Pacific Salmonids Research Articles

Relationship between effective population size, inbreeding and adult fitness‐related traits in a steelhead (Oncorhynchus mykiss) population released in the wild

Inbreeding is of concern in supportive breeding programmes in Pacific salmonids, Oncorhynchus spp, where the number of breeding adults is limited by rearing space or poor survival to adulthood, and large numbers are released to supplement wild stocks and fisheries. We reconstructed the pedigree of 6602 migratory hatchery steelhead (Oncorhynchus mykiss) over four generations, to determine the incidence and fitness consequences of inbreeding in a northwest USA programme. The hatchery maintained an effective population size, Ñ(e) = 107.9 from F(0) to F(2), despite an increasing census size (N), which resulted in a decreasing N(e)/N ratio (0.35 in F(0) to 0.08 in F(2)). The reduced ratio was attributed to a small broodstock size, nonrandom transfers and high variance in reproductive success (particularly in males). We observed accumulation of inbreeding from the founder generation (in F(4), percentage individuals with inbreeding coefficients Δf > 0 = 15.7%). Generalized linear mixed models showed that body length and weight decreased significantly with increasing Δf, and inbred fish returned later to spawn in a model that included father identity. However, there was no significant correlation between Δf and age at return, female fecundity or gonad weight. Similarly, there was no relationship between Δf and reproductive success of F(2) and F(3) individuals, which might be explained by the fact that reproductive success is partially controlled by hatchery mating protocols. This study is one of the first to show that small changes in inbreeding coefficient can affect some fitness-related traits in a monitored population propagated and released to the wild.

Use of Radiotelemetry and Direct Observations to Evaluate Sea Lion Predation on Adult Pacific Salmonids at Bonneville Dam

AbstractManagement of protected species becomes increasingly complex when one protected population negatively affects another. This occurs along coastlines and in rivers and estuaries of the U.S. Pacific Northwest, where protected marine mammals prey on threatened and endangered Pacific salmonids Oncorhynchus spp. Over 9 years, we observed a growing aggregation of California sea lions Zalophus californianus and Steller sea lions Eumetopias jubatus preying upon adult Chinook salmon O. tshawytscha and steelhead O. mykiss at Bonneville Dam on the Columbia River. Both before and concurrent with the observation study, we monitored radio‐tagged salmon at Bonneville Dam and during their upriver spawning migrations. Springtime sea lion abundance steadily increased from 2002 to 2010 and the aggregation formed earlier each winter. The principal prey species in winter were resident white sturgeon Acipenser transmontanus and migratory steelhead and then shifted to predominantly Chinook salmon when the spring run arrived. Observation‐based estimates of salmonid consumption from January to May varied 12‐fold among years (0.4–4.9%, mean = 2.6% of adult salmonids counted at the dam), and radiotelemetry results corroborated these estimates. The highest proportional impact was in winter and early spring. As salmonid abundance increased, per capita consumption by sea lions increased (Type II functional response) but individual salmonid risk decreased (due to prey swamping). Population‐specific risk analyses indicated predation was substantially higher for early‐timed than for late‐timed salmon populations. The most at‐risk group included Snake River and upper Columbia River Chinook salmon listed as threatened under the U.S. Endangered Species Act. These predation indices should help managers simultaneously tasked with salmon recovery and marine mammal management.

Using ancient DNA identification and osteometric measures of archaeological Pacific salmon vertebrae for reconstructing salmon fisheries and site seasonality at Dionisio Point, British Columbia

Determining the diversity of salmon species represented in archaeological contexts is critical to understanding patterns of salmon harvesting and consumption, storage practices and seasonal patterns of resource exploitation by precontact peoples of the Northwest Coast. We present species determinations generated for salmon vertebrae from the Dionisio Point site (DgRv-003) in coastal southwestern British Columbia, a well-preserved village site that dates to between 1500 and 1300 cal BP. Molecular species identification was possible for 70 Pacific salmonid vertebral elements recovered from one excavated plankhouse at the site. Coupled with osteometric measures, we determine that residents of the plankhouse fished primarily for chum, sockeye and pink salmon, with a lesser emphasis on chinook, coho and steelhead. These results indicate a diverse fishery that likely occurred between July and December, suggesting a mid summer through winter season of occupation for the village.

