Search

Search Results

• 681. [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

• 682. [Article] Demonstration of fiber optic distributed temperature sensing to differentiate cold water refuge between ground water inflows and hyporheic exchange

  Recent developments in Distributed Temperature Sensing (DTS) have allowed new insight into the surface-to-ground water interaction. The continuous temperature measurement by the DTS allows for cool water ...

  Citation × Citation Citation Abstract Copy Title: Demonstration of fiber optic distributed temperature sensing to differentiate cold water refuge between ground water inflows and hyporheic exchange Author: Collier, Michael W. Recent developments in Distributed Temperature Sensing (DTS) have allowed new insight into the surface-to-ground water interaction. The continuous temperature measurement by the DTS allows for cool water inflows to be located during warm summer months. These cool water inflows can then be differentiated between ground water and hyporheic exchange. The cool water inflows are important to many species that inhabit the rivers of the Western United States. As temperatures increase due to climate change the importance of cool water inflows will grow. This study used fiber optic cable and the DTS system to measure the temperature in 2km of the Walla Walla River, near Milton-Freewater, Oregon. The temperature data was split into nighttime and daytime averages. The correlation between these two data sets was calculated to reveal when the daytime and nighttime data followed the same cooling pattern (evidence of ground water inflow) or when the nighttime temperature increased, but the daytime temperature decreased (evidence of hyporheic exchange). Nine areas of apparent ground water inflow and nine areas of expected hyporheic exchange were identified. The average quantity of inflow at each ground water site was calculated as 0.04 m3/s. The computed average hyporheic exchange depth along the 2000 m channel was 0.32 m. The located cold water inflows were compared to salmon and trout location from a US Fish and Wildlife Survey. This comparison showed that the cool mid-day inflows (either ground water or hyporheic exchange locations) made up 1/3 of the study reach length and had approximately 60% of the cold water fish. Half of the cool water inflow sites did not have fish present during the survey which suggests that while influent cool water is a major factor for fish congregation, it is not the sole factor. Title: Demonstration of fiber optic distributed temperature sensing to differentiate cold water refuge between ground water inflows and hyporheic exchange Author: Collier, Michael W. Recent developments in Distributed Temperature Sensing (DTS) have allowed new insight into the surface-to-ground water interaction. The continuous temperature measurement by the DTS allows for cool water inflows to be located during warm summer months. These cool water inflows can then be differentiated between ground water and hyporheic exchange. The cool water inflows are important to many species that inhabit the rivers of the Western United States. As temperatures increase due to climate change the importance of cool water inflows will grow. This study used fiber optic cable and the DTS system to measure the temperature in 2km of the Walla Walla River, near Milton-Freewater, Oregon. The temperature data was split into nighttime and daytime averages. The correlation between these two data sets was calculated to reveal when the daytime and nighttime data followed the same cooling pattern (evidence of ground water inflow) or when the nighttime temperature increased, but the daytime temperature decreased (evidence of hyporheic exchange). Nine areas of apparent ground water inflow and nine areas of expected hyporheic exchange were identified. The average quantity of inflow at each ground water site was calculated as 0.04 m3/s. The computed average hyporheic exchange depth along the 2000 m channel was 0.32 m. The located cold water inflows were compared to salmon and trout location from a US Fish and Wildlife Survey. This comparison showed that the cool mid-day inflows (either ground water or hyporheic exchange locations) made up 1/3 of the study reach length and had approximately 60% of the cold water fish. Half of the cool water inflow sites did not have fish present during the survey which suggests that while influent cool water is a major factor for fish congregation, it is not the sole factor. Close

• 683. [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

• 684. [Article] Movement Patterns of Rockfishes at the Redfish Rocks Marine Reserve, Oregon

  The effects of Marine protected areas (MPAs) on adult fish populations depend on the degree of protection provided, which is partly a function of MPA size and the spatial extent of fish movements. The ...

