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Local extirpations of Pacific salmon Oncorhynchus spp. and steelhead O. mykiss, often due to dams and other stream barriers, are common throughout the western United States. Reestablishing salmonid populations in areas they historically occupied has substantial potential to assist conservation efforts, but best practices for reintroduction are not well established. In this paper, we present a framework for planning reintroductions designed to promote the recovery of salmonids listed under the Endangered Species Act. Before implementing a plan, managers should first describe the benefits, risks, and constraints of a proposed reintroduction. We define benefits as specific biological improvements towards recovery objectives. Risks are the potential negative outcomes of reintroductions that could worsen conservation status rather than improve it. Constraints are biological factors that will determine whether the reintroduction successfully establishes a self-sustaining population. We provide guidance ...

Major ecological realignments are already occurring in response to climate change. To be successful, conservation strategies now need to account for geographical patterns in traits sensitive to climate change, as well as climate threats to species-level diversity. As part of an effort to provide such information, we conducted a climate vulnerability assessment that included all anadromous Pacific salmon and steelhead (Oncorhynchus spp.) population units listed under the U.S. Endangered Species Act. Using an expert-based scoring system, we ranked 20 attributes for the 28 listed units and 5 additional units. Attributes captured biological sensitivity, or the strength of linkages between each listing unit and the present climate; climate exposure, or the magnitude of projected change in local environmental conditions; and adaptive capacity, or the ability to modify phenotypes to cope with new climatic conditions. Each listing unit was then assigned one of four vulnerability categories. Units ranked most vulnerable overall were Chinook (O. tshawytscha) in the California Central Valley, coho (O. kisutch) in California and southern Oregon, sockeye (O. nerka) in the Snake River Basin, and spring-run Chinook in the interior Columbia and Willamette River Basins. We identified units with similar vulnerability profiles using a hierarchical cluster analysis. Life history characteristics, especially freshwater and estuary residence times, interplayed with gradations in exposure from south to north and from coastal to interior regions to generate landscape-level patterns within each species. Nearly all listing units faced high exposures to projected increases in stream temperature, sea surface temperature, and ocean acidification, but other aspects of exposure peaked in particular regions. Anthropogenic factors, especially migration barriers, habitat degradation, and hatchery influence, have reduced the adaptive capacity of most steelhead and salmon populations. Enhancing adaptive capacity is essential to mitigate for the increasing threat of climate change. Collectively, these results provide a framework to support recovery planning that considers climate impacts on the majority of West Coast anadromous salmonids.

This study considered whether different population viability analyses give similar estimates of extinction risk across management contexts. We compared the performance of population viability analyses developed by numerous scientific teams to estimate extinction risk of anadromous Pacific salmonids listed under the U.S. Endangered Species Act and challenged each analysis with data from 34 populations. We found variation in estimated extinction risk among analytical techniques, which was driven by varying model assumptions and the inherent uncertainty of risk forecasts. This result indicates that the scientific teams developed techniques that perform differently. We recommend that managers minimize uncertainty in risk estimates by using multiple models tailored to the local ecology. Assessment of relative extinction risk was less sensitive to model assumptions than was assessment of absolute extinction risk. Thus, the former method is better for comparing population status and raises caution about...

We developed an intrinsic potential (IP) model to estimate the potential of streams to provide habitat for spawning fall Chinook salmon (Oncorhynchus tshawytscha) in the Lower Columbia River evolutionarily significant unit. This evolutionarily significant unit is a threatened species, and both fish abundance and distribution are reduced from historical levels. The IP model focuses on geomorphic conditions that lead to the development of a habitat that fish use and includes three geomorphic channel parameters: confinement, width and gradient. We found that the amount of potential habitat for each population does not correlate with current, depressed, total population abundance. However, reaches currently used by spawners have high IP, and IP model results correlate well with results from the complex Ecosystem Diagnosis and Treatment model. A disproportionately large amount of habitat with the best potential is currently inaccessible to fish because of anthropogenic barriers. Sensitivity analyses indicate that uncertainty in the relationship between channel width and habitat suitability has the largest influence on model results and that model form influences model results more for some populations than for others. Published in 2011 by John Wiley & Sons, Ltd.