Low‐level copper exposures increase visibility and vulnerability of juvenile coho salmon to cutthroat trout predators

Copper contamination in surface waters is common in watersheds with mining activities or agricultural, industrial, commercial, and residential human land uses. This widespread pollutant is neurotoxic to the chemosensory systems of fish and other aquatic species. Among Pacific salmonids (Oncorhynchus spp.), copper-induced olfactory impairment has previously been shown to disrupt behaviors reliant on a functioning sense of smell. For juvenile coho salmon (O. kisutch), this includes predator avoidance behaviors triggered by a chemical alarm cue (conspecific skin extract). However, the survival consequences of this sublethal neurobehavioral toxicity have not been explored. In the present study juvenile coho were exposed to low levels of dissolved copper (5-20 microg/L for 3 h) and then presented with cues signaling the proximity of a predator. Unexposed coho showed a sharp reduction in swimming activity in response to both conspecific skin extract and the upstream presence of a cutthroat trout predator (O. clarki clarki) previously fed juvenile coho. This alarm response was absent in prey fish that were exposed to copper. Moreover, cutthroat trout were more effective predators on copper-exposed coho during predation trials, as measured by attack latency, survival time, and capture success rate. The shift in predator-prey dynamics was similar when predators and prey were co-exposed to copper. Overall, we show that copper-exposed coho are unresponsive to their chemosensory environment, unprepared to evade nearby predators, and significantly less likely to survive an attack sequence. Our findings contribute to a growing understanding of how common environmental contaminants alter the chemical ecology of aquatic communities.

Acquisition of polychlorinated biphenyls (PCBs) by pacific chinook salmon: An exploration of various exposure scenarios

In 2011, as part of an update to its state water quality standards (WQS) for protection of human health, the State of Oregon adopted a fish consumption rate of 175 g/day for freshwater and estuarine finfish and shellfish, including anadromous species. WQS for the protection of human health whose derivation is based in part on anadromous fish, create the expectation that implementation of these WQS will lead to lower contaminant levels in returning adult fish. Whether this expectation can be met is likely a function of where and when such fish are exposed. Various exposure scenarios have been advanced to explain acquisition of bioaccumulative contaminants by Pacific salmonids. This study examined 16 different scenarios with bioenergetics and toxicokinetic models to identify those where WQS might be effective in reducing polychlorinated biphenyls (PCBs)--a representative bioaccumulative contaminant--in returning adult Fall chinook salmon, a representative salmonid. Model estimates of tissue concentrations and body burdens in juveniles and adults were corroborated with observations reported in the literature. Model results suggest that WQS may effect limited (< approximately 2 ×) reductions in PCB levels in adults who were resident in a confined marine water body or who transited a highly contaminated estuary as out-migrating juveniles. In all other scenarios examined, WQS would have little effect on PCB levels in returning adults. Although the results of any modeling study must be interpreted with caution and are not necessarily applicable to all salmonid species, they do suggest that the ability of WQS to meet the expectation of reducing contaminant loadings in anadromous species is limited.

Chronic low pH exposure affects the seawater readiness of juvenile Pacific sockeye salmon

Chronic exposure to water of low pH during the freshwater life stage of Pacific salmonids is presently the cause for concern due to its potential to reduce subsequent performance in the marine environment. Sockeye fry (0+) were raised under sublethal long-term, low pH conditions (pH 4.8-6.8) in soft water and assessed for effects on freshwater growth, stress physiology, and seawater tolerance following smoltification. Fish gained significantly lower mass (average 46% of control [pH 6.8] values) and had lower condition factor and liver somatic index values than control fish following a 126-days exposure to water at pH 5.0. Liver glycogen concentrations (49% of control values) and whole-body lipid content (65% of control values) were also significantly lower. Low pH exposure also resulted in a sustained organismal stress response that included significant and substantial increases in plasma cortisol concentrations. Fish exposed to pH 5.0 in freshwater for 30 days exhibited an average of 14% mortality in a seawater challenge, as well as a significant osmoregulatory stress measured by increases in plasma Na⁺ and Cl⁻ concentrations as well as osmolality compared to controls. Significantly lower critical swimming speed values (U(crit)) were also seen (22% reductions compared to controls). The data generated indicate that sockeye salmon are sensitive and do not acclimate to low pH under long-term exposure conditions, potentially decreasing the probability of survival in the marine environment.

