53 research outputs found
Abundance and body condition of sculpin (Cottus spp.) in a small forest stream following recolonization by juvenile Coho Salmon (Oncorynchus kisutch)
Recolonization by native species following reintroduction can affect resident species through a variety of processes. We examined the effects of natural recolonization by coho salmon Oncorhynchus kisutch on sculpin (Cottus rhotus and Cottus gulosus), small benthic fishes, in a small forest stream in Western Washington, USA. Provision fish passage around a small dam allowed coho access to habitat, which had been inaccessible for over 100 years. We found that density (g m−2 and number m−2) was unchanged, and body condition (the slope of the relationship between length and weight) of sculpin tended to increase from before relative to a 5-year period following recolonization. The proportion of sculpin comprising the total fish assemblage decreased after coho colonization relative to before but remained stable for a 5-year period after coho reintroduction, whereas coho density increased over fivefold. Additionally, we used Akaike's information criteria to evaluate the relative importance of physical and biological variables to predict sculpin density in pool habitats during the initial coho recolonization period. Physical microhabitat variables had little support for predicting sculpin density, whereas there was a significant support for stream temperature; cutthroat trout (Oncorhynchus clarkii) density and year were the most important predictors of sculpin density. Coho density was not significant in any model. Our results indicate coho introduction and subsequent recolonization have to date had minimal individual or population level effects on sculpin, therefore demonstrating that species reintroductions into their native range can have no measurable effect on resident organisms. Published 2013. This article is a U.S. Government work and is in the public domain in the USA
Lessons from Elwha Ecosystem Restoration: Integrating science, policy, and management
After decades of debate, planning, and environmental impact studies, the largest planned dam removal project in history was conducted on the Elwha River in Washington State, USA, from 2011 to 2014. Because this was such a unique and unprecedented project, the planning, implementation, and monitoring has occurred over 30 years and required diverse expertise across multiple stakeholders. This knowledge portfolio required that individuals and organizations with different missions collaborate effectively to ensure a successful project. The story of this river, with rugged headwaters, protected wilderness, legendary and culturally important salmon runs, and two hydroelectric dams whose placement marshaled wholesale socioeconomic and ecological changes, has become an iconic saga of change, perseverance and renewal. The two dams blocked fish migrations and disrupted sediment transport for a century, disrupting the ecological structure and function of the Elwha River. Removal of the 64-m and 32-m tall dams and the release of a large portion of the 21 million cubic meters of stored reservoir sediment, has provided a living laboratory to study the patterns, processes and outcomes of dam removal across freshwater, estuarine, and marine ecosystem boundaries from multiple scientific perspectives. This collaborative multidisciplinary approach has allowed us to improve our understanding of ecosystem responses and linkages while making the Elwha River one of the best studied dam removal projects
Dam removal enables diverse juvenile life histories to emerge in threatened salmonids repopulating a heterogeneous landscape
Human stressors block, eliminate, and simplify habitat mosaics, eroding landscapes’ life history diversity and thus biological resilience. One goal of restoration is to alleviate human stressors that suppress life history diversity, but life history responses to these efforts are still coming into focus. Here, we report life history diversity emerging in threatened salmonids (Oncorhynchus spp.) repopulating the recently undammed Elwha River (WA, United States) in adjacent but environmentally distinct tributaries. The ~20 km tributaries entered the Elwha River <1 km apart, but one had a colder stream temperature regime and swifter waters due to its high, snow-dominated elevation and steep valley gradient (~3%), while the other had a warmer stream temperature regime and slower waters because it drained a lake, was at lower elevation, and had a lower stream gradient (~1.5%). Following the 2012 removal of Elwha Dam, the tributaries’ salmonids generally became more abundant and expressed diverse life histories within and among species. The warmer, low-gradient tributary produced more age-1+ coho salmon while the colder, steeper tributary produced a notably high abundance of steelhead smolts in 2020. Additionally, salmonids exiting the warmer tributary were older and possibly larger for their age class, emigrated ~25 days earlier, and included age-0 Chinook salmon that were larger. Also, assemblage composition varied among years, with the most abundant species shifting between Chinook salmon and coho salmon, while steelhead abundances generally increased but were patchy. These patterns are consistent with a newly accessible, heterogeneous landscape generating life history diversity against the backdrop of patchy recruitment as salmonids—some with considerable hatchery-origin ancestry—repopulate an extirpated landscape. Overall, dam removal appears to have promoted life history diversity, which may bolster resilience during an era of rapid environmental change and portend positive outcomes for upcoming dam removals with similar goals
Potential for ecological nonlinearities and thresholds to inform Pacific salmon management