  Citation × Citation Citation Abstract Copy Title: Movement Patterns of Rockfishes at the Redfish Rocks Marine Reserve, Oregon Author: Calvanese, Thomas P. The effects of Marine protected areas (MPAs) on adult fish populations depend on the degree of protection provided, which is partly a function of MPA size and the spatial extent of fish movements. The Redfish Rocks Marine Reserve (RRMR) and MPA, located on the south coast of Oregon near Port Orford, went into effect on January 1, 2012. The boundaries of the RRMR were informed by the experience of local fishermen, but without explicit knowledge of the movement patterns of individual fish. One of the intended effects of this reserve was to provide protection for Pacific rockfishes that had been targeted there by the live fish fishery. We conducted a 17- month acoustic telemetry study to document the movement patterns of 20 individuals (6-7 each) of China Rockfish (Sebastes nebulosus), Quillback Rockfish (S. maliger), and Copper Rockfish (S. caurinus) at Redfish Rocks, Oregon. Objectives were to (1) estimate residence times for individuals of each species, (2) evaluate spatial and temporal movement patterns, and (3) analyze the relationship between habitat attributes and movement patterns. Our results demonstrated that this small (6.78 km2) no-take marine reserve provides refuge for a substantial portion of the local population of these demersal residential fishes, due to those species’ high site fidelity to this patch of high relief rocky reef habitat located within the Redfish Rocks Marine Reserve. Title: Movement Patterns of Rockfishes at the Redfish Rocks Marine Reserve, Oregon Author: Calvanese, Thomas P. The effects of Marine protected areas (MPAs) on adult fish populations depend on the degree of protection provided, which is partly a function of MPA size and the spatial extent of fish movements. The Redfish Rocks Marine Reserve (RRMR) and MPA, located on the south coast of Oregon near Port Orford, went into effect on January 1, 2012. The boundaries of the RRMR were informed by the experience of local fishermen, but without explicit knowledge of the movement patterns of individual fish. One of the intended effects of this reserve was to provide protection for Pacific rockfishes that had been targeted there by the live fish fishery. We conducted a 17- month acoustic telemetry study to document the movement patterns of 20 individuals (6-7 each) of China Rockfish (Sebastes nebulosus), Quillback Rockfish (S. maliger), and Copper Rockfish (S. caurinus) at Redfish Rocks, Oregon. Objectives were to (1) estimate residence times for individuals of each species, (2) evaluate spatial and temporal movement patterns, and (3) analyze the relationship between habitat attributes and movement patterns. Our results demonstrated that this small (6.78 km2) no-take marine reserve provides refuge for a substantial portion of the local population of these demersal residential fishes, due to those species’ high site fidelity to this patch of high relief rocky reef habitat located within the Redfish Rocks Marine Reserve. Close

• 685. [Article] Final Report 1994-1997: Effects of Fire, Mowing, and Mowing with Herbicide on Native Prairie of Baskett Butte, Baskett Slough NWR

  We report results from a field experiment evaluating the effectiveness of mowing, mowing and herbicides, and burning on woody plants, key native and non-native grasses and forbs, and the Fender’s blue ...

  Citation × Citation Citation Abstract Copy Title: Final Report 1994-1997: Effects of Fire, Mowing, and Mowing with Herbicide on Native Prairie of Baskett Butte, Baskett Slough NWR Author: Wilson, Mark V., Clark, Deborah Louise, 1950- We report results from a field experiment evaluating the effectiveness of mowing, mowing and herbicides, and burning on woody plants, key native and non-native grasses and forbs, and the Fender’s blue butterfly. The goal was to find a technique that controlled woody pest plants without harming native species or promoting non-native species. Three years after the initial manipulations, all treatments significantly reduced woody plant cover. Mowing promoted the group of measured native grasses without promoting non-native species. In contrast, burning had mixed effects on herbaceous species, promoting growth for some species and decreasing growth for others. Each treatment, particularly mowing, caused local increases in numbers of Fender’s blue butterfly egg masses, probably because lupines invigorated by treatments attracted ovipositing females. Although prescribed burning seemed to kill larvae, treated areas still accumulated more eggs masses than in controls. Three years after the start of manipulations, mowing was the most effective overall treatment for controlling woody plants, increasing native species abundance without promoting non-native species, and increasing Fender’s blue butterfly numbers. We recommend mowing for restoring similar habitats. Prescribed burning would also be an effective choice for habitat restoration. Title: Final Report 1994-1997: Effects of Fire, Mowing, and Mowing with Herbicide on Native Prairie of Baskett Butte, Baskett Slough NWR Author: Wilson, Mark V., Clark, Deborah Louise, 1950- We report results from a field experiment evaluating the effectiveness of mowing, mowing and herbicides, and burning on woody plants, key native and non-native grasses and forbs, and the Fender’s blue butterfly. The goal was to find a technique that controlled woody pest plants without harming native species or promoting non-native species. Three years after the initial manipulations, all treatments significantly reduced woody plant cover. Mowing promoted the group of measured native grasses without promoting non-native species. In contrast, burning had mixed effects on herbaceous species, promoting growth for some species and decreasing growth for others. Each treatment, particularly mowing, caused local increases in numbers of Fender’s blue butterfly egg masses, probably because lupines invigorated by treatments attracted ovipositing females. Although prescribed burning seemed to kill larvae, treated areas still accumulated more eggs masses than in controls. Three years after the start of manipulations, mowing was the most effective overall treatment for controlling woody plants, increasing native species abundance without promoting non-native species, and increasing Fender’s blue butterfly numbers. We recommend mowing for restoring similar habitats. Prescribed burning would also be an effective choice for habitat restoration. Close

