Comparative Evaluation of Pacific Giant Salamander and Steelhead Trout Populations Among Streams in Old-growth and Second-growth Forests of Northwest California PDF Download
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Author: Edward John Connor
Publisher:
ISBN:
Category :
Languages : en
Pages : 494
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Author: Edward John Connor
Publisher:
ISBN:
Category :
Languages : en
Pages : 494
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Author: Michael Roy Lau
Publisher:
ISBN:
Category :
Languages : en
Pages : 128
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Author: David E. Rundio
Publisher:
ISBN:
Category : Cutthroat trout
Languages : en
Pages : 192
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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.
Author: California. Department of Fish and Game. Advisory Committee on Salmon and Steelhead Trout
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ISBN:
Category : Rainbow trout fishing
Languages : en
Pages : 42
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Author: California. Advisory Committee on Salmon and Steelhead Trout
Publisher:
ISBN:
Category : Pacific salmon
Languages : en
Pages : 64
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Author: California. Department of Fish and Game
Publisher:
ISBN:
Category : Rainbow trout
Languages : en
Pages : 76
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Author: Keith D. Underwood
Publisher:
ISBN:
Category : Bull trout
Languages : en
Pages : 173
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"The goal of this two year study was to determine if supplementation with hatchery reared steelhead trout (Oncorhynchus mykiss) and spring chinook salmon (0. tshawytscha) negatively impacted wild native bull trout (Salvelinus confluentus) through competitive interactions. Four streams with varying levels of supplementation activity were sampled in Southeast Washington: Mill Creek, Tucannon River, Wolf Fork and Asotin Creek. Mill Creek was not supplemented with hatchery reared fish. The Tucannon River was intensely supplemented with hatchery reared steelhead smolts, rainbow trout and spring chinook salmon smolts. Wolf Fork was indirectly supplemented with hatchery reared steelhead smolts by releasing smolts at the mouth of the stream. Asotin Creek was supplemented for three years in the mid-1980's with hatchery reared steelhead smolts. Sampling in Asotin Creek was discontinued after the first year of study because too few bull trout were collected for analysis (n = 1). Tasks performed during this study were population density, relative abundance, microhabitat utilization, habitat availability, diet analysis, bull trout spawning ground surveys, radio telemetry of adult bull trout, and growth analysis. The data were used to identify the extent of geographic overlap among species and resources utilized by each species. This information was compared among stream populations and among species within a stream to identify changes in behavior that resulted from supplementation activities. We found that bull trout overlapped geographically with the supplemented species in each of the study streams suggesting competition among species was possible. Within a stream, bull trout and the supplemented species utilized dissimilar microhabitats. Among streams, microhabitat utilization by species was similar suggesting that supplementation activities had not resulted in a shift in habitat utilization. The diet of bull trout and O. mykiss significantly overlapped in each of the study streams, however, food was abundant and did not appear to be a limited resource. Age at length and back- calculated lengths identified differences in growth among bull trout and steelhead populations. The stream most intensely supplemented contained bull trout with the slowest growth and the non-supplemented stream contained bull trout with the fastest growth. Conversely, the stream most intensely supplemented contain O. myksis with the fastest growth and the non-supplemented stream contained O. mykisis with the slowest growth. Growth indicated that bull trout may have been negatively impacted from supplementation, although, other factors such as stream temperature may have contributed to the difference in growth. Condition factor among stream populations did not differ suggesting that the ability of each fish species to add weight as length increased was the same among stream populations. At current population levels, and current habitat quantity and quality, I detected no impacts to bull trout as a result of supplementation with hatchery reared O. mykiss trout and spring chinook salmon"--Document.
