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• 11. [Article] The use of logistic regression for developing habitat association models

  Quantitative habitat models of wildlife-habitat relationships are developed to formalize our current understanding about an ecological system. A habitat association model is one of these models that is ...

  Citation × Citation Citation Abstract Copy Title: The use of logistic regression for developing habitat association models Author: Sjamsoe'oed, Roza Quantitative habitat models of wildlife-habitat relationships are developed to formalize our current understanding about an ecological system. A habitat association model is one of these models that is useful for answering questions about how the habitat is occupied, how much growth habitat is required by the animal, or how the animal selects its food and habitat. Radio telemetry is adopted as a technique for studying home range and habitat use. The major objective of a radio telemetry study is to collect behavioral or demographic data in order to be able to estimate population parameters for home range and habitat selection. A radio telemetry study is a kind of multinomial experiment. The Logistic Regression Model is often used for estimating the relationship between animal activities and the habitat characteristics of the location used (animal preference). However, this model is not a good model for the telemetry data. Under this model, the slope parameter estimate becomes lower and farther from the true value as the Average Habitat Quality (AHQ) increases, with Diversity fixed. The Multinomial Model is better suited to telemetry data. Using the Logistic Regression Model, a habitat association study can be conducted in conjunction with adaptive cluster sampling. In terms of the variance of the regression parameter estimate, adaptive cluster sampling is better than simple random sampling. Adaptive sampling plans are also satisfied for habitat association analysis with imperfect detectability. Title: The use of logistic regression for developing habitat association models Author: Sjamsoe'oed, Roza Quantitative habitat models of wildlife-habitat relationships are developed to formalize our current understanding about an ecological system. A habitat association model is one of these models that is useful for answering questions about how the habitat is occupied, how much growth habitat is required by the animal, or how the animal selects its food and habitat. Radio telemetry is adopted as a technique for studying home range and habitat use. The major objective of a radio telemetry study is to collect behavioral or demographic data in order to be able to estimate population parameters for home range and habitat selection. A radio telemetry study is a kind of multinomial experiment. The Logistic Regression Model is often used for estimating the relationship between animal activities and the habitat characteristics of the location used (animal preference). However, this model is not a good model for the telemetry data. Under this model, the slope parameter estimate becomes lower and farther from the true value as the Average Habitat Quality (AHQ) increases, with Diversity fixed. The Multinomial Model is better suited to telemetry data. Using the Logistic Regression Model, a habitat association study can be conducted in conjunction with adaptive cluster sampling. In terms of the variance of the regression parameter estimate, adaptive cluster sampling is better than simple random sampling. Adaptive sampling plans are also satisfied for habitat association analysis with imperfect detectability. Close

• 12. [Article] The Nehalem Estuary

  Citation × Citation Citation Abstract Copy Title: The Nehalem Estuary Title: The Nehalem Estuary Close

• 13. [Article] Abundance and habitat associations of Washington ground squirrels in north-central Oregon

  Much of the Columbia River Basin has been cultivated for agriculture, which has reduced and fragmented the native shrub-steppe habitats. As a result, the range of the Washington ground squirrel (Spermophilus ...