Evolution and biogeography of an emerging quasispecies: Diversity patterns of the fish Viral Hemorrhagic Septicemia virus (VHSv)

Viral Hemorrhagic Septicemia virus (VHSv) is an RNA rhabdovirus that causes one of the most important finfish diseases, affecting over 70 marine and freshwater species. It was discovered in European cultured fish in 1938 and since has been described across the Northern Hemisphere. Four strains and several substrains have been hypothesized, whose phylogenetic relationships and evolutionary radiation are evaluated here in light of a quasispecies model, including an in-depth analysis of the novel and especially virulent new substrain (IVb) that first appeared in the North American Laurentian Great Lakes in 2003. We analyze the evolutionary patterns, genetic diversity, and biogeography of VHSv using all available RNA sequences from the glycoprotein (G), nucleoprotein (N), and non-virion (Nv) genes, with Maximum Likelihood and Bayesian approaches. Results indicate that the G gene evolves at an estimated rate of μ=2.58×10−4 nucleotide substitutions per site per year, the N gene at μ=4.26×10−4, and Nv fastest at μ=1.25×10−3. Phylogenetic trees from the three genes largely are congruent, distinguishing strains I–IV as reciprocally monophyletic with high bootstrap and posterior probability support. VHSv appears to have originated from a marine ancestor in the North Atlantic Ocean, diverging into two primary clades: strain IV in North America (the Northwestern Atlantic Ocean), and strains I–III in the Northeastern Atlantic region (Europe). Strain II may comprise the basal group of the latter clade and diverged in Baltic Sea estuarine waters; strains I and III appear to be sister groups (according to the G and Nv genes), with the former mostly in European freshwaters and the latter in North Sea marine/estuarine waters. Strain IV is differentiated into three monophyletic substrains, with IVa infecting Northeastern Pacific salmonids and many marine fishes (with 44 unique G gene haplotypes), IVb endemic to the freshwater Great Lakes (11 haplotypes), and a newly-designated IVc in marine/estuarine North Atlantic waters (five haplotypes). Two separate substrains independently appeared in the Northwestern Pacific region (Asia) in 1996, with Ib originating from the west and IVa from the east. Our results depict an evolutionary history of relatively rapid population diversifications in star-like patterns, following a quasispecies model. This study provides a baseline for future tracking of VHSv spread and interpreting its evolutionary diversification pathways.

Development and Evaluation of a Data Dictionary to Standardize Salmonid Habitat Assessments in the Pacific Northwest

ABSTRACTRestoration ecology and conservation biology have increasingly recognized the need for a common language to facilitate the combining of data sets to help identify threats, degraded habitat, and appropriate restoration response. However, to date no tool exists that can standardize language for large quantities of publicly available information relevant to the analysis and management of threatened and endangered Pacific salmonids. Here, I present a simple and transparent method for integrating assessments of degraded salmonid habitat into a database using a data dictionary. The data dictionary is then used to measure similarity between independently created assessments for subbasins within the Columbia‐Cascade region. The relationship between the number of restoration projects and the number of assessed ecological concerns is also compared. This initial investigation illustrates the data dictionary's utility in defining a set of salmonid‐specific ecological concerns, providing a means to integrate habitat assessments to encompass a wider area and measure the concordance between different assessments conducted over the same geographical area. The ability to standardize and integrate information on degraded habitat provides an important link in a logical chain connecting habitat conditions to the restoration projects intended to enhance populations of threatened and endangered salmonids.

Conserving imperiled species: a comparison of the IUCN Red List and U.S. Endangered Species Act

AbstractThe United States conserves imperiled species with the Endangered Species Act (ESA). No studies have evaluated the ESA's coverage of species on the International Union for Conservation of Nature (IUCN) Red List, which is an accepted standard for imperiled species classification. We assessed the ESA's coverage of IUCN‐listed birds, mammals, amphibians, gastropods, crustaceans, and insects, and studied the listing histories of three bird species and Pacific salmonids in more detail. We found that 40.3% of IUCN‐listed U.S. birds are not listed by the ESA, and most other groups are underrecognized by &gt;80%. Species with higher IUCN threat levels are more frequently recognized by the ESA. Our avian case studies highlight differences in the objectives, constraints, and listing protocols of the two institutions, and the salmonids example shows an alternative situation where agencies were effective in evaluating and listing multiple (related) species. Vague definitions ofendangeredandthreatened, an inadequate ESA budget, and the existence of thewarranted but precludedcategory likely contribute to the classification gap we observed.