Author: Brooke E. Penaluna
Publisher:
ISBN:
Category : Coastal cutthroat trout
Languages : en
Pages : 109
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Studies of the effects of forest harvest on streams and fish have a long history in the Pacific Northwest. Results of this work have prompted development of new forest harvest practices that are more protective of these resources, but the effectiveness of these new practices has not been fully evaluated. Furthermore, the effects of contemporary forest harvest in the context of climate change are poorly understood. To address these issues, my overall research goal was to understand how water quality, water quantity, and instream habitat influence individuals and corresponding population dynamics of coastal cutthroat trout (Oncorhynchus clarkii clarkii). My work was designed to complement field results from a new generation of watershed studies currently underway in western Oregon. I combined semi-natural experiments with modeling based on field observations to understand fundamental causes and processes influencing trout. This multifaceted approach provided a novel process-based perspective on issues related to forest harvest and climate. In Chapter 2, I evaluated individual- and population-level responses of coastal cutthroat trout to instream cover. Although the influences of forest harvest on stream flow, temperature, and turbidity are often the focus, instream cover may be strongly influenced by forest harvest. In addition, restoration of instream cover is now a common practice, but the importance of cover itself to stream-living fishes is still a major question. To address this issue, I conducted large-scale manipulative experiments in outdoor semi-natural stream units to approximate conditions experienced by trout in headwater streams in western Oregon. I determined that infrequent cover use by trout leads to emigration. Next, I built upon key ideas within stream ecology related to the importance of location within a landscape to aquatic biota, which have been explored and debated extensively. The variability in population responses across similar locations within a landscape is less understood. My objective in Chapter 3 was to understand the variability in population biomass of coastal cutthroat trout across headwater streams by understanding of the relative roles of two general classes of variables that occur in headwater streams: dynamic environmental regimes and relatively fixed habitat structure. I provided evidence that environmental regimes contribute to biomass variability while also being constrained by the habitat structure, given the range of conditions that I was able to simulate. Although the effects of contemporary forest harvest and climate change occur simultaneously, they are not typically considered together, as they are in Chapter 4. Here, I tracked population responses of trout, including biomass, survival, growth, and timing of emergence during six decades across four modeled headwater streams using the same individual-based trout model as in Chapter 3. I modeled four scenarios: 1) baseline conditions (simulation of existing conditions); 2) effects of contemporary forest harvest; 3) effects of climate change; and 4) the combined effects of forest harvest and climate change. Differences among scenarios were tied to changes in flow and temperature regimes. Here, I found that there was a high degree of local variability in the responses that I simulated. Whereas localized responses to forest harvest have been observed, my findings contrast with the vast majority of work on species responses to climate change, most of which reports relatively synchronous or uniform responses. I highlighted the role of individual variability of trout and local variability of streams, which ultimately suggest that some individuals and populations of trout may be more vulnerable than others to the effects of forest harvest, climate change, or both processes together.
Author: David H. Johnson
Publisher:
ISBN:
Category : Nature
Languages : en
Pages : 764
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Book Description
This volume provides information about the terrestrial, freshwater, and marine habitats of Oregon and Washington and the wildlife that depend upon them; it also supports broader and more consistent conservation planning, management, and research. The 27 chapters identify 593 wildlife species, define some 300 wildlife terms, profile wildlife communities, review introduced and extirpated species and species at risk, and discuss management approaches. The volume includes color and bandw photographs, maps, diagrams, and illustrations; and the accompanying CD-ROM contains additional wildlife data (60,000 records), maps, and seven matrixes that link wildlife species with their respective habitat types. Johnson is a wildlife biologist, engineer, and habitat scientist; and O'Neill is director of the Northwest Habitat Institute; they worked together on this publication project as its managing directors. Annotation copyrighted by Book News Inc., Portland, OR
Author:
Publisher:
ISBN:
Category : Biogeography
Languages : en
Pages : 92
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Book Description
This volume represents a first attempt at holistically classifying and mapping ecological regions across all three countries of the North American continent. A common analytical methodology is used to examine North American ecology at multiple scales, from large continental ecosystems to subdivisions of these that correlate more detailed physical and biological settings with human activities on two levels of successively smaller units. The volume begins with an overview of North America from an ecological perspective, concepts of ecological regionalization. This is followed by descriptions of the 15 broad ecological regions, including information on physical and biological setting and human activities. The final section presents case studies in applications of the ecological characterization methodology to environmental issues. The appendix includes a list of common and scientific names of selected species characteristic of the ecological regions.