  Citation × Citation Citation Abstract Copy Title: Abundance and habitat associations of Washington ground squirrels in north-central Oregon Author: Greene, Eric Much of the Columbia River Basin has been cultivated for agriculture, which has reduced and fragmented the native shrub-steppe habitats. As a result, the range of the Washington ground squirrel (Spermophilus washingtoni) has been significantly reduced, prompting the states of Washington and Oregon to review their status. Consequently, I investigated abundance and habitat selection of Washington ground squirrels on the Boardman Bombing Range, Morrow County, Oregon during February through July of 1996 - 1997. Transect surveys were used to determine relative abundance among seven habitats, and live-trapping was used to compare density of squirrels in habitats in which they were present. Habitat associations were determined by comparing vegetative and soil characteristics at occupied sites and unoccupied sites. I made comparisons at two levels of resolution: a macro-habitat and a micro-habitat comparison at the colony level. Micro-habitat analysis used matched-pair logistic regression to compare habitat characteristics of colonies to a paired site where squirrels were not present. I located 44 colonies to investigate the habitat associations of this species. Transect surveys indicated highest densities in sagebrush, followed by grassland habitat. No squirrels were detected in bitterbrush or low-shrub habitats during the transect surveys. Results from capture-recapture methods also suggested higher densities in sagebrush habitat. Recruitment was highest in sagebrush followed by bunchgrass and low-shrub habitats. Mean weight for adult and juvenile squirrels were highest in bunchgrass habitat, followed by sagebrush and low-shrub. Mean maximum distance moved was greater for males than females (P = 0.0006) for adults and juveniles alike, while sex-ratios favored females in both age classes. Habitat associations at the macro-habitat level revealed selection for sites with a higher silt content (Warden soils) of the soil (P = 0.0006) and higher vegetative cover (P = 0.032). Micro-habitat associations indicated a selection for sites with a lower clay content of the soil (P = 0.004). The continued existence of Washington ground squirrels depends upon maintenance of the remaining suitable habitat, particularly large contiguous tracts. Moderate grazing does not appear to be incompatible with squirrels, though grazing intensity should be investigated in further studies. Title: Abundance and habitat associations of Washington ground squirrels in north-central Oregon Author: Greene, Eric Much of the Columbia River Basin has been cultivated for agriculture, which has reduced and fragmented the native shrub-steppe habitats. As a result, the range of the Washington ground squirrel (Spermophilus washingtoni) has been significantly reduced, prompting the states of Washington and Oregon to review their status. Consequently, I investigated abundance and habitat selection of Washington ground squirrels on the Boardman Bombing Range, Morrow County, Oregon during February through July of 1996 - 1997. Transect surveys were used to determine relative abundance among seven habitats, and live-trapping was used to compare density of squirrels in habitats in which they were present. Habitat associations were determined by comparing vegetative and soil characteristics at occupied sites and unoccupied sites. I made comparisons at two levels of resolution: a macro-habitat and a micro-habitat comparison at the colony level. Micro-habitat analysis used matched-pair logistic regression to compare habitat characteristics of colonies to a paired site where squirrels were not present. I located 44 colonies to investigate the habitat associations of this species. Transect surveys indicated highest densities in sagebrush, followed by grassland habitat. No squirrels were detected in bitterbrush or low-shrub habitats during the transect surveys. Results from capture-recapture methods also suggested higher densities in sagebrush habitat. Recruitment was highest in sagebrush followed by bunchgrass and low-shrub habitats. Mean weight for adult and juvenile squirrels were highest in bunchgrass habitat, followed by sagebrush and low-shrub. Mean maximum distance moved was greater for males than females (P = 0.0006) for adults and juveniles alike, while sex-ratios favored females in both age classes. Habitat associations at the macro-habitat level revealed selection for sites with a higher silt content (Warden soils) of the soil (P = 0.0006) and higher vegetative cover (P = 0.032). Micro-habitat associations indicated a selection for sites with a lower clay content of the soil (P = 0.004). The continued existence of Washington ground squirrels depends upon maintenance of the remaining suitable habitat, particularly large contiguous tracts. Moderate grazing does not appear to be incompatible with squirrels, though grazing intensity should be investigated in further studies. Close

• 14. [Article] Juvenile Rockfish (Sebastes spp.) Community Composition and Habitat use of Yaquina Bay, Oregon

  Estuaries, which provide viable habitat for a plethora of fish and invertebrate species, are being increasingly impacted by anthropogenic and natural forces. Estuaries are important nursery habitat for ...

