Salmonid distribution and abundance in the context of Elwha River dam removals

Removal of two dams on the Elwha River, Washington from 2011 to 2014 has begun to restore natural sediment processes to the coastal environment near the river mouth. Since 2006, we have been collecting data on shallow subtidal (nearshore) fish communities near the Elwha River and at reference sites in the Strait of Juan de Fuca to assess fish response to sediment changes resulting from dam removal. Juvenile salmon (Chinook, coho, pink and chum salmon) migrate through this region, which also supports ecologically important forage fish and endemic benthic fauna. Beach seine samples collected annually from April through September from over 20 sites span pre-removal, high impact (during dam removal), and post-removal years. Annual catches included 23,093 to 92,677 individuals from 45-55 species. Trends in species richness and abundance were variable over this time period. Forage fish dominated our catches followed by salmonids. In this analysis we explored patterns of juvenile salmonid abundance in relation to dam removal, environmental variables, site characteristics (including community composition), and year/season using a Bayesian hierarchical modeling framework and multivariate analyses. Chinook salmon show a tenfold variation in abundance over the years examined. Catches of Chinook and coho salmon were dominated by locally released hatchery fish with high variability between sampling sites. Throughout this region we have seen a marked decrease in coho salmon catches in recent years. Understanding what biotic and abiotic factors contribute most to this variability in salmon abundance and distribution may help tailor future dam removal processes or reframe management decisions

Spatio-temporal variation in the nearshore forage fish community in the Strait of Juan de Fuca

Nearshore marine habitats in the Salish Sea support populations of many fish species including migrating juvenile salmon, benthic sculpins, and rearing and spawning forage fish. The Strait of Juan de Fuca (SJF) is critical as a corridor between the Pacific Ocean and inland water bodies. Though known to utilize this area, the population dynamics of ecologically important forage fish are poorly understood. Over 9 years of monthly beach seine sampling (April – September) at 24 sites along 70 km of coastline in the SJF, we have observed high variability in fish catch across years, sites, and seasons. Annual catches ranged from 23,093 to 92,677 individual fish divided among 45 to 55 species. Forage fish were represented by 9 species and were numerically the dominant group, accounting for 87.8% of the catch from all sampling areas combined. Three forage fish species dominated, thus warranting in-depth investigation: Pacific Herring (Clupea pallasii), Pacific Sand Lance (Ammodytes hexapterus), and Surf Smelt (Hypomesus pretiosus). Influence of individual species varied, yet drove the fish assemblage structure. We explored effects of temporal and spatial variability on forage fish occurrence, abundance, and community composition using descriptive statistics and a Bayesian hierarchical modeling framework. Additionally, the removal of two large dams on the adjacent Elwha River, which released stored sediment into our sampling area, provided us an opportunity to examine forage fish response to a localized habitat perturbation. Spatially, individual species may avoid regions of high perturbation but dramatic variations in distribution and abundance of the greater forage fish community are temporally driven by larger scale changes. Management plans directed at forage fish should take into consideration how variation in abundance at regional scales and consistent population responses to large-scale environmental fluctuations may drive forage fish populations over time

Comparison of triploid and diploid rainbow trout (Oncorhynchus mykiss) fine-scale movement, migration and catchability in lowland lakes of western Washington

Fisheries managers stock triploid (i.e., infertile, artifcially produced) rainbow trout Oncorhynchus mykiss in North American lakes to support sport fsheries while minimizing the risk of genetic introgression between hatchery and wild trout. In Washington State, the Washington Department of Fish and Wildlife (WDFW) allocates approximately US $3 million annually to stock hatchery-origin rainbow trout in>600 lakes, yet only about 10% of them are triploids. Many lakes in Washington State drain into waters that support wild anadromous steelhead O. mykiss that are listed as threatened under the U.S. Endangered Species Act. As a result, there is a strong interest in understanding the costs and benefts associated with stocking sterile, triploid rainbow trout as an alternative to traditional diploids. The objectives of this study were to compare triploid and diploid rainbow trout in terms of: (1) contribution to the sport fshery catch, (2) fne-scale movements within the study lakes, (3) rate of emigration from the lake, and (4) natural mortality. Our results demonstrated that triploid and diploid trout had similar day-night distribution patterns, but triploid trout exhibited a lower emigration rate from the lake and lower catch rates in some lakes. Overall, triploid rainbow trout represent a viable alternative to stocking of diploids, especially in lakes draining to rivers, because they are sterile, have comparable home ranges, and less often migrat

