19 research outputs found
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Buoyancy regulation by hatchery and wild coho salmon during the transition from freshwater to marine environments
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 levels than wild coho salmon in both freshwater and marine environments. These high lipid levels may impede the ability of hatchery fish to regulate buoyancy and may increase their vulnerability to surface predators. Furthermore, lipid levels that vary with both environmental water density and fish origin clearly complicate the interpretation of this variable during the important transition from freshwater to the ocean.Keywords: Oncorhynchus kisutch, lipids, buoyanc
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Seasonal and interannual variation in juvenile salmonids and associated fish assemblage in open waters of the lower Columbia River estuary
The transition between freshwater and marine environments is associated with high mortality for juvenile anadromous salmonids, yet little is known about this critical period in many large rivers. To address this deficiency, we investigated the estuarine ecology of juvenile salmonids and their associated fish assemblage in open-water habitats of the lower Columbia River estuary during spring of 2007–10. For coho (Oncorhynchus kisutch), sockeye (O. nerka), chum (O. keta), and yearling (age 1.0) Chinook (O. tshawytscha) salmon, and steelhead (O. mykiss), we observed a consistent seasonal pattern characterized by extremely low abundances in mid-April, maximum abundances in May, and near absence by late June. Subyearling (age 0.0) Chinook salmon were most abundant in late June. Although we observed interannual variation in the presence, abundance, and size of juvenile salmonids, no single year was exceptional across all species-and-age classes. We estimated that >90% of juvenile Chinook and coho salmon and steelhead were of hatchery origin, a rate higher than previously reported. In contrast to juvenile salmonids, the abundance and composition of the greater estuarine fish assemblage, of which juvenile salmon were minor members, were extremely variable and likely responding to dynamic physical conditions in the estuary. Comparisons with studies conducted 3 decades earlier suggest striking changes in the estuarine fish assemblage—changes that have unknown but potentially important consequences for juvenile salmon in the Columbia River estuary.This is the publisher’s final pdf. The published article is copyrighted by National Marine Fisheries Service, NOAA, Scientific Publications Office and can be found at: http://fishbull.noaa.gov
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Juvenile Steelhead Distribution, Migration, Feeding, and Growth in the Columbia River Estuary, Plume, and Coastal Waters
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 d were captured at the westernmost edge of survey transects, indicating rapid offshore migration. Estuary-caught fish ate fewer prey types and consumed far less food than did ocean-caught fish, which ate a variety of prey, including juvenile fishes, euphausiids, and crab megalopae. Estuary- and ocean-caught unmarked fish exhibited higher feeding intensities, fewer empty stomachs, and better condition than hatchery fish. Growth hormone levels (insulin-like growth factor 1 [IGF-1]) in unmarked fish and hatchery fish varied annually, with unmarked fish having slightly higher overall values. In general, the FL, condition, stomach fullness, and IGF-1 of ocean-caught steelhead increased with distance offshore. Unlike juveniles of other salmonid species, steelhead appeared to quickly migrate westward from coastal rivers and showed patterns of increased feeding and growth in offshore waters. An understanding of the estuarine and ocean ecology of steelhead smolts may assist in the management of threatened steelhead populations
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Spatial and trophic overlap of marked and unmarked Columbia River Basin spring Chinook salmon during early marine residence with implications for competition between hatchery and naturally produced fish
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 andWashington
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.Keywords: Wild, Competition, Spatial, Marine, Hatchery, Columbia River Basin, Juvenile Chinook salmon, Trophi
Climate vulnerability assessment for Pacific salmon and steelhead in the California Current Large Marine Ecosystem.
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
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Marine distributions of chinook salmon from the West Coast of North America determined by coded wire tag recoveries
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 surprisingly stable across years, despite high interannual variation in ocean conditions. By contrast, ocean age influenced recovery patterns, as older fish were recovered further from their natal stream than younger fish. Although most of the CWT data used in the analysis came from hatchery fish, recoveries of tagged wild populations indicate patterns similar to those of fish from nearby hatcheries. The consistency in these findings across broad geographic areas suggests that they apply to Chinook salmon across the entire Pacific Rim. Similar findings for tagged coho salmon O. kisutch indicate that the observed patterns may apply to Pacific salmon as a whole and provide a model for other highly migratory fishes that have not benefited from such intensive tagging programs. The results also have implications for the genetic control of migration and salmon’s ability to respond to climate change.Keywords: Oncorhynchus tshawytscha, tagging, hatcherie
Pacific Salmon Extinctions: Quantifying Lost and Remaining Diversity
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
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Evidence for selective mortality in marine environments: the role of fish migration size, timing, and production type
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 marine
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.Keywords: Size‑selective mortality, Early marine survival, Hatchery, Naturally propagated, Otolith, Chinook salmonKeywords: Size‑selective mortality, Early marine survival, Hatchery, Naturally propagated, Otolith, Chinook salmo
An Evidence-Based Evaluation of the Cumulative Effects of Tidal Freshwater and Estuarine Ecosystem Restoration on Endangered Juvenile Salmon in the Columbia River: Final Report
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-based 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