Spatial–temporal scales of synchrony in marine zooplankton biomass and abundance patterns: A world-wide comparison

Large scale synchrony in the fluctuations of abundance or biomass of marine fish populations in regions on opposite sides of an ocean basin or in different oceans have been viewed as externally forced by correlated environmental stochasticity (e.g., common external forcing), most often as atmospheric teleconnections of basin-to-global scale atmospheric forcing, such as the Arctic Oscillation, North Atlantic Oscillation or the Pacific Decadal Oscillation. Specific causal mechanisms have been difficult to unequivocally discover, but possible mechanisms include influences on habitat temperatures, productivity operating through bottom-up (trophodynamic) mechanisms or direct climate influence on the fish populations (top-down mechanisms). For small pelagic fishes (sardines and anchovies) in widely separated large marine ecosystems that lack obvious ocean interconnectivity, it has been argued that the teleconnections may be atmospheric, acting on the fishes directly and propagating to the ecosystem from the middle out (wasp-waist species). Zooplankton biomass or abundance time series data from >100 sites world-wide are used to examine the spatial scales of coherent temporal synchrony. If spatially correlated environmental factors (like climate) are important for creating synchrony in fish populations via bottom-up effects (trophic interactions involving fish prey, e.g., zooplankton), then we would expect to observe synchrony in fluctuations of zooplankton biomass/numbers at spatial scales similar to those found for fish species. Zooplankton biomass/abundance have 50% spatial decorrelation scales of ca. 700–1400km and scales of significant coherence that extend to separation distances of ca. 3000km. These are also the spatial scales of environmental (sea surface temperature) synchrony from our global analysis. These scales are slightly greater than the 50% decorrelation scales of ca. 150–700km for recruitment synchrony in Atlantic marine fish and survival and recruitment synchrony of Northeast Pacific salmonids (150–1000km depending on species). However, the spatial scales of synchrony of annual zooplankton biomass anomalies in the Humboldt Current, California Current and Kuroshio ecosystems of the Pacific are much too small (ca. 2000km) to be directly causal of the basin-scale (7000–15,000km) synchrony exhibited by sardine and/or anchovy populations in those ecosystems.

A riverscape perspective of Pacific salmonids and aquatic habitats prior to large‐scale dam removal in the Elwha River, Washington, USA

Abstract Dam removal has been increasingly proposed as a river restoration technique. In 2011, two large hydroelectric dams will be removed from Washington State’s Elwha River. Ten anadromous fish populations are expected to recolonise historical habitats after dam removal. A key to understanding watershed recolonisation is the collection of spatially continuous information on fish and aquatic habitats. A riverscape approach with an emphasis on biological data has rarely been applied in mid‐sized, wilderness rivers, particularly in consecutive years prior to dam removal. Concurrent snorkel and habitat surveys were conducted from the headwaters to the mouth (rkm 65–0) of the Elwha River in 2007 and 2008. This riverscape approach characterised the spatial extent, assemblage structure and patterns of relative density of Pacific salmonids. The presence of dams influenced the longitudinal patterns of fish assemblages, and species richness was the highest downstream of the dams, where anadromous salmonids still have access. The percent composition of salmonids was similar in both years for rainbow trout, Oncorhynchus mykiss (Walbaum), coastal cutthroat trout, Oncorhynchus clarkii clarkii (Richardson) (89%; 88%), Chinook salmon, Oncorhynchus tshawytscha (Walbaum) (8%; 9%), and bull trout, Salvelinus confluentus (Suckley) (3% in both years). Spatial patterns of abundance for rainbow and cutthroat trout (r = 0.76) and bull trout (r = 0.70) were also consistent between years. Multivariate and univariate methods detected differences in habitat structure along the river profile caused by natural and anthropogenic factors. The riverscape view highlighted species‐specific biological hotspots and revealed that 60–69% of federally threatened bull trout occurred near or below the dams. Spatially continuous surveys will be vital in evaluating the effectiveness of upcoming dam removal projects at restoring anadromous salmonids.

