began in 1983 with mandatory catch and release regulations throughout the Metolius River basin. In 1986, the Department initiated annual redd counts for bull trout throughout the basin to document the species status. Redd surveys showed low spawning numbers, and the Department responded by closing all tributaries downstream of Lake Creek to fishing in 1994. A Threatened listing of Columbia River bull trout under the Endangered Species Act in 1998 followed the fishery closure (Fies et al. 1996 and Lohr et al. ####). Bull trout redd counts continue in the basin in accordance with the goals of the Native Fish Conservation Policy. Title: 2012 Metolius Basin bull trout redd counts Abstract -- Bull trout are indigenous to the Metolius River basin; however, they were managed as a nuisance species due to their interactions with anadromous sportfish for several decades. In 1960, nuisance management of bull trout ended and protection of bull trout began in 1983 with mandatory catch and release regulations throughout the Metolius River basin. In 1986, the Department initiated annual redd counts for bull trout throughout the basin to document the species status. Redd surveys showed low spawning numbers, and the Department responded by closing all tributaries downstream of Lake Creek to fishing in 1994. A Threatened listing of Columbia River bull trout under the Endangered Species Act in 1998 followed the fishery closure (Fies et al. 1996 and Lohr et al. ####). Bull trout redd counts continue in the basin in accordance with the goals of the Native Fish Conservation Policy. Close

• 25. [Article] 2011 Metolius River subbasin bull trout redd counts

  Abstract -- Bull trout are indigenous to the Metolius River basin; however, they were managed as a nuisance species due to their interactions with anadromous sportfish for several decades. In 1960, nuisance ...

  Citation × Citation Citation Abstract Copy Title: 2011 Metolius River subbasin bull trout redd counts Abstract -- Bull trout are indigenous to the Metolius River basin; however, they were managed as a nuisance species due to their interactions with anadromous sportfish for several decades. In 1960, nuisance management of bull trout ended and protection of bull trout began in 1983 with mandatory catch and release regulations throughout the Metolius River basin. In 1986, the Department initiated annual redd counts for bull trout throughout the basin to document the species status. Redd surveys showed low spawning numbers, and the Department responded by closing all tributaries downstream of Lake Creek to fishing in 1994. A Threatened listing of Columbia River bull trout under the Endangered Species Act in 1998 followed the fishery closure (Fies et al. 1996 and Lohr et al. ####). Bull trout redd counts continue in the basin in accordance with the goals of the Native Fish Conservation Policy. Title: 2011 Metolius River subbasin bull trout redd counts Abstract -- Bull trout are indigenous to the Metolius River basin; however, they were managed as a nuisance species due to their interactions with anadromous sportfish for several decades. In 1960, nuisance management of bull trout ended and protection of bull trout began in 1983 with mandatory catch and release regulations throughout the Metolius River basin. In 1986, the Department initiated annual redd counts for bull trout throughout the basin to document the species status. Redd surveys showed low spawning numbers, and the Department responded by closing all tributaries downstream of Lake Creek to fishing in 1994. A Threatened listing of Columbia River bull trout under the Endangered Species Act in 1998 followed the fishery closure (Fies et al. 1996 and Lohr et al. ####). Bull trout redd counts continue in the basin in accordance with the goals of the Native Fish Conservation Policy. Close

• 26. [Article] 2010 Metolius Basin bull trout redds

  Abstract -- Bull trout are indigenous to the Metolius River basin; however, they were managed as a nuisance species due to their interactions with anadromous sportfish for several decades. In 1960, nuisance ...