AbstractEcology is often governed by nonlinear dynamics. Nonlinear ecological relationships can include thresholds—incremental changes in drivers that provoke disproportionately large ecological responses. Among the species that experience nonlinear and threshold dynamics are Pacific salmon (Oncorhynchus spp.). These culturally, ecologically, and economically significant fishes are in many places declining and management focal points. Often, managers can influence or react to ecological conditions that salmon experience, suggesting that nonlinearities, especially thresholds, may provide opportunities to inform decisions. However, nonlinear dynamics are not always invoked in management decisions involving salmon. Here, we review reported nonlinearities and thresholds in salmon ecology, describe potential applications that scientists and managers could develop to leverage nonlinear dynamics, and offer a path toward decisions that account for ecological nonlinearities and thresholds to improve salmon outcomes. It appears that nonlinear dynamics are not uncommon in salmon ecology and that many management arenas may potentially leverage them to enable more effective or efficient decisions. Indeed, decisions guided by nonlinearities and thresholds may be particularly desirable considering salmon management arenas are often characterized by limited resources and mounting ecological stressors, practical constraints, and conservation challenges. More broadly, many salmon systems are data‐rich and there are an extensive range of ecological contexts in which salmon are sensitive to anthropogenic decisions. Approaches developed to leverage nonlinearities in salmon ecology may serve as examples that may inform analogous approaches in other systems and taxa
Puget sound habitat status and trends monitoring program: nearshore and large river delta geospatial data and habitat status and trends monitoring metrics
The Puget Sound Habitat Status and Trends Monitoring (PSHSTM) program was developed to provide consistent salmon habitat status and trends data to support status reviews of Endangered Species Act (ESA) listed salmon populations across Puget Sound’s major population groups. Our approach primarily relies on readily available and regularly updated aerial imagery to consistently map key habitat features at a regional scale. We have developed a census-based approach to map key habitat features throughout the nearshore, large river delta, large river, and floodplain environments across Puget Sound. This presentation will focus on our mapping efforts in Puget Sound’s nearshore and large river delta environments, and the habitat status and trends metrics that will be derived from these efforts to support ESA listing reviews. In the nearshore environment, we are mapping overwater structures (e.g., docks, piers, bridges, buoys/floats, booms, aquaculture, and boat ramps), forested shoreline, and small embayment habitat features (e.g., lagoons, pocket estuaries, and blind tidal channels) for all ≈4,000 km of Puget Sound’s shoreline. In the large river delta environment, we are mapping tidal wetland areas, geomorphic delta boundaries, and channel features (e.g., distributaries and tidal channels) for all 17 large river deltas that drain into the Puget Sound, Hood Canal, and the Strait of Juan de Fuca. This census-based approach will provide a unique opportunity to develop consistent habitat status and trends metrics for habitat quantity and quality at a regional scale that can be used to inform ESA status reviews of listed salmon populations. We anticipate that the consistent regional-scale geospatial data sets developed from these efforts can be used to support a variety of other research and management needs
Planning, implementation, and monitoring Pacific salmonid recovery following the removal of two hydroelectric dams on Washington\u27s Elwha River
The removal of Elwha and Glines Canyon dams on the Elwha River is the largest existing dam removal project in the United States. Project planning, implementation, and monitoring have occurred over 30 years and has required diverse technical expertise. Because of the size and nature of the project—two high-head dams releasing massive amounts of sediment into the river, estuary, and nearshore ecosystem—the project was unprecedented and required a great deal of technical expertise to plan, execute, and monitor. The relative success of this project required effective collaboration among individuals and organizations with varying missions. Individuals with diverse technical expertise (i.e., engineering, geomorphology, hydrology, botany, wildlife, fisheries, stream ecology, ecological monitoring) have successfully collaborated to develop several technical plans ensuring dam removal was completed, while at the same time protecting a city water supply, infrastructure, and listed and unlisted salmonids in the basin. This collaboration has continued following dam removal through the implementation of a monitoring and adaptive management plan. Our monitoring strategy often uses multiple scientific methods to evaluate metrics or performance indicators to create multiple lines of evidence, reduce uncertainty, and ensure data availability. Employing such diverse methods would not have been possible without multidisciplinary and multiagency collaboration. Collaboration and extensive monitoring has allowed project partners to identify potential barriers, assess the rate and extent of recolonization, estimate abundance, life history attributes, and productivity. This collaborative multidisciplinary approach has allowed us to monitor salmonid recovery, while also improving our understanding of ecosystem response and linkages. This has resulted in the Elwha River being one of the best studied dam removal projects in history
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Trends in Developed Land Cover Adjacent to Habitat for Threatened Salmon in Puget Sound, Washington, U.S.A.