  Citation × Citation Citation Abstract Copy Title: Juvenile Rockfish (Sebastes spp.) Community Composition and Habitat use of Yaquina Bay, Oregon Author: Lindsley, Amy J. Estuaries, which provide viable habitat for a plethora of fish and invertebrate species, are being increasingly impacted by anthropogenic and natural forces. Estuaries are important nursery habitat for young-of-the-year (YOY) Pacific rockfish (Sebastes spp.). Yaquina Bay, a marine-dominated estuary on the central Oregon Coast, served as a study site for the estuarine use of juvenile rockfishes, and large numbers of juvenile rockfish have been captured in this bay. Nursery habitats must provide rearing habitat, adequate food resources and refuge. A vital but lacking connection in our understanding of estuaries as nursery habitat is how rockfishes use the different microhabitats within an estuarine ecosystem. As habitats structure biotic communities, determining the ecological requirements for juvenile rockfish habitats that minimize mortality, maximize growth and increase population numbers will assist managers and biologists in managing and protecting critical high-quality nursery areas. This study provides insight into Oregon rockfish life history, evaluating the spatial and temporal use of estuarine nursery habitat by juvenile rockfishes. The primary objectives were to (1) determine which species of rockfish utilize Yaquina Bay, (2) determine seasonal variations in abundance, and (3) assess the utilization of natural (eelgrass beds, Zostera marina) versus anthropogenic (piers) estuarine habitat. I conducted a mark-recapture study of juvenile rockfishes to begin to elucidate how these species may be using different habitats in the bay. This study provides evidence for the presence of previously undocumented rockfish species, the overwinter persistence of juvenile rockfish in the estuary, some degree of site fidelity, and apparent minimal movement of juvenile rockfish in the Yaquina Bay estuary during the period of this study, as well as a shift in rockfish community dominance from S. melanops to S. maliger and S. caurinus. The survival and recapture of juveniles in both natural (Z. marina) and anthropogenic (piers) habitat demonstrates rockfishes’ successful use of multiple Yaquina Bay habitat types as nursery grounds year-round. There is seasonal variability in rockfish use of the anthropogenic and natural habitat, with the anthropogenic habitats having an overall higher capture rate and a higher occurrence of larger rockfish. All eight species S. melanops, S. maliger, S. caurinus, S. paucispinis, S. flavidus, S. nebulosus, S. pinniger and S. auriculatus are present in the natural, Z. marina habitat. Sebastes pinniger and S. auriculatus are absent from anthropogenic, pier habitat. The implications of determining habitat parameters, community interactions, seasonal changes of the fish community, and ecosystem mechanisms may be invaluable to support further recreational and commercial fishing and help sustain or increase adult populations. My findings present a significant contribution towards the proper management and conservation of essential habitat for rockfish, a group of species with high commercial value and substantial recreational harvest. Title: Juvenile Rockfish (Sebastes spp.) Community Composition and Habitat use of Yaquina Bay, Oregon Author: Lindsley, Amy J. Estuaries, which provide viable habitat for a plethora of fish and invertebrate species, are being increasingly impacted by anthropogenic and natural forces. Estuaries are important nursery habitat for young-of-the-year (YOY) Pacific rockfish (Sebastes spp.). Yaquina Bay, a marine-dominated estuary on the central Oregon Coast, served as a study site for the estuarine use of juvenile rockfishes, and large numbers of juvenile rockfish have been captured in this bay. Nursery habitats must provide rearing habitat, adequate food resources and refuge. A vital but lacking connection in our understanding of estuaries as nursery habitat is how rockfishes use the different microhabitats within an estuarine ecosystem. As habitats structure biotic communities, determining the ecological requirements for juvenile rockfish habitats that minimize mortality, maximize growth and increase population numbers will assist managers and biologists in managing and protecting critical high-quality nursery areas. This study provides insight into Oregon rockfish life history, evaluating the spatial and temporal use of estuarine nursery habitat by juvenile rockfishes. The primary objectives were to (1) determine which species of rockfish utilize Yaquina Bay, (2) determine seasonal variations in abundance, and (3) assess the utilization of natural (eelgrass beds, Zostera marina) versus anthropogenic (piers) estuarine habitat. I conducted a mark-recapture study of juvenile rockfishes to begin to elucidate how these species may be using different habitats in the bay. This study provides evidence for the presence of previously undocumented rockfish species, the overwinter persistence of juvenile rockfish in the estuary, some degree of site fidelity, and apparent minimal movement of juvenile rockfish in the Yaquina Bay estuary during the period of this study, as well as a shift in rockfish community dominance from S. melanops to S. maliger and S. caurinus. The survival and recapture of juveniles in both natural (Z. marina) and anthropogenic (piers) habitat demonstrates rockfishes’ successful use of multiple Yaquina Bay habitat types as nursery grounds year-round. There is seasonal variability in rockfish use of the anthropogenic and natural habitat, with the anthropogenic habitats having an overall higher capture rate and a higher occurrence of larger rockfish. All eight species S. melanops, S. maliger, S. caurinus, S. paucispinis, S. flavidus, S. nebulosus, S. pinniger and S. auriculatus are present in the natural, Z. marina habitat. Sebastes pinniger and S. auriculatus are absent from anthropogenic, pier habitat. The implications of determining habitat parameters, community interactions, seasonal changes of the fish community, and ecosystem mechanisms may be invaluable to support further recreational and commercial fishing and help sustain or increase adult populations. My findings present a significant contribution towards the proper management and conservation of essential habitat for rockfish, a group of species with high commercial value and substantial recreational harvest. Close

