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Pacific lamprey Entosphenus tridentatus has an anadromous life cycle that begins with larvae that filter-feed in freshwater, followed by transformation into juveniles that migrate to the ocean where they parasitize hosts, and adults that migrate into freshwater to spawn and die. The marine-phase (i.e., juvenile life stage) is important yet poorly understood, and is associated with growth opportunities to achieve maximum body size and recruitment. The four goals of this paper are to: (1) synthesize the literature to identify patterns in the marine biology of Pacific lamprey; (2) develop hypotheses to explain these patterns; (3) identify limiting factors and threats, and (4) identify research needs. We hypothesize that recruitment of adult lamprey to spawning populations is influenced by oceanographic regimes through impacts on host abundance. Three marine factors that may be limiting lamprey abundance include: (1) predation and fisheries bycatch; (2) host availability; and (3) host contaminant loads. Four potential marine-related threats to lamprey include: (1) pollution; (2) climate change; (3) unfavorable oceanographic regimes; and (4) the effects of interactions between climate and regimes. Pacific lamprey is not philopatric and the extent to which host migrations and other factors influence lamprey entry into rivers is unclear. Research is needed to fill information gaps on how, when, why, and where lamprey move, feed, and grow in the ocean. Their widespread distribution, parasitic life history, diverse hosts, and multiple predators suggest that Pacific lamprey is integrated into diverse marine ecosystems.

An animal's performance during its early life stage can greatly influence its survival to adulthood. Therefore, understanding aspects of early life history can be informative, particularly when designing management plans to rebuild a population. For a threatened population of fall Chinook salmon (Oncorhynchus tshawytscha) in the Snake River of Idaho, we reconstructed the early life history for 124 returning wild and hatchery adults using information recorded in their otoliths. Of our sampled wild adults (n = 61), 43% and 49% reared within the Snake River and Clearwater/Salmon rivers. We also found that only 21% of our sampled wild adults exhibited the historically common subyearling out‐migration strategy, in which juveniles exit freshwater shortly after hatching, while the remaining wild adults exhibited the yearling out‐migration strategy (i.e., individuals delay their freshwater exit). As expected, yearlings had, on average, a significantly larger body size than subyearlings at ocean entry. However, 35% of wild yearlings overlapped in size with wild subyearlings suggesting that spending more time in freshwater might not necessarily result in a larger body size. Lastly, we observed that variability in fork length at Snake River egress and ocean entry were best explained by migration strategy and where it reared, followed by hatch year and sex. Results from this study highlight the utility of adult otoliths in providing details about early life history, an understanding of which is critical to the conservation of Snake River fall Chinook salmon.

Parasites transmitted through the consumption of infected prey items are commonly used to examine patterns of host feeding. However, an estimate of the prevalence of larval parasites in consumed prey items is often lacking restricting the ability to translate the number of parasites observed into the number of prey consumed. This study examined the prevalence of the nematode parasite Hysterothylacium aduncum in the benthic amphipod Americorophium salmonis recovered from the stomachs of juvenile Chinook salmon (Oncorhynchus tshawytscha) collected near the mouth of the Columbia River estuary (USA) in May, June, and July of 2011. This study represents the first estimate of the prevalence of H. aduncum in A. salmonis from this locality. The stomachs of 118 subyearling Chinook salmon were examined for prey items. We recovered 472 undigested A. salmonis from stomachs that were then examined for juvenile H. aduncum. Six of the 472 A. salmonis were infected with H. aduncum (1.3%). However, prevalence and mean intensity of H. aduncum was 74.6% and 12.9 ± 15.0 S.D. respectively in the gastrointestinal tracts of those salmon. The low prevalence of the parasite in the ingested A. salmonis and the high recovery of adult parasites in subyearling salmon suggest salmon fed on perhaps hundreds of this prey item to acquire the observed numbers of H. aduncum as opposed to the 4.0 ± 6.2 S.D. A. salmonis found on average during stomach content examination. This reemphasizes the importance of A. salmonis as a prey item for subyearling Chinook salmon within the estuary.