For widely distributed species at risk, such as Pacific salmon (Oncorhynchus spp.), habitat monitoring is both essential and challenging. Only recently have widespread monitoring programs been implemented for salmon habitat in the Pacific Northwest. Remote sensing data, such as Landsat images, are therefore a useful way to evaluate trends prior to the advent of species-specific habitat monitoring programs. We used annual (1986-2008) land cover maps created from Landsat images via automated algorithms (LandTrendr) to evaluate trends in developed (50-100% impervious) land cover in areas adjacent to five types of habitat utilized by Chinook salmon (O. tshawytscha) in the Puget Sound region of Washington State, U.S.A. For the region as a whole, we found significant increases in developed land cover adjacent to each of the habitat types evaluated (nearshore, estuary, mainstem channel, tributary channel, and floodplain), but the increases were small (<1% total increase from 1986 to 2008). For each habitat type, the increasing trend changed during the time series. In nearshore, mainstem, and floodplain areas, the rate of increase in developed land cover slowed in the latter portion of the time series, while the opposite occurred in estuary and tributary areas. Watersheds that were already highly developed in 1986 tended to have higher rates of development than initially less developed watersheds. Overall, our results suggest that developed land cover in areas adjacent to Puget Sound salmon habitat has increased only slightly since 1986 and that the rate of change has slowed near some key habitat types, although this has occurred within the context of a degraded baseline condition
Modeling timing and size of juvenile Chinook salmon out-migrants at three Elwha River rotary screw traps: a window into early life history post dam removal
Chinook salmon (Oncorhynchus tshawytscha) populations express diverse early life history pathways that increase habitat utilization and demographic resiliency. Extensive anthropogenic alterations to freshwater habitats along with hatchery and harvest impacts have led to marked reductions in early life history diversity across much of the species’ range. The recent removal of two Elwha River dams between 2011 and 2014 restored access to over 90% of the available habitat that had been inaccessible to Chinook salmon since the early 1900s. This provided an opportunity to investigate how renewed access to this habitat might affect life history diversity. As exotherms, egg-to-fry development, juvenile growth, and movement are influenced by water temperatures. We used spatially and temporally explicit Elwha River water temperature and Chinook salmon spawning location data, in conjunction with spawn timing, emergence, growth, and movement models, to predict observed timing and sizes of juvenile Chinook salmon captured in three rotary screw traps in the mainstem and two tributaries during four trap years. This effort allowed us to test hypotheses regarding Elwha River Chinook salmon early life history, identify potential problems with the data, and predict how emergence and growth would change with increased spawning in the upper watershed. Predicted Chinook salmon emergence timing and predicted dates that juveniles reached 65 mm differed by as much as 2 months for different river locations due to large differences in thermal regimes longitudinally in the mainstem and between tributaries. For 10 out of the 12 trap–year combinations, the model was able to replicate important characteristics of the out-migrant timing and length data collected at the three traps. However, in most cases, there were many plausible parameter combinations that performed well, and in some cases, the model predictions and observations differed. Potential problems with the data and model assumptions were identified as partial explanations for differences and provide avenues for future work. We show that juvenile out-migrant data combined with mechanistic models can improve our understanding of how differences in temperature, spawning extent, and spawn timing affect the emergence, growth, and movement of juvenile fish across diverse riverine habitats
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Anadromy and residency in steelhead and rainbow trout (Oncorhynchus mykiss): a review of the processes and patterns
Oncorhynchus mykiss form partially migratory populations with anadromous fish that undergo marine migrations and residents that complete their life cycle in fresh water. Many populations’ anadromous components are threatened or endangered, prompting interest in understanding ecological and evolutionary processes underlying anadromy and residency. In this paper, we synthesize information to better understand genetic and environmental influences on O. mykiss life histories, identify critical knowledge gaps, and suggest next steps. Anadromy and residency appear to reflect interactions among genetics, individual condition, and environmental influences. First, an increasing body of literature suggests that anadromous and resident individuals differ in the expression of genes related to growth, smoltification, and metabolism. Second, the literature supports the conditional strategy theory, where individuals adopt a life history pattern based on their conditional status relative to genetic thresholds along with ultimate effects of size and age at maturation and iteroparity. However, except for a generally positive association between residency and high lipid content plus a large attainable size in fresh water, the effects of body size and growth are inconsistent. Thus, individuals can exhibit plasticity in variable environments. Finally, patterns in anadromy and residency among and within populations suggested a wide range of possible environmental influences at different life stages, from freshwater temperature to marine survival. Although we document a number of interesting correlations, direct tests of mechanisms are scarce and little data exist on the extent of residency and anadromy. Consequently, we identified as many data gaps as conclusions, leaving ample room for future research
Glacier retreat creating new Pacific salmon habitat in western North America
Glacier retreat poses risks and benefits for species of cultural and economic importance. One
example is Pacific salmon (Oncorhynchus spp.), supporting subsistence harvests, and commercial and recreational fisheries worth billions of dollars annually. Although decreases in
summer streamflow and warming freshwater is reducing salmon habitat quality in parts of
their range, glacier retreat is creating new streams and lakes that salmon can colonize.
However, potential gains in future salmon habitat associated with glacier loss have yet to be
quantified across the range of Pacific salmon. Here we project future gains in Pacific salmon
freshwater habitat by linking a model of glacier mass change for 315 glaciers, forced by five
different Global Climate Models, with a simple model of salmon stream habitat potential
throughout the Pacific Mountain ranges of western North America. We project that by the
year 2100 glacier retreat will create 6,146 (±1,619) km of new streams accessible for colonization by Pacific salmon, of which 1,930 (±569) km have the potential to be used for
spawning and juvenile rearing, representing 0 to 27% gains within the 18 sub-regions we
studied. These findings can inform proactive management and conservation of Pacific salmon
in this era of rapid climate change.Ye
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