  Citation × Citation Citation Abstract Copy Title: 2010 Metolius Basin bull trout redds Abstract -- Bull trout are indigenous to the Metolius River basin; however, they were managed as a nuisance species due to their interactions with anadromous sportfish for several decades. In 1960, nuisance management of bull trout ended and protection of bull trout began in 1983 with mandatory catch and release regulations throughout the Metolius River basin. In 1986, the Department initiated annual redd counts for bull trout throughout the basin to document the species status. Redd surveys showed low spawning numbers, and the Department responded by closing all tributaries downstream of Lake Creek to fishing in 1994. A Threatened listing of Columbia River bull trout under the Endangered Species Act in 1998 followed the fishery closure (Fies et al. 1996 and Lohr et al. ####). Bull trout redd counts continue in the basin in accordance with the goals of the Native Fish Conservation Policy. Title: 2010 Metolius Basin bull trout redds Abstract -- Bull trout are indigenous to the Metolius River basin; however, they were managed as a nuisance species due to their interactions with anadromous sportfish for several decades. In 1960, nuisance management of bull trout ended and protection of bull trout began in 1983 with mandatory catch and release regulations throughout the Metolius River basin. In 1986, the Department initiated annual redd counts for bull trout throughout the basin to document the species status. Redd surveys showed low spawning numbers, and the Department responded by closing all tributaries downstream of Lake Creek to fishing in 1994. A Threatened listing of Columbia River bull trout under the Endangered Species Act in 1998 followed the fishery closure (Fies et al. 1996 and Lohr et al. ####). Bull trout redd counts continue in the basin in accordance with the goals of the Native Fish Conservation Policy. Close

• 27. [Article] Florence area stocked trout evaluation, 1993

  Abstract -- This study evaluates the hatchery rainbow trout program for seventeen dunal lakes in the Siuslaw Fish District near Florence, Oregon (Figure 1). The contribution of stocking rainbow trout in ...

  Citation × Citation Citation Abstract Copy Title: Florence area stocked trout evaluation, 1993 Abstract -- This study evaluates the hatchery rainbow trout program for seventeen dunal lakes in the Siuslaw Fish District near Florence, Oregon (Figure 1). The contribution of stocking rainbow trout in coastal lakes of Oregon has not been systematically evaluated to determine the amount of recreation provided or the catch rate of the hatchery product. Estimates of the angler catch and effort from this study will be used to meet the following three objectives: 1: Describe the current fishery at 17 mid-coast Oregon dunal lakes arid make recommendations to improve the program to increase angler satisfaction. 2: determine the utilization rate and overall contribution of hatchery trout compared to the Oregon Trout Plan statewide goal of a minimum 40¼ catch of hatchery fish. 3: Determine the hatchery trout contribution to the fisheries compared to native trout in lakes with both present. Title: Florence area stocked trout evaluation, 1993 Abstract -- This study evaluates the hatchery rainbow trout program for seventeen dunal lakes in the Siuslaw Fish District near Florence, Oregon (Figure 1). The contribution of stocking rainbow trout in coastal lakes of Oregon has not been systematically evaluated to determine the amount of recreation provided or the catch rate of the hatchery product. Estimates of the angler catch and effort from this study will be used to meet the following three objectives: 1: Describe the current fishery at 17 mid-coast Oregon dunal lakes arid make recommendations to improve the program to increase angler satisfaction. 2: determine the utilization rate and overall contribution of hatchery trout compared to the Oregon Trout Plan statewide goal of a minimum 40¼ catch of hatchery fish. 3: Determine the hatchery trout contribution to the fisheries compared to native trout in lakes with both present. Close

• 28. [Article] Timing and Location of Spawning by Bull Trout and Kokanee in the Odell Lake Watershed and Heising Spring of the Metolius River Watershed, 2003-04.

  Abstract -- Although the present size of the bull trout population within the Odell Lake Recovery Unit is unknown, it appears to be quite small. Spawning by bull trout of the Odell Lake Recovery Unit occurs ...