The Pacific Lamprey Entosphenus tridentatus, an anadromous fish native to the northern Pacific Ocean and bordering freshwater habitats, has recently experienced steep declines in abundance and range contractions along the West Coast of North America. During the early 1990s, Native American tribes recognized the declining numbers of lamprey and championed their importance. In 2012, 26 entities signed a conservation agreement to coordinate and implement restoration and research for Pacific Lamprey. Regional plans have identified numerous threats, monitoring needs, and strategies to conserve and restore Pacific Lamprey during their freshwater life stages. Prime among these are needs to improve lamprey passage, restore freshwater habitats, educate stakeholders, and implement lamprey-specific research and management protocols. Key unknowns include range-wide trends in status, population dynamics, population delineation, limiting factors, and marine influences. We synthesize these key unknowns, with a focus on ...

Variations in marine prey availability and nutritional quality can affect juvenile salmon growth and survival during early ocean residence. Salmon growth, and hence survival, may be related to the onset of piscivory, but there is limited knowledge on the interplay between the prey field, environment, and salmon ontogeny. Subyearling Chinook Salmon (Oncorhynchus tshawytscha) and their potential prey were sampled in coastal waters off Willapa Bay, USA to explore this issue. Three seasonal prey assemblages were identified, occurring in spring (May), early summer (June – July), and late summer (August – September). The onset of piscivory, based on salmon stomach contents, fatty acids, and stable isotopes occurred later in 2011 compared to 2012, and coincided with the appearance of Northern Anchovy (Engraulis mordax). Salmon fork length (FL) and carbon isotope values (δ13C) increased with a fatty acid biomarker for marine phytoplankton and decreased with a freshwater marker, indicating dietary carbon sources changed as salmon emigrated from the Columbia River. Salmon FL also increased with nitrogen isotope ratios (δ15N), trophic position, and a fatty acid marker for piscivory – a consequence of the ontogenetic shift in diet to fish. Salmon grew faster and obtained larger size and condition by September 2011 compared to 2012, which was related to inter-annual differences in ocean conditions and the duration over which Northern Anchovy were available. Our results support the idea that juvenile salmon growth depends on the onset and duration of piscivory, suggesting both of these factors may be important components of lifetime growth and fitness.

The degree to which fine-scale habitat use by salmonid species and stocks varies within habitat types such as estuaries is not fully resolved. We sampled shallow shoreline and deeper main-stem channel habitats in the Columbia River estuary over 3 years to compare salmon species composition, migration timing, density, size, and production type (hatchery or natural). Results indicated a high degree of spatial heterogeneity in habitat occupancy by the five salmonid species that are native to the basin. Salmonid communities at two channel habitat sites were much more similar to each other than to the community at a shoreline site. Salmonids sampled at the shoreline site were primarily subyearling Chinook Salmon Oncorhynchus tshawytscha and Chum Salmon O. keta and yearling Coho Salmon O. kisutch, with few other salmonids present. In contrast, channel habitat contained a higher diversity of salmon species, with samples representing all species of anadromous salmonids, including Sockeye Salmon O. nerka a...

Juvenile salmon transitioning from freshwater to marine environments experience high variation in growth and survival, yet the specific causes of this variation are poorly understood. Size at and timing of ocean entry may contribute to this variation because they influence both the availability of prey and vulnerability to predators. To explore this issue, we used stock assignments based on genetic stock identification and internal tags to document the stock-specific size and timing of juvenile hatchery and presumed wild Columbia River Chinook Salmon Oncorhynchus tshawytscha and steelhead O. mykiss at ocean entry during 2007–2011. We found that juvenile salmon and steelhead had consistent stock-specific capture dates, with lower-river stocks typically having earlier timing than those originating farther upstream. Mean size also varied among stocks and was related to hatchery practices. Hatchery yearling Chinook Salmon and steelhead were consistently larger than wild fish from the same stocks, alth...

The underlying causes of mortality during critical life stages of fish are not well understood, nor is it clear if these causes are similar for naturally versus artificially propagated (i.e. hatchery) individuals. To assess the importance of selective mortality related to production type (hatchery vs. naturally produced) and size at and timing of marine entry, we compared attributes of juvenile Chinook salmon Oncorhynchus tshawytscha from the upper Columbia River summer- and fall-run genetic stock group captured in the Columbia River estuary with back-calculated attributes of survivors captured in marine waters. We used genetic stock identification, otolith chemistry and structure, and physical tags to determine stock of origin, size at and timing of mar- ine entry, and production type. Fish emigrated from fresh water in May to September and the majority of fish collected in the estuary (87%) had arrived within 3 d of capture. In 1 of 2 yr, timing of marine entry for both production types differed between the estuary and ocean: the ocean catch included a greater proportion of juveniles that emigrated in late July than the estuary catch. There was no evidence of selective mortality of smaller juveniles during early marine residence in hatchery or natural juveniles, but the mean percentage (±SE) of hatchery fish in ocean collections was 16 ± 5.8% less than in the estuary, which could indicate reduced survival compared to naturally produced fish. Results from this study highlight the need to understand the effects of hatchery rearing and how hatchery propagation may influence survival during later critical life-history transitions.