• 15. [Article] The evolution of mapping habitat for northern spotted owls (Strix occidentalis caurina): A comparison of photo-interpreted, Landsat-based, and lidar-based habitat maps

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Elsevier ...

  Citation × Citation Citation Abstract Copy Title: The evolution of mapping habitat for northern spotted owls (Strix occidentalis caurina): A comparison of photo-interpreted, Landsat-based, and lidar-based habitat maps Author: Ackers, Steven H., Dugger, Katie M., Davis, Raymond J., Olsen, Keith A. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/remote-sensing-of-environment. Title: The evolution of mapping habitat for northern spotted owls (Strix occidentalis caurina): A comparison of photo-interpreted, Landsat-based, and lidar-based habitat maps Author: Ackers, Steven H., Dugger, Katie M., Davis, Raymond J., Olsen, Keith A. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/remote-sensing-of-environment. Close

• 16. [Article] Individual Habitat Quotas for Fisheries

  Research Paper

  Citation × Citation Citation Abstract Copy Title: Individual Habitat Quotas for Fisheries Author: Holland, Daniel S., Schnier, Kurt E. Research Paper Title: Individual Habitat Quotas for Fisheries Author: Holland, Daniel S., Schnier, Kurt E. Research Paper Close

• 17. [Article] An economic analysis of alternative water allocations and habitat investments for anadromous fish production, John Day Basin, Oregon

  This thesis focuses on the economic efficiency of alternative habitat, streamfiow, and land use allocations within a major drainage of the Pacific Northwest. Specifically, productivity of present habitat and ...

  Citation × Citation Citation Abstract Copy Title: An economic analysis of alternative water allocations and habitat investments for anadromous fish production, John Day Basin, Oregon Author: Cerda, Arcadio Alberto This thesis focuses on the economic efficiency of alternative habitat, streamfiow, and land use allocations within a major drainage of the Pacific Northwest. Specifically, productivity of present habitat and streamfiow conditions is evaluated with respect to anadromous fish species (chinook salmon and steelhead trout) in the John Day River Basin, a high-desert system in the Pacific Northwest. Alternative water allocations and fish habitat enhancements to improve anadromous fish productivity are also examined. This biophysical information is combined with economics concepts to evaluate comparative benefits and economic efficiency of selected technically feasible habitat/streamflow alternatives. The John Day River Basin is used as a case study because it provides one of the most significant runs of wild summer steelhead trout and spring chinook salmon in the Columbia River Basin. Specific categories of alternative enhancements included water transfers to instream flow, habitat vegetation improvements, and habitat structural measures. The benefits of changes in fish numbers are valued through the travel cost method. Costs of habitat investments are derived from a synthesis of cost data for similar investments for the region. For most lower-reach stream sections, benefits of habitat investments/streamflow alternatives do not equal costs. However, changes in water allocations and habitat do appear economically efficient to some upper reaches. The main results suggest that economic efficiency varies greatly within the system, indicating the need for site-specific proposals for streamfiow or habitat alterations within this or similar high desert streams. In addition to providing preliminary estimates of the economic efficency of streamfiow and habitat investments, this thesis serves as a methodological template for future integrated bioeconomic evaluations of water and fishery management issues. Title: An economic analysis of alternative water allocations and habitat investments for anadromous fish production, John Day Basin, Oregon Author: Cerda, Arcadio Alberto This thesis focuses on the economic efficiency of alternative habitat, streamfiow, and land use allocations within a major drainage of the Pacific Northwest. Specifically, productivity of present habitat and streamfiow conditions is evaluated with respect to anadromous fish species (chinook salmon and steelhead trout) in the John Day River Basin, a high-desert system in the Pacific Northwest. Alternative water allocations and fish habitat enhancements to improve anadromous fish productivity are also examined. This biophysical information is combined with economics concepts to evaluate comparative benefits and economic efficiency of selected technically feasible habitat/streamflow alternatives. The John Day River Basin is used as a case study because it provides one of the most significant runs of wild summer steelhead trout and spring chinook salmon in the Columbia River Basin. Specific categories of alternative enhancements included water transfers to instream flow, habitat vegetation improvements, and habitat structural measures. The benefits of changes in fish numbers are valued through the travel cost method. Costs of habitat investments are derived from a synthesis of cost data for similar investments for the region. For most lower-reach stream sections, benefits of habitat investments/streamflow alternatives do not equal costs. However, changes in water allocations and habitat do appear economically efficient to some upper reaches. The main results suggest that economic efficiency varies greatly within the system, indicating the need for site-specific proposals for streamfiow or habitat alterations within this or similar high desert streams. In addition to providing preliminary estimates of the economic efficency of streamfiow and habitat investments, this thesis serves as a methodological template for future integrated bioeconomic evaluations of water and fishery management issues. Close