• 686. [Article] Seasonal distribution and habitat selection by the redside shiner, Richardsonius balteatus, in a small Oregon stream

  Seasonal habitat availability, utilization, and selection by young of the year (< 25 mm) and adult (>25 mm) redside shiner, Richardsonius balteatus, were studied for 1 year in sections of Greasy Creek, ...

  Citation × Citation Citation Abstract Copy Title: Seasonal distribution and habitat selection by the redside shiner, Richardsonius balteatus, in a small Oregon stream Author: Rodnick, Kenneth J. Seasonal habitat availability, utilization, and selection by young of the year (< 25 mm) and adult (>25 mm) redside shiner, Richardsonius balteatus, were studied for 1 year in sections of Greasy Creek, Benton County, Oregon. Intensive stream mapping procedures and snorkling observations provided most of the quantitative measures for habitat availability and utilization respectively. A multivariate discriminant analysis and classification suggested spatial segregation of young of the year and adult redside shiners along gradients of water velocity and depth of the water column. Throughout the year, young redside shiners occupied shallower water than adults and utilized areas with lower mean water velocities. Associated with increased winter stream flows and lowered water temperatures (< 10° C), redside shiners were inactive and found in habitats offering the most cover and refuge from current. Overwintering areas populated by redside shiners included undercut banks, root wads, bank failures, fallen trees, and backwaters. During the transitional period between winter and summer, adult redside shiners shifted from overwintering habitats to the faster water of the main channel. Activities related to spawning and aggressive defense of space accompanied this shift. Young redside shiners continued to utilize protected margins. A multivariate discriminant analysis and classification comparing available and utilized stream habitats provided indices of habitat selection. Both young of the year and adult redside shiners were relatively selective in the stream habitats they utilized. The importance of four physical components (depth, current velocity, substrate composition, and cover forms) varied seasonally and with the life stage considered. Similar patterns of habitat utilization for redside shiners were observed in four larger streams and rivers. The availability of large, deep pools was important, new habitat for both young and adult redside shiners during periods of reduced stream flow in larger streams and rivers. Title: Seasonal distribution and habitat selection by the redside shiner, Richardsonius balteatus, in a small Oregon stream Author: Rodnick, Kenneth J. Seasonal habitat availability, utilization, and selection by young of the year (< 25 mm) and adult (>25 mm) redside shiner, Richardsonius balteatus, were studied for 1 year in sections of Greasy Creek, Benton County, Oregon. Intensive stream mapping procedures and snorkling observations provided most of the quantitative measures for habitat availability and utilization respectively. A multivariate discriminant analysis and classification suggested spatial segregation of young of the year and adult redside shiners along gradients of water velocity and depth of the water column. Throughout the year, young redside shiners occupied shallower water than adults and utilized areas with lower mean water velocities. Associated with increased winter stream flows and lowered water temperatures (< 10° C), redside shiners were inactive and found in habitats offering the most cover and refuge from current. Overwintering areas populated by redside shiners included undercut banks, root wads, bank failures, fallen trees, and backwaters. During the transitional period between winter and summer, adult redside shiners shifted from overwintering habitats to the faster water of the main channel. Activities related to spawning and aggressive defense of space accompanied this shift. Young redside shiners continued to utilize protected margins. A multivariate discriminant analysis and classification comparing available and utilized stream habitats provided indices of habitat selection. Both young of the year and adult redside shiners were relatively selective in the stream habitats they utilized. The importance of four physical components (depth, current velocity, substrate composition, and cover forms) varied seasonally and with the life stage considered. Similar patterns of habitat utilization for redside shiners were observed in four larger streams and rivers. The availability of large, deep pools was important, new habitat for both young and adult redside shiners during periods of reduced stream flow in larger streams and rivers. Close