All anadromous fishes, including juvenile salmon, encounter estuarine habitats as they transition from riverine to marine environments. We compare the estuarine use between juvenile Atlantic salmon (Salmo salar) in the Penobscot River estuary and Pacific salmon (Oncorhynchus spp.) in the Columbia River estuary. Both estuaries have been degraded by anthropogenic activities. Atlantic and Pacific salmon populations in both basins rely heavily on hatchery inputs for persistence. Pacific salmon, as a group, represent a continuum of estuarine use, from species that move through rapidly to those that make extensive use of estuarine habitats. While Atlantic salmon estuarine use is predominantly similar to rapidly moving Pacific salmon, they can exhibit nearly the entire range of Pacific salmon estuarine use. Both slow and rapidly migrating Atlantic and Pacific salmon actively feed in estuarine environments, consuming insect and invertebrate prey. Interactions between juvenile salmon and estuarine fish communities are poorly understood in both estuaries, although they experience similar avian and marine mammal predators. Estuaries are clearly important for Atlantic and Pacific salmon, yet our understanding of this use is currently insufficient to make informed judgments about habitat quality or overall estuary health. This review of salmonid migration through and residency within estuaries identifies actions that could hasten restoration of both Atlantic and Pacific salmon populations.

Several evolutionarily significant units (ESUs) of Columbia River asin Chinook Salmon Oncorhynchus tshawytscha and Coho Salmon O. kisutch are listed as threatened or endangered under the U.S. Endangered Species Act. Yet little is known about the spatial and temporal distributions of these ESUs immediately following ocean entry, when year-class success may be determined. We documented differences in dispersal patterns during the early ocean period among groups defined by ESU, adult run timing, and smolt age. Between 1995 and 2006, 1,896 coded-wire-tagged juvenile fish from the Columbia River basin were recovered during 6,142 research trawl events along the West Coast of North America. Three distinct ocean dispersal patterns were observed: (1) age-1 (yearling) mid and upper Columbia River spring-run and Snake River spring–summer-run Chinook Salmon migrated rapidly northward and by late summer were not found south of Vancouver Island; (2) age-0 (subyearling) lower Columbia River fall, upper Columbia ...

Relative to extensive research on the freshwater stages of steelhead Oncorhynchus mykiss life history, little is known about the species’ estuarine and early marine phases despite the decline of numerous populations, including several from the Columbia River. Comparisons of the distribution, diet, and growth of juvenile steelhead collected during surveys of the Columbia River estuary and coastal waters in May, June, and September 1998–2011 were analyzed for comparisons between fish caught in the estuary and ocean and between hatchery (marked) and putative wild (unmarked) fish. Almost all catches of juvenile steelhead in the ocean occurred during the May surveys (96%). Juvenile steelhead were consistently caught at the westernmost stations (>55 km from shore), indicating an offshore distribution. Based on otolith structure and chemistry, we determined that these juveniles had been in marine waters for an average of only 9.8 d (SD = 10.2). Some of the steelhead that had been in marine waters for 1–3...

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.

Coho salmon (Oncorhynchus kisutch) populations that spawn in the coastal rivers of Oregon, U.S.A., formerly supported robust fisheries but are now listed as a “threatened species” under the U.S. Endangered Species Act. Climate change is an increasing concern in salmon conservation, and we assess the effects of climate change on sustainability of this population group. Four distinct habitats are important to different life-history stages of coho salmon: terrestrial forests, freshwater rivers and lakes, estuaries, and the ocean. Each of these habitats is affected by multiple aspects of climate change, resulting in a complex web of pathways influencing sustainability. We summarize regional climate change studies to predict future climate patterns affecting these habitats, identify the ecological pathways by which these patterns affect coho salmon, and review coho salmon ecology to assess the likely direction and magnitude of population response. Despite substantial uncertainties in specific effects ...