• 18. [Article] Identification and mapping of habitat types in the vicinity of Mount Tolman in eastern Washington

  Studies were conducted in the vicinity of Mount Tolman on the Colville Indian Reservation in eastern Washington in order to identify vegetation habitat types of the area. After field studies were completed, ...

  Citation × Citation Citation Abstract Copy Title: Identification and mapping of habitat types in the vicinity of Mount Tolman in eastern Washington Author: Wilson, Mary Loverna Studies were conducted in the vicinity of Mount Tolman on the Colville Indian Reservation in eastern Washington in order to identify vegetation habitat types of the area. After field studies were completed, Daubenmire's keys to habitat types of eastern Washington (1968, 1970) were used to determine habitat types of the area. On the basis of sampling results, eleven habitat types were identified and described. This information was used in conjunction with aerial photointerpretation to prepare a vegetation map. Daubenmire's baseline studies, from which the habitat type keys were developed, were conducted in pristine climax stands. The Mount Tolman study area vegetation has been subjected to human disturbance for many years. Agriculture, grazing, logging, mining, and urbanization have all had an impact on the natural vegetation of the area. It was of interest to see at what levels of disturbance it would still be possible to determine habitat types from remnant native vegetation. Steppe habitat types identified were Agropyron spicatum/Festuca idahoensis and Purshia tridentata/Agropyron spicatum. Very little vegetation representative of these habitat types remained in the study area because of conversion of most open land to either agricultural crops or pasture. Most steppe portions of the study area had been heavily grazed and supported disclimax vegetation dominated by Bromus tectorum and other weedy species. Four Pinus ponderosa habitat types were identified. They were Pinus ponderosa/Agropyron spicatum, Pinus ponderosa/Festuca idahoensis, Pinus ponderosa/Purshia tridentata, and Pinus ponderosa/Symphoricarpos albus. Together they composed 43 percent of the study area. Three other forest habitats, Pseudotsuga menziesii/Symphoricarpos albus, Pseudotsuga menziesii/Physocarpus malvaceus, and Abies grandis/Pachistima myrsinites, occupied 30 percent of the study area. Two riparian habitat types occurred consistently in the creek drainages. One of these was Crataegus douglasii/ Symphoricarpus albus, both the Crataegus phase, and Populus tremuloides phase; the other was Alnus incana/Lysichitum americanum. Using Daubenmire's keys, coupled with information about seral communities and successional patterns, proved to be effective in determining habitat types in all but the most disturbed sites. Title: Identification and mapping of habitat types in the vicinity of Mount Tolman in eastern Washington Author: Wilson, Mary Loverna Studies were conducted in the vicinity of Mount Tolman on the Colville Indian Reservation in eastern Washington in order to identify vegetation habitat types of the area. After field studies were completed, Daubenmire's keys to habitat types of eastern Washington (1968, 1970) were used to determine habitat types of the area. On the basis of sampling results, eleven habitat types were identified and described. This information was used in conjunction with aerial photointerpretation to prepare a vegetation map. Daubenmire's baseline studies, from which the habitat type keys were developed, were conducted in pristine climax stands. The Mount Tolman study area vegetation has been subjected to human disturbance for many years. Agriculture, grazing, logging, mining, and urbanization have all had an impact on the natural vegetation of the area. It was of interest to see at what levels of disturbance it would still be possible to determine habitat types from remnant native vegetation. Steppe habitat types identified were Agropyron spicatum/Festuca idahoensis and Purshia tridentata/Agropyron spicatum. Very little vegetation representative of these habitat types remained in the study area because of conversion of most open land to either agricultural crops or pasture. Most steppe portions of the study area had been heavily grazed and supported disclimax vegetation dominated by Bromus tectorum and other weedy species. Four Pinus ponderosa habitat types were identified. They were Pinus ponderosa/Agropyron spicatum, Pinus ponderosa/Festuca idahoensis, Pinus ponderosa/Purshia tridentata, and Pinus ponderosa/Symphoricarpos albus. Together they composed 43 percent of the study area. Three other forest habitats, Pseudotsuga menziesii/Symphoricarpos albus, Pseudotsuga menziesii/Physocarpus malvaceus, and Abies grandis/Pachistima myrsinites, occupied 30 percent of the study area. Two riparian habitat types occurred consistently in the creek drainages. One of these was Crataegus douglasii/ Symphoricarpus albus, both the Crataegus phase, and Populus tremuloides phase; the other was Alnus incana/Lysichitum americanum. Using Daubenmire's keys, coupled with information about seral communities and successional patterns, proved to be effective in determining habitat types in all but the most disturbed sites. Close