SUMMARY 1. A key element of conservation planning is the extremely challenging task of estimating the likely effect of restoration actions on population status. To compare the relative benefits of typical habitat restoration actions on Pacific salmon (Oncorhynchus spp.), we modelled the response of an endangered Columbia River Chinook salmon (O. tshawytscha) population to changes in habitat characteristics either targeted for restoration or with the potential to be degraded. 2. We applied a spatially explicit, multiple life stage, Beverton-Holt model to evaluate how a set of habitat variables with an empirical influence on spring-run Chinook salmon survivorship influenced fish population abundance, productivity, spatial structure and diversity. Using habitat condition scenarios – historical conditions and future conditions with restoration, no restoration, and degradation – we asked the following questions: (i) how is population status affected by alternative scenarios of habitat change, (ii) which individual habitat characteristics have the potential to substantially influence population status and (iii) which life stages have the largest impact on population status? 3. The difference in population abundance and productivities resulting from changes in modelled habitat variables from the ‘historical’ to ‘current’ scenarios suggests that there is substantial potential for improving population status. Planned restoration actions directed toward modelled variables, however, produced only modest improvements. 4. The model predicted that population status could be improved by additional restoration efforts directed toward further reductions in the percentage of fine sediments in the streambed, a factor that has a large influence on egg survival. Actions reducing fines were predicted to be especially effective outside the national forest that covers most of the basin. Scenarios that increased capacity by opening access to habitat in good condition also had a positive but smaller effect on spawner numbers. 5. Degradation in habitat quality, particularly in percent fine sediments, within stream reaches located in the national forest had great potential to further reduce this population’s viability. This finding supports current forest planning efforts to minimise road density and clear-cut harvests and to return forest stand structure in dry regions to the historical condition that promoted frequent low-intensity fires rather than catastrophic standreplacing fires, as these landscape factors have been shown to influence percent fine sediment in streams.

Summary 1. Conservation planning is often hampered by the lack of causal quantitative links between landscape characteristics, restoration actions and habitat conditions that impact the status of imperilled species. Here we present a first step toward linking actions on the landscape to the population status of endangered stream-type Chinook salmon (Oncorhynchus tshawytscha). 2. We developed relationships between land use, landscape characteristics and freshwater habitat of spring Chinook salmon in the Wenatchee River basin. Available data allowed us to find relationships that described water temperatures at several life stages (prespawning, egg incubation and summer rearing) and substratum characteristics, including fine sediments, cobble and embeddedness. Predictors included altitude, gradient, mean annual precipitation, total and riparian forest cover, road density, impervious surface and alluvium. We used a model averaging approach to account for parameter and model selection uncertainty. Key predictors were total forest cover and impervious surface area for prespawning and summer rearing temperatures; precipitation and stream gradients were important predictors of the percent of fine sediments in stream substrata. 3. We estimated habitat conditions using these relationships in three alternative landscape scenarios: historical, no restoration and one that included a set of restoration actions from local conservation planning. We found that prespawning and summer temperatures were estimated to be slightly higher historically relative to current conditions in dry sparsely forested areas, but lower in some important Chinook salmon spawning and rearing areas and lower in those locations under the restoration scenario. Fine sediments were lower in the historical scenario and were reduced as a consequence of restoration actions in two areas currently unoccupied by Chinook salmon that contain reaches with some potential for high quality spawning and rearing. Cobble and embeddedness in general were predicted to be higher historically and changed little as a result of restoration actions relative to current conditions. 4. This modelling framework converts suites of restoration actions into changes in habitat condition, thereby enabling restoration planners to evaluate alternative combinations of proposed actions. It also provides inputs to models linking habitat conditions to population status. This approach represents a first step in estimating impacts of restoration strategies, and can provide key information for conservation managers and planners.

Most hatchery programs for anadromous salmonids have been initiated to increase the numbers of fish for harvest, to mitigate for habitat losses, or to increase abundance in populations at low abundance. However, the manner in which these programs are implemented can have significant impacts on the evolutionary trajectory and long-term viability of populations. In this paper, we review the potential benefits and risks of hatchery programs relative to the conservation of species listed under the US Endangered Species Act. To illustrate, we present the range of potential effects within a population as well as among populations of Chinook salmon (Oncorhynchus tshawytscha) where changes to major hatchery programs are being considered. We apply evolutionary considerations emerging from these examples to suggest broader principles for hatchery uses that are consistent with conservation goals. We conclude that because of the evolutionary risks posed by artificial propagation programs, they should not be viewed as a substitute for addressing other limiting factors that prevent achieving viability. At the population level, artificial propagation programs that are implemented as a short-term approach to avoid imminent extinction are more likely to achieve long-term population viability than approaches that rely on long-term supplementation. In addition, artificial propagation programs can have out-of-population impacts that should be considered in conservation planning.