This study adapts and applies the evidence‐based approach for causal inference, a medical standard, to the restoration and sustainable management of large‐scale aquatic ecosystems. Despite long‐term investments in restoring aquatic ecosystems, it has proven difficult to adequately synthesize and evaluate program outcomes, and no standard method has been adopted. Complex linkages between restorative actions and ecosystem responses at a landscape scale make evaluations problematic and most programs focus on monitoring and analysis. Herein, we demonstrate a new transdisciplinary approach integrating techniques from evidence‐based medicine, critical thinking, and cumulative effects assessment. Tiered hypotheses about the effects of landscape‐scale restorative actions are identified using an ecosystem conceptual model. The systematic literature review, a health sciences standard since the 1960s, becomes just one of seven lines of evidence assessed collectively, using critical thinking strategies, causal criteria, and cumulative effects categories. As a demonstration, we analyzed data from 166 locations on the Columbia River and estuary representing 12 indicators of habitat and fish response to floodplain restoration actions intended to benefit culturally and economically important, threatened and endangered salmon. Synthesis of the lines of evidence demonstrated that hydrologic reconnection promoted macrodetritis export, prey availability, and juvenile fish access and feeding. Upon evaluation, the evidence was sufficient to infer cross‐boundary, indirect, compounding, and delayed cumulative effects, and suggestive of nonlinear, landscape‐scale, and spatial density effects. Therefore, on the basis of causal inferences regarding food‐web functions, we concluded that the restoration program is having a cumulative beneficial effect on juvenile salmon. The lines of evidence developed are transferable to other ecosystems: modeling of cumulative net ecosystem improvement, physical modeling of ecosystem controlling factors, meta‐analysis of restoration action effectiveness, analysis of data on target species, research on critical ecological uncertainties, evidence‐based review of the literature, and change analysis on the landscape setting. As with medicine, the science of ecological restoration needs scientific approaches to management decisions, particularly because the consequences affect species extinctions and the availability of ecosystem services. This evidence‐based approach will enable restoration in complex coastal, riverine, and tidal‐fluvial ecosystems like the lower Columbia River to be evaluated when data have accumulated without sufficient synthesis.

Advances in salmon culture practices during the latter part of the 20th century provided the opportunity for mass production of juvenile salmon. Hatchery-produced salmon currently outnumber wild salmon in some regions around the Pacific Rim, raising concerns about their ecological impacts on wild salmon. We convened five regional sessions at an international conference to identify and discuss issues related to ecological interactions between wild and hatchery salmon. Session participants were charged with identifying key interaction types by salmon life stage. Each group was asked to summarize key research needs and identify management actions that might be needed to reduce risks from hatchery programs. Some common themes emerged in all the sessions, including the importance of predation and competition interactions in freshwater environments during juvenile life stages and breeding interactions among adults. Much less is understood about interactions in estuarine and marine ecosystems, even though these environments may be critical in determining recruitment success. Some groups identified a need for field experiments to test hypotheses related to ecological interactions and the need to understand and, where possible, control hatchery straying. Some groups also discussed the importance of carrying capacity in different environments and how hatchery programs may be contributing to density-dependent effects. There is a lack of focused studies on ecological interactions between wild and hatchery salmon in the Western Pacific. The authors of this paper hope to encourage new research efforts to better understand ecological interactions to help inform management efforts aimed at reducing hatchery risks to wild salmon.

Ecological interactions between natural and hatchery juvenile salmon during their early marine residence, a time of high mortality, have received little attention. These interactions may negatively influence survival and hamper the ability of natural populations to recover. We examined the spatial distributions and size differences of both marked (hatchery) and unmarked (a high proportion of which are natural) juvenile Chinook salmon in the coastal waters of Oregon and Washington from May to June 1999–2009. We also explored potential trophic interactions and growth differences between unmarked and marked salmon. Overlap in spatial distribution between these groups was high, although catches of unmarked fish were low compared to those of marked hatchery salmon. Peak catches of hatchery fish occurred in May, while a prolonged migration of small unmarked salmon entered our study area toward the end of June. Hatchery salmon were consistently longer than unmarked Chinook salmon especially by June, but unmarked salmon had significantly greater body condition (based on length-weight residuals) for over half of the May sampling efforts. Both unmarked and marked fish ate similar types and amounts of prey for small (station) and large (month, year) scale comparisons, and feeding intensity and growth were not significantly different between the two groups. There were synchronous interannual fluctuations in catch, length, body condition, feeding intensity, and growth between unmarked and hatchery fish, suggesting that both groups were responding similarly to ocean conditions.