Exceptional aerobic scope and cardiovascular performance of pink salmon (Oncorhynchus gorbuscha) may underlie resilience in a warming climate

Little is known of the physiological mechanisms underlying the effects of climate change on animals, yet it is clear that some species appear more resilient than others. As pink salmon (Oncorhynchus gorbuscha) in British Columbia, Canada, have flourished in the current era of climate warming in contrast to other Pacific salmonids in the same watershed, this study investigated whether the continuing success of pink salmon may be linked with exceptional cardiorespiratory adaptations and thermal tolerance of adult fish during their spawning migration. Sex-specific differences existed in minimum and maximum oxygen consumption rates (M(O2,min) and M(O2,max), respectively) across the temperature range of 8 to 28°C, reflected in a higher aerobic scope (M(O2,max)-M(O2,min)) for males. Nevertheless, the aerobic scope of both sexes was optimal at 21°C (T(opt)) and was elevated across the entire temperature range in comparison with other Pacific salmonids. As T(opt) for aerobic scope of this pink salmon population is higher than in other Pacific salmonids, and historic river temperature data reveal that this population rarely encounters temperatures exceeding T(opt), these findings offer a physiological explanation for the continuing success of this species throughout the current climate-warming period. Despite this, declining cardiac output was evident above 17°C, and maximum attainable swimming speed was impaired above ∼23°C, suggesting negative implications under prolonged thermal exposure. While forecasted summer river temperatures over the next century are likely to negatively impact all Pacific salmonids, we suggest that the cardiorespiratory capacity of pink salmon may confer a selective advantage over other species.

Mechanisms influencing competition between hatchery and wild juvenile anadromous Pacific salmonids in fresh water and their relative competitive abilities

Avoiding negative effects of competition from released hatchery salmonids on wild fish is a primary concern for recovery efforts and fisheries management. Several factors affect competition among juvenile salmonids including: (1) whether competition is intra- or interspecific, (2) duration of freshwater cohabitation of hatchery and wild fish, (3) relative body size, (4) prior residence, (5) environmentally induced developmental differences, and (6) fish density. Intraspecific competition is expected to be greater than interspecific because of greater niche overlap between conspecific hatchery and wild fish. Competition is expected to increase with prolonged freshwater cohabitation. Hatchery smolts are often larger than wild, and larger fish are usually superior competitors. However, wild fish have the advantage of prior residence when defending territories and resources in natural streams. Hatchery-induced developmental differences are variable and can favor both hatchery and wild fish. Although all these factors influence competitive interactions, fish density of the composite population (wild + hatchery fish) in relation to habitat carrying capacity likely exerts the greatest influence. The extent of competition and relative competitive ability of wild and hatchery fish can be determined by additive and substitutive experimental designs, respectively, and the limited body of substitutive experiments suggests that the relative competitive ability of hatchery and wild fish is approximately equal when measured as growth. Conducting substitutive experiments becomes difficult as the spatial and temporal scales increase. Large-scale experiments comparing supplemented and control reaches or streams hold some promise for quantifying the effects of released hatchery fish on wild fish behavior, growth and survival.

Detections of Eleven Organophosphorus Insecticides and One Herbicide Threatening Pacific Salmonids, Oncorhynchus spp., in California, 1991–2010

California's surface water monitoring results from 1991 through 2010 were analyzed to determine whether 12 organophosphorus insecticides and herbicides (i.e., azinphos methyl, bensulide, dimethoate, disulfoton, ethoprop, fenamiphos, methamidophos, methidathion, methyl parathion, naled, phorate, and phosmet) and their degradates have been detected above maximum concentration limits (MCLs) in Pacific salmonid habitats. Methidathion, methyl parathion, phorate, phosmet, and the oxygen analogue of naled (DDVP) detections exceeded MCLs. Methyl parathion detections may be accounted for by monthly use trends, while methidathion detections may be explained by yearly use trends. There were inadequate phorate, phosmet, or DDVP data to evaluate for correlations with use.

