25 research outputs found
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Instream cover and shade mediate avian predation on trout in semi-natural streams
Piscivory by birds can be significant, particularly on fish in small streams and during seasonal low flow when available cover from predators can be limited. Yet, how varying amounts of cover may change the extent of predation mortality from avian predators on fish is not clear. We evaluated size-selective survival of coastal cutthroat trout (Oncorhynchus clarkii clarkii) in replicated semi-natural stream sections. These sections provided high (0.01 m² of cover per m² of stream) or low (0.002 m² of cover per m² of stream) levels of instream cover available to trout and were closed to emigration. Each fish was individually tagged, allowing us to track retention of individuals during the course of the 36-day experiment, which we attributed to survival from predators, because fish had no other way to leave the streams. Although other avian predators may have been active in our system and not detected, the only predator observed was the belted kingfisher Megaceryle alcyon, which is known to prey heavily on fish. In both treatments, trout >20.4 cm were not preyed upon indicating an increased ability to prey upon on smaller individuals. Increased availability of cover improved survival of trout by 12% in high relative to low cover stream sections. Trout also survived better in stream sections with greater shade, a factor we could not control in our system. Collectively, these findings indicate that instream cover and shade from avian predators can play an important role in driving survival of fish in small streams or during periods of low flow.Keywords: body size, trout survival, piscivory, low flow, refuge, experimentKeywords: body size, trout survival, piscivory, low flow, refuge, experimen
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The role of the geophysical template and environmental regimes in controlling stream-living trout populations
The importance of multiple processes and instream factors to aquatic biota has been explored extensively, but questions remain about how local spatiotemporal variability of aquatic biota is tied to environmental regimes and the geophysical template of streams. We used an individual-based trout model to explore the relative role of the geophysical template versus environmental regimes on biomass of trout (Oncorhynchus clarkii clarkii). We parameterized the model with observed data from each of the four headwater streams (their local geophysical template and environmental regime) and then ran 12 simulations where we replaced environmental regimes (stream temperature, flow, turbidity) of a given stream with values from each neighboring stream while keeping the geophysical template fixed. We also performed single-parameter sensitivity analyses on the model results from each of the four streams. Although our modeled findings show that trout biomass is most responsive to changes in the geophysical template of streams, they also reveal that biomass is restricted by available habitat during seasonal low flow, which is a product of both the stream's geophysical template and flow regime. Our modeled results suggest that differences in the geophysical template among streams render trout more or less sensitive to environmental change, emphasizing the importance of local fish-habitat relationships in streams
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Local Variability Mediates Vulnerability of Trout Populations to Land Use and Climate Change
Land use and climate change occur simultaneously around the globe. Fully understanding their separate and combined effects requires a mechanistic understanding at the local scale where their effects are ultimately realized. Here we applied an individual-based model of fish population dynamics to evaluate the role of local stream variability in modifying responses of Coastal Cutthroat Trout (Oncorhynchus clarkii clarkii) to scenarios simulating identical changes in temperature and stream flows linked to forest harvest, climate change, and their combined effects over six decades. We parameterized the model for four neighboring streams located in a forested headwater catchment in northwestern Oregon, USA with multi-year, daily measurements of stream temperature, flow, and turbidity (2007–2011), and field measurements of both instream habitat structure and three years of annual trout population estimates. Model simulations revealed that variability in habitat conditions among streams (depth, available habitat) mediated the effects of forest harvest and climate change. Net effects for most simulated trout responses were different from or less than the sum of their separate scenarios. In some cases, forest harvest countered the effects of climate change through increased summer flow. Climate change most strongly influenced trout (earlier fry emergence, reductions in biomass of older trout, increased biomass of young-of-year), but these changes did not consistently translate into reductions in biomass over time. Forest harvest, in contrast, produced fewer and less consistent responses in trout. Earlier fry emergence driven by climate change was the most consistent simulated response, whereas survival, growth, and biomass were inconsistent. Overall our findings indicate a host of local processes can strongly influence how populations respond to broad scale effects of land use and climate change