The coded wire tag (CWT) database contains detailed information on millions of Pacific salmon Oncorhynchus spp. released from hatcheries or smolt traps and recovered in the north Pacific Ocean and its tributaries. I used this data set to examine the spatial and temporal variation in the marine distributions of 77 hatchery and 16 wild populations of Chinook salmon O. tshawytscha based on recoveries of an estimated 632,000 tagged salmon in coastal waters from southern California to the Bering Sea during 1979–1994 (and 1995–2004 for select hatcheries). Chinook salmon showed 12 distinct region-specific recovery patterns. Chinook salmon originating in a common freshwater region had similar marine distributions, which were distinct from those of adjacent regions. Different run types (e.g., spring, summer, and fall runs) originating in the same region exhibited variation in their marine distributions consistent with recovery at different stages of their ocean residence period. Recovery patterns were sur...

Successfully shifting to a more piscivorous diet may be an important factor in the growth and survival of juvenile coho salmon Oncorhynchus kisutch and Chinook salmon O. tshawytscha during their first summer in the northern California Current. Nonmetric multidimensional scaling and cluster analysis of diets by size showed several distinct groupings as the salmon grew during their first marine summer. These size-based diet differences were clearly driven by increased rates of piscivory for both species. Fish prey composition, feeding intensity, and fish prey–predator length ratios all significantly increased for coho salmon at approximately 240 mm fork length when they changed from diets dominated by juvenile rockfishes Sebastes spp., the larvae of crabs Cancer spp., and adult euphausiids to one of predominantly juvenile forage fish. As Chinook salmon grew, they gradually increased the proportional contribution (by weight) of fish prey in their diets—from 55% in the smallest length-class examined ...

Little is known about the food habits of juvenile Chinook (Oncorhynchus tshawytscha) and coho (Oncorhynchus kisutch) salmon in marine environments of Alaska, or whether their diets may have contributed to extremely high marine survival rates for coho salmon from Southeast Alaska and much more modest survival rates for Southeast Alaskan Chinook salmon. To address these issues, we documented the spatial and temporal variability of diets of both species collected from marine waters of Southeast Alaska during summers of 1997–2000. Food habits were similar: major prey items of both species included fishes, crab larvae, hyperiid amphipods, insects, and euphausiids. Multivariate analyses of diet composition indicated that the most distinct groups were formed at the smallest spatial and temporal scales (the haul), although groups also formed at larger scales, such as by month or habitat type. Our expectations for how food habits would influence survival were only partially supported. As predicted, Southeast Alaskan coho salmon had more prey in their stomachs overall [1.8% of body weight (BW)] and proportionally far fewer empty stomachs (0.7%) than either Alaskan Chinook (1.4% BW, 5.1% empty) or coho salmon from other regions. However, contrary to our expectations, coho salmon diets contained surprisingly few fish (49% by weight). Apparently, Alaskan coho salmon achieved extremely high marine survival rates despite a diet consisting largely of small, less energetically-efficient crustacean prey. Our results suggest that diet quantity (how much is eaten) rather than diet quality (what is eaten) is important to marine survival.

One aspect of diadromy that has received little attention is buoyancy regulation in fish moving between freshwater and marine environments. Because of density differences between the two water types, fish must alter their whole-fish density (WFD) or they will become positively (float) or negatively (sink) buoyant as they change environments. This idea was first suggested over 80 year ago but has been largely overlooked by the scientific community. To explore how fish regulate buoyancy during this important transition, I measured WFD and lipid levels and estimated swim bladder volumes (SBVs) of juvenile coho salmon Oncorhynchus kisutch collected from freshwater and marine environments. These fish exhibited increased WFD with increasingly dense environments, suggesting active buoyancy regulation. Most of the WFD increase was attributable to decreases in SBV, although hatchery coho salmon also exhibited decreased lipid levels with increasing WFD. Hatchery coho salmon had significantly higher lipid l...