Nearshore ecosystem predictors of a bacterial infection in juvenile Chinook salmon

Disease epidemiology requires information about ecological and environmental condi- tions to identify factors that can influence disease progression. Bacterial kidney disease (BKD) is an endemic disease among Pacific Northwest salmonids that causes significant morbidity and mortality in artificially propagated stocks, but risk factors for infection among free-living salmon are unknown. We evaluated infection by the causative agent of BKD, Renibacterium salmoninarum, in 1752 fish across 52 sampling sites monthly from May to November 2003 as a component of a broader study of neritic habitat use in Puget Sound by juvenile Chinook salmon Oncorhynchus tshawytscha. Infection intensity was ≤10 cells per slide for 77% of the fish. Correlations between the density of Chinook salmon with infection prevalence and with infection intensity were observed across multiple spatial scales. Capture location was a stronger predictor of infection than fish origin (based on coded wire tags) or genetic stock. Influential risk factors by logistic regression were temperature, densities of marked and unmarked Chinook salmon, and density of river lamprey Lampetra ayresis. Renibac- terium salmoninarum were found in gut contents and kidney of river lamprey, suggesting this species may be a transmission vector. The low infection intensity, lack of an effect of fish origin, effect of capture bay, and strong associations with Chinook salmon density are consistent with horizontal transmission of R. salmoninarum during the juvenile neritic phase, posing a potential for infectious interaction between sympatric hatchery and wild fish.

Physiological Characterization of Hatchery-Origin Juvenile SteelheadOncorhynchus mykissAdopting Divergent Life-History Strategies

AbstractSmoltification by juvenile Pacific salmonids has been described as a developmental conflict whereby individuals face several life-history decisions. Smoltification occurs as a result of interactions between organismal condition and environmental cues, although some fish may forgo ocean migration and remain in freshwater streams for some time (residualize). We compared the physiological profiles of steelhead that were actively migrating to the ocean (migratory fish) and those that remained in fresh water (residuals) for at least a period of between 2 wk and 3 mo after release from a hatchery facility. In addition, we investigated the physiological characterization of residuals that further differentiated into precocial freshwater residents or parr that will either precocially mature in fresh water or migrate to the ocean in the future. Residuals had higher condition factors and gonadosomatic index than migratory fish and were characterized as less prepared for saltwater due to low levels of gill Na+,K+-ATPase activity and Na+,K+-ATPase α1b-subunit expression. Residuals tended to be males with the highest condition factors. Sex-specific differences are probably reflective of male fish adopting an alternative life-history strategy foregoing outmigration as a result of condition at the time of release. Collection of residuals throughout the fall suggested that residual hatchery fish further diversify into precocially mature fish that will presumably attempt to spawn without ever migrating to the ocean or into parr that will precocially mature or migrate in a future year.

Does Lower Crab Creek in the Eastern Washington Desert Have a Native Population of Chinook Salmon?

AbstractLower Crab Creek (LCC) in eastern Washington is a groundwater‐fed tributary to the Columbia River at river kilometer 661. The creek traverses agriculturally modified desert habitat, and in several reaches the water quality is poor, summer water temperatures are lethal to fish, and stream habitat is degraded. The creek was thought to be unsuitable for salmonids, yet fall‐run Chinook salmon Oncorhynchus tshawytscha spawn and rear in it. The origin of these fish is uncertain since it is unclear whether LCC was a perennial creek prior to the hydrologic changes in the Columbia River basin stemming from the Columbia Basin Irrigation Project in the 1950s. We used genetic analyses to examine the hypotheses that these fish are (1) random strays, (2) a population founded since the 1950s (by wild or hatchery strays), or (3) an established native population. Chinook salmon juveniles and adults were collected in LCC and genetically characterized with the Chinook salmon microsatellite DNA locus suite in the Genetic Analysis of Pacific Salmonids database. The LCC population of Chinook salmon was found to be significantly different from interior Columbia River basin hatchery and wild populations and to have alleles that are absent from proximal populations. Lower Crab Creek Chinook salmon showed no evidence of recent founding and had genetic diversity, allelic richness, and effective population size similar to those of other Columbia River basin Chinook salmon. The data suggest that a genetically distinct, native population of Chinook salmon inhabits LCC that has adapted to the rigorous environment.