• 19. [Article] A Bioeconomic Model of Fishery-Habitat Impacts

  Abstract only.

  Citation × Citation Citation Abstract Copy Title: A Bioeconomic Model of Fishery-Habitat Impacts Author: Kahui, Viktoria, Armstrong, Claire Abstract only. Title: A Bioeconomic Model of Fishery-Habitat Impacts Author: Kahui, Viktoria, Armstrong, Claire Abstract only. Close

• 20. [Article] Ecology of aquatic habitats associated with stream margins

  The morphology and ecological importance of habitats associated with the margin of third-order stream channels in the Oregon Cascades were studied in streams in three different riparian types: 450-year-old ...

  Citation × Citation Citation Abstract Copy Title: Ecology of aquatic habitats associated with stream margins Author: Moore, Kelly M. S. The morphology and ecological importance of habitats associated with the margin of third-order stream channels in the Oregon Cascades were studied in streams in three different riparian types: 450-year-old conifers, 40-year-old alder, and an open, herbaceous-dominated clearcut. Margins, backwaters, and side channels in streams create important habitat for fry of cutthroat trout (Salmo clarki clarki) and support benthic invertebrate assemblages of high denSity and distinctive composition. These lateral habitats are characterized by slow, shallow water, heterogeneous size distribution of substrates, abundant detritus, and by hydraulic and morphologic persistence. In the study reaches, area of lateral habitat was maximum in early summer, averaging 15 percent of total stream area. The amount of lateral habitat decreased with either lower or higher flows. During a 1-yr period lateral habitats in the coniferous site changed the least. The volume and hydraulic characteristics of individual lateral habitats were functions of the morphology of the structures that formed the habitat and the orientation and location of the habitat relative to the central axis of the strea Large woody debris and large boulders created lateral habitats that were larger, had longer hydrologic residence times, and were more persistent when streamflow changed than lateral habitats formed by small boulders and cobble. Stream margins and backwaters were major sites of detritus storage. Average detritus standing crop in backwaters and stream margins was 5 to 15 times greater than standing crops in riffles or pools in the same stream. Detritus at the coniferous reach had higher organic matter content and a greater percentage of lignin than detritus at the deciduous reach. Detritus at the open reach was much lower in organic matter content, but the ratio of cellulose to lignin was greater than in the forested reaches. The activity of microbial assemblages associated with fine detritus was generally highest at the open reach. Average standing crop of chlorophyll a was highest at the open site. The abundance and quality of nutritional resources in lateral habitats were reflected in the associated invertebrate communities. High densities of chironomids, early instar Ephemeroptera and Plecoptera, oligochaetes, and micro-crustacea were found in stream margins and backwaters at each site. Mean invertebrate density in lateral habitats was similar in the coniferous (66,500 individuals/m²) and open (75,000 individuals/m²) reaches, but lower at the deciduous site (24,000 individuals/m²). Collector-gatherer, shredder, and predator functional feeding groups were well represented at each site. Differences in functional roup organization between reaches were primarily related tp increased numbers of herbivorous collector-gatherers at the open site and a greater relative abundance of shredders at the deciduous site. Cutthroat trout fry populations were directly linked to the length of stream edge and the area of lateral habitat. Fry occupy lateral habitats immediately after emergence and may not move from lateral habitats until the end of their first summer. In an experimental manipulation of nine stream reaches, increasing lateral habitat