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Differential invasion success of salmonids in southern Chile: patterns and hypotheses
Biological invasions create complex ecological and societal issues worldwide. Most of the knowledge about invasions comes only from successful invaders, but less is known about which processes determine the differential success of invasions. In this review, we develop a framework to identify the main dimensions driving the success and failure of invaders, including human influences, characteristics of the invader, and biotic interactions. We apply this framework by contrasting hypotheses and available evidence to explain variability in invasion success for 12 salmonids introduced to Chile. The success of Oncorhynchus mykiss and Salmo trutta seems to be influenced by a context-specific combination of their phenotypic plasticity, low ecosystem resistance, and propagule pressure. These well-established invaders may limit the success of subsequently introduced salmonids, with the possible exception of O. tshawytscha, which has a short freshwater residency and limited spatial overlap with trout. Although propagule pressure is high for O. kisutch and S. salar due to their intensive use in aquaculture, their lack of success in Chile may be explained by environmental resistance, including earlier spawning times than in their native ranges, and interactions with previously established and resident Rainbow Trout. Other salmonids have also failed to establish, and they exhibit a suite of ecological traits, environmental resistance, and limited propagule pressure that are variably associated with their lack of success. Collectively, understanding how the various drivers of invasion success interact may explain the differential success of invaders and provide key guidance for managing both positive and negative outcomes associated with their presence.Keywords: Salmonids, Biological invasions, Chile, Biotic resistance, Non-native species, Propagule pressure, Environmental resistanc
Forest biodiversity, ecosystem functioning and the provision of ecosystem services
Forests are critical habitats for biodiversity and they are also essential for the provision of a wide range of ecosystem services that are important to human well-being. There is increasing evidence that biodiversity contributes to forest ecosystem functioning and the provision of ecosystem services. Here we provide a review of forest ecosystem services including biomass production, habitat provisioning services, pollination, seed dispersal, resistance to wind storms, fire regulation and mitigation, pest regulation of native and invading insects, carbon sequestration, and cultural ecosystem services, in relation to forest type, structure and diversity. We also consider relationships between forest biodiversity and multifunctionality, and trade-offs among ecosystem services. We compare the concepts of ecosystem processes, functions and services to clarify their definitions. Our review of published studies indicates a lack of empirical studies that establish quantitative and causal relationships between forest biodiversity and many important ecosystem services. The literature is highly skewed; studies on provisioning of nutrition and energy, and on cultural services, delivered by mixed-species forests are under-represented. Planted forests offer ample opportunity for optimising their composition and diversity because replanting after harvesting is a recurring process. Planting mixed-species forests should be given more consideration as they are likely to provide a wider range of ecosystem services within the forest and for adjacent land uses. This review also serves as the introduction to this special issue of Biodiversity and Conservation on various aspects of forest biodiversity and ecosystem services
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ArismendiIvanFisheriesWildlifeDifferentialInvasionSuccess.pdf
Biological invasions create complex ecological
and societal issues worldwide. Most of the
knowledge about invasions comes only from successful
invaders, but less is known about which processes
determine the differential success of invasions. In this
review, we develop a framework to identify the main
dimensions driving the success and failure of invaders,
including human influences, characteristics of the
invader, and biotic interactions. We apply this framework
by contrasting hypotheses and available evidence
to explain variability in invasion success for 12
salmonids introduced to Chile. The success of Oncorhynchus
mykiss and Salmo trutta seems to be influenced by a context-specific combination of their
phenotypic plasticity, low ecosystem resistance, and