Conservation of Pacific salmon (Oncorhynchus spp.) has become increasingly important as major populations have declined in abundance to the point of being listed under the U.S. Endangered Species Act. The complex life-history of Pacific salmon species and the diversity of habitats they occupy require multifaceted recovery efforts, and the metrics needed to evaluate species status and progress toward recovery are necessarily complex. Formal decision support systems (DSS) are designed to assist decision-makers in integrating and evaluating many factors. We describe a knowledge-based DSS for evaluating the biological status of Oregon coast coho salmon (O. kisutch). We then compare our DSS to similar tools and consider its advantages and disadvantages. We show how the DSS can provide a transparent and logical framework linking multiple criteria across geographic scales for a unified assessment. Once constructed, the DSS can serve as an institutional knowledge base, codifying the pathways from data to criteria evaluation and supporting consistent future status evaluations with a path to incorporating new knowledge over time. The DSS was not trivial to implement, nor is it easy to explain to resource managers, and we offer suggestions to address these problems. The DSS was particularly helpful in providing a logical and reproducible way to quantify multiple risks and assess progress toward recovery across multiple spatial and temporal scales. Development of this DSS is an important step in the evolution of assessment tools for salmon conservation.

Information developed during recently completed evaluations of the status of seven species of anadromous Pacific salmonids (Oncorhynchus spp.) in the Pacific Northwest was used to characterize patterns of intraspecific diversity along three major axes: ecology, life history and biochemical genetics. Within the study area, the species' ranges, and therefore the number of distinct ecological regions inhabited differ considerably, with pink and chum salmon limited to the northern areas and chinook salmon and steelhead distributed over the widest geographic range. The species showed comparable differences in the patterns of life history and genetic diversity, with chinook and sockeye salmon and steelhead having the most major diversity groups and pink, chum and coho salmon having the least. Both life history and genetic diversity showed a strong, positive correlation with the extent of ecological diversity experienced by a species, and the correlation between the number of major genetic and life history groups within a species was even stronger (r=0.96; P

The listing of 13 salmon and steelhead stocks in the Columbia River basin (hereafter collectively referred to as “salmon”) under the Endangered Species Act of 1973, as amended, has stimulated tidal wetland restoration in the lower 235 kilometers of the Columbia River and estuary for juvenile salmon habitat functions. The purpose of the research reported herein was to evaluate the effect on listed salmon of the restoration effort currently being conducted under the auspices of the federal Columbia Estuary Ecosystem Restoration Program (CEERP). Linking changes in the quality and landscape pattern of tidal wetlands in the lower Columbia River and estuary (LCRE) to salmon recovery is a complex problem because of the characteristics of the ecosystem, the salmon, the restoration actions, and available sampling technologies. Therefore, we designed an evidence-based approach to develop, synthesize, and evaluate information to determine early-stage (~10 years) outcomes of the CEERP. We developed an ecosystem conceptual model and from that, a primary hypothesis that habitat restoration activities in the LCRE have a cumulative beneficial effect on juvenile salmon. There are two necessary conditions of the hypothesis: • habitat-based indicators of ecosystem controlling factors, processes, and structures show positive effects from restoration actions, and • fish-basedmore » indicators of ecosystem processes and functions show positive effects from restoration actions and habitats undergoing restoration. Our evidence-based approach to evaluate the primary hypothesis incorporated seven lines of evidence, most of which are drawn from the LCRE. The lines of evidence are spatial and temporal synergies, cumulative net ecosystem improvement, estuary-wide meta-analysis, offsite benefits to juvenile salmon, landscape condition evaluation, and evidence-based scoring of global literature. The general methods we used to develop information for the lines of evidence included field measurements, data analyses, modeling, meta-analysis, and reanalysis of previously collected data sets. We identified a set of 12 ancillary hypotheses regarding habitat and salmon response. Each ancillary hypothesis states that the response metric will trend toward conditions at relatively undisturbed reference sites. We synthesized the evidence for and against the two necessary conditions by using eleven causal criteria: strength, consistency, specificity, temporality, biological gradient, plausibility, coherence, experiment, analogy, complete exposure pathway, and predictive performance. Our final evaluation included cumulative effects assessment because restoration is occurring at multiple sites and the collective effect is important to salmon recovery. We concluded that all five lines of evidence from the LCRE indicated positive habitat-based and fish-based responses to the restoration performed under the CEERP, although tide gate replacements on small sloughs were an exception. Our analyses suggested that hydrologic reconnections restore access for fish to move into a site to find prey produced there. Reconnections also restore the potential for the flux of prey from the site to the main stem river, where our data show that they are consumed by salmon. We infer that LCRE ecosystem restoration supports increased juvenile salmon growth and enhanced fitness (condition), thereby potentially improving survival rates during the early ocean stage.« less