Myriad human activities increasingly threaten the existence of many species. A variety of conservation interventions such as habitat restoration, protected areas, and captive breeding have been used to prevent extinctions. Evaluating the effectiveness of these interventions requires appropriate statistical methods, given the quantity and quality of available data. Historically, analysis of variance has been used with some form of predetermined before-after control-impact design to estimate the effects of large-scale experiments or conservation interventions. However, ad hoc retrospective study designs or the presence of random effects at multiple scales may preclude the use of these tools. We evaluated the effects of a large-scale supplementation program on the density of adult Chinook salmon Oncorhynchus tshawytscha from the Snake River basin in the northwestern United States currently listed under the U.S. Endangered Species Act. We analyzed 43 years of data from 22 populations, accounting for random effects across time and space using a form of Bayesian hierarchical time-series model common in analyses of financial markets. We found that varying degrees of supplementation over a period of 25 years increased the density of natural-origin adults, on average, by 0–8% relative to nonsupplementation years. Thirty-nine of the 43 year effects were at least two times larger in magnitude than the mean supplementation effect, suggesting common environmental variables play a more important role in driving interannual variability in adult density. Additional residual variation in density varied considerably across the region, but there was no systematic difference between supplemented and reference populations. Our results demonstrate the power of hierarchical Bayesian models to detect the diffuse effects of management interventions and to quantitatively describe the variability of intervention success. Nevertheless, our study could not address whether ecological factors (e.g., competition) were more important than genetic considerations (e.g., inbreeding depression) in determining the response to supplementation.

Most hatchery programs for anadromous salmonids have been initiated to increase the numbers of fish for harvest, to mitigate for habitat losses, or to increase abundance in populations at low abundance. However, the manner in which these programs are implemented can have significant impacts on the evolutionary trajectory and long-term viability of populations. In this paper, we review the potential benefits and risks of hatchery programs relative to the conservation of species listed under the US Endangered Species Act. To illustrate, we present the range of potential effects within a population as well as among populations of Chinook salmon (Oncorhynchus tshawytscha) where changes to major hatchery programs are being considered. We apply evolutionary considerations emerging from these examples to suggest broader principles for hatchery uses that are consistent with conservation goals. We conclude that because of the evolutionary risks posed by artificial propagation programs, they should not be viewed as a substitute for addressing other limiting factors that prevent achieving viability. At the population level, artificial propagation programs that are implemented as a short-term approach to avoid imminent extinction are more likely to achieve long-term population viability than approaches that rely on long-term supplementation. In addition, artificial propagation programs can have out-of-population impacts that should be considered in conservation planning.

Techniques are described which have proved successful in rearing the larvae of nine species of marine fishes in Hawaii. The results of intensive experiments on larvae of the carangid fish, Caranx mate , are presented, with emphasis on the effects of various antibiotics on bacterial populations in rearing containers and on larval survival. Microcopepods, gastropod veligers, and rotifers were found to be suitable foods for C. mate larvae, and larval survival was enhanced when the phytoplankter Chlorella was added to cultures. Four bacterial genera were identified from natural water samples and from rearing containers in culture situations. Pseudomonas was the most abundant genus, Cytophaga next most abundant, followed by Vibrio; Flavobacterium was identified but uncommon. uncommon. In sea water containing low initial numbers of bacteria, bacteria increased more rapidly and stabilized at a higher density than in sea water containing higher initial densities. Of a number of antibiotics tested, the most effective in decreasing bacteria in sea water and enhancing hatching success and larval survival were the polymyxins, penicillins, and especially erythromycin. Repeated treatments with the same antibiotic on day 3 of the experiment did not reduce bacterial density or improve larval survival, when compared with a single treatment on day 1. These results are discussed in relation to the mode of action of the antibiotics, and suggestions are made concerning profitable lines of future research.