• 687. [Article] Comparative ecology of bobwhite and scaled quail in southern Texas

  For my research goals I addressed the theoretical importance of competition in habitat selection of 2 quails and examined the use of resources in peripheral and core areas. Methodological objectives were ...

  Citation × Citation Citation Abstract Copy Title: Comparative ecology of bobwhite and scaled quail in southern Texas Author: Wilson, Marcia H. For my research goals I addressed the theoretical importance of competition in habitat selection of 2 quails and examined the use of resources in peripheral and core areas. Methodological objectives were to determine cover and food selection of Texas bobwhite (Colinus virginianus texanus) and chestnut-bellied scaled quail (Callipepla squamata castanogastris) in southern Texas. The Welder Refuge was the core area for bobwhites. The Chaparrosa and Experiment Ranches were peripheral areas for both quails. The core population for scaled quail was located at the Killam Ranch. Available cover formed a gradient from Welder to Killam. The highest percentage of herbaceous material was on Welder, whereas the largest amount of bare ground and shrub cover was at Killam. Bobwhites and scaled quail used and preferred different cover types. Bobwhites selected dense herbaceous material, whereas scaled quail preferred sparse vegetation and a shrub overstory. Based on niche breadth estimates, both quails used a narrow range of cover types in their respective core areas and a broad range in the peripheral areas. The frequency of available food items also formed a gradient. Welder had the largest percent frequency of animal matter and of herbaceous seeds and green leaves. Killam had the highest frequency of seeds, leaves, and fleshy fruits from woody plants. Bobwhites preferred grass seeds and animal matter, whereas scaled quail selected the fruits and seeds of woody plants. Niche breadth estimates were relatively constant for each quail. Theoretically, when intraspecific competition is most intense a species selects a broad range of habitats, whereas sympatric species occupy a narrow range of resources due to interspecific competition. However, when I used niche breadth estimates to address my first goal, neither component of the habitat (cover or food) followed the anticipated pattern. Therefore, I believe competition is not the major selective force in habitat selection of quails. The generalization has been put forth that in the peripheral part of a range birds occupy their optimal habitat, whereas at the center of the range, optimal and suboptimal habitats are used. However, the core area contains an abundance of preferred habitat and a species is able to meet its life-history requirements within a narrow range of cover types. Peripheral areas supply only suboptimal habitat and in order to fulfill the species-specific needs a species must use a wide range of cover types. Title: Comparative ecology of bobwhite and scaled quail in southern Texas Author: Wilson, Marcia H. For my research goals I addressed the theoretical importance of competition in habitat selection of 2 quails and examined the use of resources in peripheral and core areas. Methodological objectives were to determine cover and food selection of Texas bobwhite (Colinus virginianus texanus) and chestnut-bellied scaled quail (Callipepla squamata castanogastris) in southern Texas. The Welder Refuge was the core area for bobwhites. The Chaparrosa and Experiment Ranches were peripheral areas for both quails. The core population for scaled quail was located at the Killam Ranch. Available cover formed a gradient from Welder to Killam. The highest percentage of herbaceous material was on Welder, whereas the largest amount of bare ground and shrub cover was at Killam. Bobwhites and scaled quail used and preferred different cover types. Bobwhites selected dense herbaceous material, whereas scaled quail preferred sparse vegetation and a shrub overstory. Based on niche breadth estimates, both quails used a narrow range of cover types in their respective core areas and a broad range in the peripheral areas. The frequency of available food items also formed a gradient. Welder had the largest percent frequency of animal matter and of herbaceous seeds and green leaves. Killam had the highest frequency of seeds, leaves, and fleshy fruits from woody plants. Bobwhites preferred grass seeds and animal matter, whereas scaled quail selected the fruits and seeds of woody plants. Niche breadth estimates were relatively constant for each quail. Theoretically, when intraspecific competition is most intense a species selects a broad range of habitats, whereas sympatric species occupy a narrow range of resources due to interspecific competition. However, when I used niche breadth estimates to address my first goal, neither component of the habitat (cover or food) followed the anticipated pattern. Therefore, I believe competition is not the major selective force in habitat selection of quails. The generalization has been put forth that in the peripheral part of a range birds occupy their optimal habitat, whereas at the center of the range, optimal and suboptimal habitats are used. However, the core area contains an abundance of preferred habitat and a species is able to meet its life-history requirements within a narrow range of cover types. Peripheral areas supply only suboptimal habitat and in order to fulfill the species-specific needs a species must use a wide range of cover types. Close