In August 1992, we conducted an intensive short-term (within 119 d) experiment in southern Willapa Bay, Washington, to evaluate the potential effects on mudflat benthic communities of herbicide control of smooth cordgrass, Spartina alterniflora Loisel. A mixture of glyphosate (Rodeo® ; 4.7 L ha -1 ) and an associated surfactant, alkylarylpolyoxyethylene (AAPOE, X-77® Spreader ; 1 L ha -1 ) was applied aerially to three mudflat sites with invasive S. alterniflora. Sediment structure (grain size), edaphic microalgal biomass (chlorophyll a), and densities of benthic and epibenthic meiofauna and benthic macrofauna were sampled systematically in treated and adjacent control (untreated) plots I d before, immediately after, and 1, 14, 28 and 119 d after spraying. These mudflat biota showed no definitive differences in population trends that would indicate acute responses to the herbicide and surfactant applications over the 119-d duration of the experiment. Two-way ANOVA tests of differences in slope of linear regressions of mean plot microalgal biomass and invertebrate density of 19 taxa groups or species testing short-term (2 weeks) and long-term (17 weeks) trends in response to the experimental treatment tests indicated no significant (p < 0.1) treatment and only three site effects. Natural variability in the standing stocks (in the case of benthic microalgae) or densities (invertebrates) of most of the 19 indicator taxa prior to spray application was sufficiently high within and between treatment and control plots and among sites to preclude strong inferential tests of acute effects. Although differences in mudflat habitats (e.g., tidal elevation, sediment structure) inherent in the sites prior to treatment affect the power of our ability to test direct effects, there were no indications of either short- or long-term effects on the mudflat community of aerially applying this concentration of herbicide and surfactant. This study did not explicitly address either sublethal or indirect ecological effects, such as associated with an observed decrease in the exotic eelgrass Zostera japonica, which might appear as a longer-term, more subtle response by the mudflat community.

Gray whales (Eschrichtius robustus) residing in Puget Sound, Washington, U.S.A., in 1990 and 1991 created feeding pits on littoral sand flats dominated by ghost shrimp (Callianassa californiensis). The whales removed an extensive biomass of shrimp from the pits. Ghost shrimp standing stock was 2–5 times lower inside than outside feeding pits, equivalent to a removal of 3–6 kg of shrimp per pit. An estimated 2700–3200 feeding pits were present on 19 km of sand flat in 1990, while 19 000 feeding pits were documented over the same region in spring and summer, 1991. We estimated that 10–12 and 75 t of shrimp were removed from the pits in 1990 and 1991, respectively. Ghost shrimp represent an energetically valuable prey for gray whales, providing 2–15 times higher standing stocks than any other reported prey. We discuss our results in the context of conflicts with human activity, impacts on the littoral community, and the significance of an expanding gray whale population.

Widespread population extirpations and the consequent loss of ecological, genetic, and life-history diversity can lead to extinction of evolutionarily significant units (ESUs) and species. We attempted to systematically enumerate extinct Pacific salmon populations and characterize lost ecological, life history, and genetic diversity types among six species of Pacific salmon (Chinook [Oncorhynchus tshawytscha], sockeye [O. nerka], coho [O. kisutch], chum [O. keta], and pink salmon [O. gorbuscha] and steelhead trout [O. mykiss]) from the western contiguous United States. We estimated that, collectively, 29% of nearly 1400 historical populations of these six species have been lost from the Pacific Northwest and California since Euro-American contact. Across all species there was a highly significant difference in the proportion of population extinctions between coastal (0.14 extinct) and interior (0.55 extinct) regions. Sockeye salmon (which typically rely on lacustrine habitats for rearing) and stream-maturing Chinook salmon (which stay in freshwater for many months prior to spawning) had significantly higher proportional population losses than other species and maturation types. Aggregate losses of major ecological, life-history, and genetic biodiversity components across all species were estimated at 33%, 15%, and 27%, respectively. Collectively, we believe these population extirpations represent a loss of between 16% and 30% of all historical ESUs in the study area. On the other hand, over two-thirds of historical Pacific salmon populations in this area persist, and considerable diversity remains at all scales. Because over one-third of the remaining populations belong to threatened or endangered species listed under the U.S. Endangered Species Act, it is apparent that a critical juncture has been reached in efforts to preserve what remains of Pacific salmon diversity. It is also evident that persistence of existing, and evolution of future, diversity will depend on the ability of Pacific salmon to adapt to anthropogenically altered habitats.