propagule pressure. These well-established invaders
may limit the success of subsequently introduced
salmonids, with the possible exception of O. tshawytscha,
which has a short freshwater residency and
limited spatial overlap with trout. Although propagule
pressure is high for O. kisutch and S. salar due to their
intensive use in aquaculture, their lack of success in
Chile may be explained by environmental resistance,
including earlier spawning times than in their native
ranges, and interactions with previously established
and resident Rainbow Trout. Other salmonids have
also failed to establish, and they exhibit a suite of
ecological traits, environmental resistance, and limited
propagule pressure that are variably associated
with their lack of success. Collectively, understanding how the various drivers of invasion success interact
may explain the differential success of invaders and
provide key guidance for managing both positive and
negative outcomes associated with their presence.Keywords: Biological invasions, Salmonids, Non-native species, Chile, Biotic resistance, Propagule pressure, Environmental resistanc
Recommended from our members
ArismendiIvanFisheriesWildlifeDifferentialInvasionSuccess_SupplementalMaterial1.pdf
Biological invasions create complex ecological
and societal issues worldwide. Most of the
knowledge about invasions comes only from successful
invaders, but less is known about which processes
determine the differential success of invasions. In this
review, we develop a framework to identify the main
dimensions driving the success and failure of invaders,
including human influences, characteristics of the
invader, and biotic interactions. We apply this framework
by contrasting hypotheses and available evidence
to explain variability in invasion success for 12
salmonids introduced to Chile. The success of Oncorhynchus
mykiss and Salmo trutta seems to be influenced by a context-specific combination of their
phenotypic plasticity, low ecosystem resistance, and
propagule pressure. These well-established invaders
may limit the success of subsequently introduced
salmonids, with the possible exception of O. tshawytscha,
which has a short freshwater residency and
limited spatial overlap with trout. Although propagule
pressure is high for O. kisutch and S. salar due to their
intensive use in aquaculture, their lack of success in
Chile may be explained by environmental resistance,
including earlier spawning times than in their native
ranges, and interactions with previously established
and resident Rainbow Trout. Other salmonids have
also failed to establish, and they exhibit a suite of
ecological traits, environmental resistance, and limited
propagule pressure that are variably associated
with their lack of success. Collectively, understanding how the various drivers of invasion success interact
may explain the differential success of invaders and
provide key guidance for managing both positive and
negative outcomes associated with their presence.Keywords: Environmental resistance, Chile, Salmonids, Non-native species, Propagule pressure, Biotic resistance, Biological invasion
Recommended from our members
ArismendiIvanFisheriesWildlifeDifferentialInvasionSuccess_SupplementalMaterial2.pdf
Biological invasions create complex ecological
and societal issues worldwide. Most of the
knowledge about invasions comes only from successful
invaders, but less is known about which processes
determine the differential success of invasions. In this
review, we develop a framework to identify the main
dimensions driving the success and failure of invaders,
including human influences, characteristics of the
invader, and biotic interactions. We apply this framework
by contrasting hypotheses and available evidence
to explain variability in invasion success for 12
salmonids introduced to Chile. The success of Oncorhynchus
mykiss and Salmo trutta seems to be influenced by a context-specific combination of their
phenotypic plasticity, low ecosystem resistance, and
propagule pressure. These well-established invaders
may limit the success of subsequently introduced
salmonids, with the possible exception of O. tshawytscha,
which has a short freshwater residency and
limited spatial overlap with trout. Although propagule
pressure is high for O. kisutch and S. salar due to their
intensive use in aquaculture, their lack of success in
Chile may be explained by environmental resistance,
including earlier spawning times than in their native
ranges, and interactions with previously established
and resident Rainbow Trout. Other salmonids have
also failed to establish, and they exhibit a suite of
ecological traits, environmental resistance, and limited
propagule pressure that are variably associated
with their lack of success. Collectively, understanding how the various drivers of invasion success interact
may explain the differential success of invaders and
provide key guidance for managing both positive and
negative outcomes associated with their presence.Keywords: Salmonids, Biotic resistance, Environmental resistance, Propagule pressure, Biological invasions, Chile, Non-native specie