• 688. [Article] Habitat factors affecting pronghorn use of playas in south central Oregon

  Pronghorn (Antilocapra americana) use of four playas (intermittent lakebeds) on Hart Mountain National Antelope Refuge (NAR) in south central Oregon was studied during the summers of 1974 and 1975. Percent ...

  Citation × Citation Citation Abstract Copy Title: Habitat factors affecting pronghorn use of playas in south central Oregon Author: Good, James Ronald Pronghorn (Antilocapra americana) use of four playas (intermittent lakebeds) on Hart Mountain National Antelope Refuge (NAR) in south central Oregon was studied during the summers of 1974 and 1975. Percent canopy cover of playa vegetation, plant phenology, percent desiccated vegetation, soil moisture, available surface water and pronghorn use of range sites adjacent to playas were measured for each study area; the relationship between these parameters and pronghorn use of each lakebed was determined. A total of 14,316 pronghorn observations was recorded on the four playas during the two summers. Pronghorn observations totalled 4510 on range sites adjacent to the playas. Desert Lake received significantly (P < 0.01) more pronghorn use than the other playas during 1974 and 1975. No significant differences in use existed among Dobyns, Long and Spanish Lakes during either study year. Pronghorns demonstrated a greater dependence on lakebeds during a dry year than during a wet year. The importance of succulent vegetation to pronghorns was reflected in the relationship between soil moisture and pronghorn use. Pronghorns indicated a strong preference for leafy arnica (Arnica foliosa), particularly at Desert Lake. On Spanish Lake during the wet year, 1975, prostrate knotweed (Polygonum aviculare) was an important pronghorn food. Other forbs eaten by pronghorns were poverty sumpweed (Iva axillaris) and Oenothera flava. As soil moisture decreased, desiccation of vegetation increased, and pronghorn use on playas increased, primarily on Desert Lake where the lowest percent desiccated vegetation occurred. Early leaf growth and early flowering stages of forbs were the most important developmental stages causing a selective response by pronghorns. Pronghorns terminated use of a lakebed if drinking water was unavailable, but the mere presence of water on a playa did not insure use. As upland range sites, dominated by low sagebrush (Artemisia arbuscula), dried, pronghorn use of playas intensified throughout summer and early fall. Patterns of use by pronghorns of range sites adjacent to playas were similar between years, but increased pronghorn use during the wet year on all sites except Desert Lake supported the idea that during the wet year pronghorns were less dependent on playa vegetation. At Desert Lake, pronghorns indicated a preference for the Intermittent Lake (fair condition) range site, dominated by Bolander's silver sagebrush (A. cana bolanderi). At the other three lakebeds, pronghorns showed a preference for Rocky Terrace (poor condition) range site. Pronghorns appeared to prefer the Desert Lake study site because of the combination of habitat factors which the other three playa sites lacked. Title: Habitat factors affecting pronghorn use of playas in south central Oregon Author: Good, James Ronald Pronghorn (Antilocapra americana) use of four playas (intermittent lakebeds) on Hart Mountain National Antelope Refuge (NAR) in south central Oregon was studied during the summers of 1974 and 1975. Percent canopy cover of playa vegetation, plant phenology, percent desiccated vegetation, soil moisture, available surface water and pronghorn use of range sites adjacent to playas were measured for each study area; the relationship between these parameters and pronghorn use of each lakebed was determined. A total of 14,316 pronghorn observations was recorded on the four playas during the two summers. Pronghorn observations totalled 4510 on range sites adjacent to the playas. Desert Lake received significantly (P < 0.01) more pronghorn use than the other playas during 1974 and 1975. No significant differences in use existed among Dobyns, Long and Spanish Lakes during either study year. Pronghorns demonstrated a greater dependence on lakebeds during a dry year than during a wet year. The importance of succulent vegetation to pronghorns was reflected in the relationship between soil moisture and pronghorn use. Pronghorns indicated a strong preference for leafy arnica (Arnica foliosa), particularly at Desert Lake. On Spanish Lake during the wet year, 1975, prostrate knotweed (Polygonum aviculare) was an important pronghorn food. Other forbs eaten by pronghorns were poverty sumpweed (Iva axillaris) and Oenothera flava. As soil moisture decreased, desiccation of vegetation increased, and pronghorn use on playas increased, primarily on Desert Lake where the lowest percent desiccated vegetation occurred. Early leaf growth and early flowering stages of forbs were the most important developmental stages causing a selective response by pronghorns. Pronghorns terminated use of a lakebed if drinking water was unavailable, but the mere presence of water on a playa did not insure use. As upland range sites, dominated by low sagebrush (Artemisia arbuscula), dried, pronghorn use of playas intensified throughout summer and early fall. Patterns of use by pronghorns of range sites adjacent to playas were similar between years, but increased pronghorn use during the wet year on all sites except Desert Lake supported the idea that during the wet year pronghorns were less dependent on playa vegetation. At Desert Lake, pronghorns indicated a preference for the Intermittent Lake (fair condition) range site, dominated by Bolander's silver sagebrush (A. cana bolanderi). At the other three lakebeds, pronghorns showed a preference for Rocky Terrace (poor condition) range site. Pronghorns appeared to prefer the Desert Lake study site because of the combination of habitat factors which the other three playa sites lacked. Close