Potential effects of global climate change on National Fish Hatchery operations in the Pacific Northwest, USA

Global climate change is predicted to be a major force in altering ecosystem processes and animal behavior worldwide in the coming years. Currently, many Pacific salmon Oncorhynchus spp. stocks are imperiled due to harvest, habitat loss, and anthropogenic disturbance across much of their native range, and climate change has been predicted to have further negative effects on these species. Artificial propagation has been used by multiple resource agencies to conserve salmon pop- ulations and increase numbers in the Columbia River watershed, including the National Fish Hatch- ery (NFH) system in the Pacific Northwest, which annually produces more than 60 million juvenile Pacific salmonids. The species and populations that are supplemented through the NFH system, as well as operations at the NFHs themselves, will be affected by global climate change and forced to adapt. This review provides a preliminary summary of the potential effects of climate change on the NFH system in the Pacific Northwest, focusing on the topics that will be of most relevance to NFH operations. A series of proactive measures, which are in various stages of action, are outlined that should quantify climate change threats to the operations of specific NFHs and allow for flexibility in adjusting operations to continue to meet conservation and supplementation goals in the face of an uncertain future.

Effects of Healing Time and Pulsed‐DC Waveform on Injury Detection and Incidence in Electroshocked Juvenile Chinook Salmon

AbstractElectrofishing is widely used to assess juvenile Pacific salmonids in freshwaters, but electroshock‐induced injury may result. The small size of juvenile fish makes detection of internal injuries, particularly spinal injuries, more difficult than in adult fish. To test the idea that growth and healing of vertebral injuries over time would render injuries more detectable, we exposed age‐1 Chinook salmon Oncorhynchus tshawytscha to conventional 60‐Hz pulsed direct current (PDC) and dual‐frequency PDC (DFPDC; 568 and 15 Hz) in a tank study. To simulate field conditions, capture‐prone behaviors (immobilization and forced swimming) were achieved by applying 60‐Hz PDC at a voltage gradient of 1.1 V/cm and DFPDC at 5.0 V/cm. Because electroshock treatments occurred only on day 0, we assumed that all injuries occurred on that day. Evaluation of injuries on days 1, 7, 14, 28, and 56 of a 56‐d experiment revealed decreasingly detectable hemorrhages (as a result of healing) but increasingly detectable spinal injuries. Incidences of spinal injury induced by 60‐Hz PDC and 568‐Hz and 15‐Hz DFPDC were both high (40–80% range) and not significantly different. However, fish responses to electroshock (behavior, bruising, mortality, and growth) followed a trend of greater severity for PDC than for DFPDC. Fewer age‐0 fish were available; on day 0, they were exposed only to PDC and evaluated only on days 1 and 56. The most marked increase in detection of spinal injuries was observed in age‐0 fish: the injury rate increased from 0% on day 1 to 53% on day 56. Immobilization of Chinook salmon (and presumably other juvenile salmonids) by 60‐Hz PDC will cause significant trauma. Use of dual‐frequency PDC, even at the higher voltage levels sufficient to immobilize these fish, will reduce these effects. Estimates of spinal injury rates in electroshocked juvenile salmonids may be biased downward unless sufficient time has passed for healing and growth to occur, thereby increasing the probability of radiographic detection.

The effect of a supplementation program on the genetic and life history characteristics of an Oncorhynchus mykiss population

Conservation hatcheries, which supplement natural populations by removing adults or embryos from the natural environment and rearing and releasing parr, smolts, or adults back into their natal or ancestral streams, are increasingly being used to avoid extinction of localized populations of Pacific salmonids. We collected data before and during a steelhead ( Oncorhynchus mykiss ) supplementation program to investigate the effect that the program has had on the population’s genetic diversity and effective population size and any changes to an important life history trait (residency or anadromy). We found that supplementation did not cause substantial changes in the genetic diversity or effective size of the population, most likely because a large proportion of all of the steelhead redds in the river each year were sampled to create the supplementation broodstock. Our data also showed that the captively reared fish released as adults successfully produced parr. Furthermore, we found that during supplementation, there was an increase in the proportion of O. mykiss with anadromous ancestry vs. resident ancestry.