  Citation × Citation Citation Abstract Copy Title: Timing and Location of Spawning by Bull Trout and Kokanee in the Odell Lake Watershed and Heising Spring of the Metolius River Watershed, 2003-04. Abstract -- Although the present size of the bull trout population within the Odell Lake Recovery Unit is unknown, it appears to be quite small. Spawning by bull trout of the Odell Lake Recovery Unit occurs only in the lower 0.8 km of Trapper Creek, below a falls presumed to be a barrier. Numbers of redds observed in Trapper Creek from 1996 through 2002 have ranged from one to 24. In addition to genetic effects caused by small population size, primary threats to the sustainability of these bull trout include limited spawning and rearing habitat in all streams, hybridization with brook trout in upper Trapper Creek, competition from other fish species, particularly lake trout in Odell Lake, and superimposition of kokanee salmon (O. nerka) redds on bull trout redds. The latter threat may be particularly detrimental because of the large number of kokanee that spawn in lower Trapper Creek. To address concerns of bull trout redd superimposition by bull trout, we designed studies to: 1) Assess the impacts to bull trout reproduction caused by kokanee that spawn at the same location, and 2) Develop acceptable methods to separate bull trout and kokanee that spawn in Trapper Creek, Odell Lake. The first objective will address the concerns that kokanee redds superimposed on bull trout redds will reduce the number of bull trout progeny. During the spawning season, we will cap several undisturbed bull trout redds and an equal number of redds superimposed with kokanee salmon redds. Emergent fry will be captured, identified, and enumerated; statistical comparisons of fry abundance will be made between both groups of redds. To adjust for spawner fecundity, estimates of the size of females that make each redd will be obtained visually. We intend to conduct these studies at Heising Springs on the Metolius River, which helps support one of the healthiest bull trout populations in Oregon. The second objective addresses efforts to enhance the Odell Lake bull trout population. Recently, managers installed a weir to block passage of kokanee salmon to spawning areas in Trapper Creek; bull trout were captured and placed upstream. This activity led to opposition by anglers supportive of kokanee and loss of adult bull trout by an otter that invaded the trap. Our intent is to help managers design and implement methods that 1) prevent kokanee salmon from impacting bull trout redds in Trapper Creek, 2) enable bull trout to move into and out of Trapper Creek without capture and handling, and 3) enumerate bull trout spawning in Trapper Creek. Data collected in Trapper Creek should help with design and implementation of methodologies to separate the species during the spawning season. Title: Timing and Location of Spawning by Bull Trout and Kokanee in the Odell Lake Watershed and Heising Spring of the Metolius River Watershed, 2003-04. Abstract -- Although the present size of the bull trout population within the Odell Lake Recovery Unit is unknown, it appears to be quite small. Spawning by bull trout of the Odell Lake Recovery Unit occurs only in the lower 0.8 km of Trapper Creek, below a falls presumed to be a barrier. Numbers of redds observed in Trapper Creek from 1996 through 2002 have ranged from one to 24. In addition to genetic effects caused by small population size, primary threats to the sustainability of these bull trout include limited spawning and rearing habitat in all streams, hybridization with brook trout in upper Trapper Creek, competition from other fish species, particularly lake trout in Odell Lake, and superimposition of kokanee salmon (O. nerka) redds on bull trout redds. The latter threat may be particularly detrimental because of the large number of kokanee that spawn in lower Trapper Creek. To address concerns of bull trout redd superimposition by bull trout, we designed studies to: 1) Assess the impacts to bull trout reproduction caused by kokanee that spawn at the same location, and 2) Develop acceptable methods to separate bull trout and kokanee that spawn in Trapper Creek, Odell Lake. The first objective will address the concerns that kokanee redds superimposed on bull trout redds will reduce the number of bull trout progeny. During the spawning season, we will cap several undisturbed bull trout redds and an equal number of redds superimposed with kokanee salmon redds. Emergent fry will be captured, identified, and enumerated; statistical comparisons of fry abundance will be made between both groups of redds. To adjust for spawner fecundity, estimates of the size of females that make each redd will be obtained visually. We intend to conduct these studies at Heising Springs on the Metolius River, which helps support one of the healthiest bull trout populations in Oregon. The second objective addresses efforts to enhance the Odell Lake bull trout population. Recently, managers installed a weir to block passage of kokanee salmon to spawning areas in Trapper Creek; bull trout were captured and placed upstream. This activity led to opposition by anglers supportive of kokanee and loss of adult bull trout by an otter that invaded the trap. Our intent is to help managers design and implement methods that 1) prevent kokanee salmon from impacting bull trout redds in Trapper Creek, 2) enable bull trout to move into and out of Trapper Creek without capture and handling, and 3) enumerate bull trout spawning in Trapper Creek. Data collected in Trapper Creek should help with design and implementation of methodologies to separate the species during the spawning season. Close

• 29. [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

• 30. [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