• 689. [Article] Cool, pathogen free refuge lowers pathogen associated prespawn mortality of Willamette River Chinook salmon (Oncorhynchus tshawytscha)

  Spring Chinook salmon, Oncorhynchus tshawytscha, are transported above dams in the Willamette River to provide access to blocked spawning habitat. However, 30-95% of these transplants may die before spawning ...

  Citation × Citation Citation Abstract Copy Title: Cool, pathogen free refuge lowers pathogen associated prespawn mortality of Willamette River Chinook salmon (Oncorhynchus tshawytscha) Author: Benda, Susan (Susan Eileen) Spring Chinook salmon, Oncorhynchus tshawytscha, are transported above dams in the Willamette River to provide access to blocked spawning habitat. However, 30-95% of these transplants may die before spawning in some years. To varying degrees, salmon in other tributaries--both blocked and unblocked--have similar prespawn mortality (PSM). Our study determined if holding in constant temperature, pathogen free conditions prior to spawning increased survival to spawn. In addition, we evaluated pathogens as a potential cause of PSM. Adult Chinook were captured early and late in the season from the lower Willamette River and from upper river tributaries and held in constant, cool temperature (13 ˚C), pathogen-free water at Oregon State University. Additional fish were sampled at time of transport from each of the collection sites. Finally, recent mortalities were collected from river surveys on holding and spawning reaches above traps. Necropsies were performed on all fish, and samples were processed for histology. Held fish were spawned to determine if progeny were viable. Held fish were less likely to be a PSM than fish that were outplanted to the river. However, bacterial infections were more prevalent in held fish than outplanted fish. Consistent with these observations, PSM in held fish was more likely to have higher burdens of pathogens than spawned fish. Held spawned fish were more likely to have Myxobolus sp. brain infections and less likely to be infected with the kidney myxozoan Parvicapusla minibicornis than spawned outplanted fish. The equal likelihood of other pathogens for held and outplanted spawned fish suggests interactive effects determine survival and that holding at 13 ˚C prevented expression of lethal pathogenesis. Progeny of held fish from all locations and collection dates were viable. Overall, holding could be a viable method to reduce PSM, but issues of transport stress, proliferative disease such as those caused by bacteria, and antibiotics remain. Title: Cool, pathogen free refuge lowers pathogen associated prespawn mortality of Willamette River Chinook salmon (Oncorhynchus tshawytscha) Author: Benda, Susan (Susan Eileen) Spring Chinook salmon, Oncorhynchus tshawytscha, are transported above dams in the Willamette River to provide access to blocked spawning habitat. However, 30-95% of these transplants may die before spawning in some years. To varying degrees, salmon in other tributaries--both blocked and unblocked--have similar prespawn mortality (PSM). Our study determined if holding in constant temperature, pathogen free conditions prior to spawning increased survival to spawn. In addition, we evaluated pathogens as a potential cause of PSM. Adult Chinook were captured early and late in the season from the lower Willamette River and from upper river tributaries and held in constant, cool temperature (13 ˚C), pathogen-free water at Oregon State University. Additional fish were sampled at time of transport from each of the collection sites. Finally, recent mortalities were collected from river surveys on holding and spawning reaches above traps. Necropsies were performed on all fish, and samples were processed for histology. Held fish were spawned to determine if progeny were viable. Held fish were less likely to be a PSM than fish that were outplanted to the river. However, bacterial infections were more prevalent in held fish than outplanted fish. Consistent with these observations, PSM in held fish was more likely to have higher burdens of pathogens than spawned fish. Held spawned fish were more likely to have Myxobolus sp. brain infections and less likely to be infected with the kidney myxozoan Parvicapusla minibicornis than spawned outplanted fish. The equal likelihood of other pathogens for held and outplanted spawned fish suggests interactive effects determine survival and that holding at 13 ˚C prevented expression of lethal pathogenesis. Progeny of held fish from all locations and collection dates were viable. Overall, holding could be a viable method to reduce PSM, but issues of transport stress, proliferative disease such as those caused by bacteria, and antibiotics remain. Close

• 690. [Article] An evaluation of attempts to reestablish the sea otter in Oregon

  During the summers of 1970 and 1971 a total of 95 sea otter (Enhydra lutris) were shipped to Oregon from Amchitka Island, Alaska. The 1970 shipment consisted of 31 otter which were to be released on the ...