prior to fry emergence resulted in 2.5 times higher fry density than in control reaches and reducing lateral habitat virtually eliminated fry populations. Cutthroat trout in headwater streams continue to use lateral habitats throughout their life cycle as refuge for all age classes during high streamflow and by adult trout as spawning areas. Title: Ecology of aquatic habitats associated with stream margins Author: Moore, Kelly M. S. The morphology and ecological importance of habitats associated with the margin of third-order stream channels in the Oregon Cascades were studied in streams in three different riparian types: 450-year-old conifers, 40-year-old alder, and an open, herbaceous-dominated clearcut. Margins, backwaters, and side channels in streams create important habitat for fry of cutthroat trout (Salmo clarki clarki) and support benthic invertebrate assemblages of high denSity and distinctive composition. These lateral habitats are characterized by slow, shallow water, heterogeneous size distribution of substrates, abundant detritus, and by hydraulic and morphologic persistence. In the study reaches, area of lateral habitat was maximum in early summer, averaging 15 percent of total stream area. The amount of lateral habitat decreased with either lower or higher flows. During a 1-yr period lateral habitats in the coniferous site changed the least. The volume and hydraulic characteristics of individual lateral habitats were functions of the morphology of the structures that formed the habitat and the orientation and location of the habitat relative to the central axis of the strea Large woody debris and large boulders created lateral habitats that were larger, had longer hydrologic residence times, and were more persistent when streamflow changed than lateral habitats formed by small boulders and cobble. Stream margins and backwaters were major sites of detritus storage. Average detritus standing crop in backwaters and stream margins was 5 to 15 times greater than standing crops in riffles or pools in the same stream. Detritus at the coniferous reach had higher organic matter content and a greater percentage of lignin than detritus at the deciduous reach. Detritus at the open reach was much lower in organic matter content, but the ratio of cellulose to lignin was greater than in the forested reaches. The activity of microbial assemblages associated with fine detritus was generally highest at the open reach. Average standing crop of chlorophyll a was highest at the open site. The abundance and quality of nutritional resources in lateral habitats were reflected in the associated invertebrate communities. High densities of chironomids, early instar Ephemeroptera and Plecoptera, oligochaetes, and micro-crustacea were found in stream margins and backwaters at each site. Mean invertebrate density in lateral habitats was similar in the coniferous (66,500 individuals/m²) and open (75,000 individuals/m²) reaches, but lower at the deciduous site (24,000 individuals/m²). Collector-gatherer, shredder, and predator functional feeding groups were well represented at each site. Differences in functional roup organization between reaches were primarily related tp increased numbers of herbivorous collector-gatherers at the open site and a greater relative abundance of shredders at the deciduous site. Cutthroat trout fry populations were directly linked to the length of stream edge and the area of lateral habitat. Fry occupy lateral habitats immediately after emergence and may not move from lateral habitats until the end of their first summer. In an experimental manipulation of nine stream reaches, increasing lateral habitat prior to fry emergence resulted in 2.5 times higher fry density than in control reaches and reducing lateral habitat virtually eliminated fry populations. Cutthroat trout in headwater streams continue to use lateral habitats throughout their life cycle as refuge for all age classes during high streamflow and by adult trout as spawning areas. Close