  Citation × Citation Citation Abstract Copy Title: An evaluation of attempts to reestablish the sea otter in Oregon Author: Jameson, Ronald James During the summers of 1970 and 1971 a total of 95 sea otter (Enhydra lutris) were shipped to Oregon from Amchitka Island, Alaska. The 1970 shipment consisted of 31 otter which were to be released on the southern Oregon Coast near the town of Port Orford. Two of these animals died in holding pens and 29 were successfully released to the wild on 18 July 1970. A second shipment of 64 sea otter was divided into two groups. On 24 June 1971, 24 otter were released at Port Orford and 40 more were released near Cape Arago. Total documented mortality of the translocated sea otter consisted of eight animals, seven of these were found within 1 week of the releases. During the study period reports of sea otter were distributed from Tillamook Head to Brookings, Oregon, a distance of approximately 276 miles. A single report was received from Tolvana Beach, Oregon, 181 miles north of the nearest release site. Concentrations of otter were established at two locations during 1972, Simpson and Blanco reefs. The number of animals that could.be observed at either of these sites seemed to be related to the season, with most otter using Simpson Reef during the winter months, subsequently moving to Blanco Reef 35 miles to the south as the weather subsided. The use patterns for 1972-73 were similar to those for 1971-72; however, the number of otter using Simpson Reef during the winter of 1972-73 was less than for the previous winter, suggesting that a portion of the herd may have remained in the vicinity of Cape Blanco during winter 1972-73. It is estimated that 30-35 sea otter were on the coast at the termination of this study (5 October 1973). The first sea otter pup was sighted on 20 February 1972, 19 months after the 1970 release at Port Orford. Subsequently nine more pups were observed during the study period: three in 1972 and six in 1973. Data on food habits were gathered at Simpson Reef. Sea urchins (Strongylocentrotus spp. ) comprised the major portion of the sea otter's diet and accounted for nearly 64 percent of the total number of observations. Mollusks accounted for 14.4 percent and several species of crabs comprised 5.2 percent. Underwater surveys of 13 areas indicate that sea urchins are the most abundant macroinvertebrates normally preyed upon by sea otter. They occur at densities of up to 47 purple sea urchins (S. purpuratus) per 0.25 m2 , with red sea urchins (S. franciscanus) occurring as high as an estimated six to eight animals per 1 m2. Results of this study indicate that approximately one-third of the Oregon coastline is suitable for sea otter habitation; approximately 80 percent of the suitable area is situated along the south coast from Coos Bay to the Oregon-California border, with the remainder in the central region near the town of Newport. Both sites chosen for the translocations contain good sea otter habitat; however, because of greater probability of human-related mortality and environmental pollution and the lesser amount of contiguous sea otter habitat in the vicinity of Cape Arago than near Port Orford; the latter appears to have been the better site. It is suggested that in the future, translocated sea otter be tagged to facilitate their identification. Recommended management of the translocated otter in Oregon includes establishment of refuges, protection of the otter and their habitat, and periodic shoreline and aerial surveys to ascertain population growth and range expansion. Title: An evaluation of attempts to reestablish the sea otter in Oregon Author: Jameson, Ronald James During the summers of 1970 and 1971 a total of 95 sea otter (Enhydra lutris) were shipped to Oregon from Amchitka Island, Alaska. The 1970 shipment consisted of 31 otter which were to be released on the southern Oregon Coast near the town of Port Orford. Two of these animals died in holding pens and 29 were successfully released to the wild on 18 July 1970. A second shipment of 64 sea otter was divided into two groups. On 24 June 1971, 24 otter were released at Port Orford and 40 more were released near Cape Arago. Total documented mortality of the translocated sea otter consisted of eight animals, seven of these were found within 1 week of the releases. During the study period reports of sea otter were distributed from Tillamook Head to Brookings, Oregon, a distance of approximately 276 miles. A single report was received from Tolvana Beach, Oregon, 181 miles north of the nearest release site. Concentrations of otter were established at two locations during 1972, Simpson and Blanco reefs. The number of animals that could.be observed at either of these sites seemed to be related to the season, with most otter using Simpson Reef during the winter months, subsequently moving to Blanco Reef 35 miles to the south as the weather subsided. The use patterns for 1972-73 were similar to those for 1971-72; however, the number of otter using Simpson Reef during the winter of 1972-73 was less than for the previous winter, suggesting that a portion of the herd may have remained in the vicinity of Cape Blanco during winter 1972-73. It is estimated that 30-35 sea otter were on the coast at the termination of this study (5 October 1973). The first sea otter pup was sighted on 20 February 1972, 19 months after the 1970 release at Port Orford. Subsequently nine more pups were observed during the study period: three in 1972 and six in 1973. Data on food habits were gathered at Simpson Reef. Sea urchins (Strongylocentrotus spp. ) comprised the major portion of the sea otter's diet and accounted for nearly 64 percent of the total number of observations. Mollusks accounted for 14.4 percent and several species of crabs comprised 5.2 percent. Underwater surveys of 13 areas indicate that sea urchins are the most abundant macroinvertebrates normally preyed upon by sea otter. They occur at densities of up to 47 purple sea urchins (S. purpuratus) per 0.25 m2 , with red sea urchins (S. franciscanus) occurring as high as an estimated six to eight animals per 1 m2. Results of this study indicate that approximately one-third of the Oregon coastline is suitable for sea otter habitation; approximately 80 percent of the suitable area is situated along the south coast from Coos Bay to the Oregon-California border, with the remainder in the central region near the town of Newport. Both sites chosen for the translocations contain good sea otter habitat; however, because of greater probability of human-related mortality and environmental pollution and the lesser amount of contiguous sea otter habitat in the vicinity of Cape Arago than near Port Orford; the latter appears to have been the better site. It is suggested that in the future, translocated sea otter be tagged to facilitate their identification. Recommended management of the translocated otter in Oregon includes establishment of refuges, protection of the otter and their habitat, and periodic shoreline and aerial surveys to ascertain population growth and range expansion. Close