Cumulative Effects of Natural and Anthropogenic Stress on Immune Function and Disease Resistance in Juvenile Chinook Salmon

Previous studies have shown that juvenile chinook salmon Oncorhynchus tshawytscha exposed in the field or the laboratory to polychlorinated biphenyls (PCBs), an anthropogenic stressor, are immunosuppressed. It is not known whether simultaneous exposure to natural stressors can increase this immunosuppression. To examine the effects of natural and anthropogenic stressors on immune function, we infected juvenile chinook salmon with metacercariae of the trematode Nanophyetus salmincola by exposing the fish to infected freshwater snails Juga plicifera. Infected (>300 metacercariae per fish) and noninfected salmon were then injected with either the commercial PCB mixture Aroclor 1254 or an acetone-emulphor carrier. B cell function was examined by in vitro hemolytic plaque-forming cell (PFC) assay. Nanophyetus salmincola infection resulted in significantly lower anterior kidney primary PFCs and lower splenic secondary PFCs. The combination of N. salmincola infection and Aroclor 1254 exposure caused a lower anterior kidney primary PFC response than did either stressor alone. The immune function of juvenile chinook salmon was also measured by challenging them with the marine bacterium Listonella anguillarum (formerly known as Vibrio anguillarum). Fish infected with N. salmincola had higher mortalities than noninfected fish when challenged with L. anguillarum. These experiments demonstrated that N. salmincola infection in juvenile chinook salmon can impair immune function and disease resistance. The findings also show that in combination these natural and anthropogenic stressors can have a greater negative effect on salmon health than either stressor alone.Keywords: stress, Oncorhynchus tshawytscha, polychlorinated biphenyls, immunosuppressio

Movements of sub-adult Chinook salmon, Oncorhynchus tshawytscha, in Puget Sound, Washington, as indicated by ultrasonic tracking

Salmonids show a wide variety of migration patterns. Such variation is especially prevalent in Chinook salmon, Oncorhynchus tshawytscha. This species migrates to coastal and open ocean waters, and the tendency to use these different marine environments varies markedly among populations. For example, some Chinook salmon that enter Puget Sound do not migrate to the sea as juveniles in their first year but rather remain as “residents” through (at least) the following Spring. Known locally as blackmouth, these fish are the focus of extensive sport fisheries. In this study, we used acoustic telemetry to examine questions surrounding resident Chinook salmon in Puget Sound. The overall objective of this study was to determine the extent to resident and migratory behavior patterns are distinct or ends of a continuum of movement patterns, and then characterize the movements of resident fish. We first assessed the proportion of fish, caught and tagged as immature residents (inferred from the locations and dates of capture), that remained within Puget Sound and the proportion that moved to the coastal region, and tested the hypotheses that origin (wild or hatchery), location and season of tagging, fish size and condition factor would influence the tendency to remain resident. Second, we characterized the movements by resident fish with Puget Sound at a series of different spatial scales: movement among the major basins, travel rates, and areas of concentration within Puget Sound. Third, we tested the model of seasonal north-south movement patterns by examining the distribution of detections over the whole area and year. Because residents represent a significant portion of the Puget Sound Chinook salmon Evolutionarily Significant Unit, currently listed as Threatened under the U. S. Endangered Species Act, better understanding of their movements in Puget Sound will help identify critical habitat use patterns and evaluate fishery management objectives as the species crosses jurisdictional boundaries

Lessons learned from community and citizen science monitoring on the Elwha River restoration project

Community and citizen science (CCS) projects – initiatives that involve public participation in scientific research – can both sustain and expand long-term monitoring of large dam removal projects. In this article, we discuss our perspectives on CCS associated with the Elwha River dam removals. We summarize how the public has been or could be involved in monitoring and distill lessons learned for other large dam removal projects. Much of the Elwha monitoring involved technical field work requiring training and incurring potential liability risks, guiding projects towards smaller-scale public involvement. Partnering with organizations that have capacity for volunteer management expanded CCS opportunities and provided logistical support to project managers committed to public engagement. We found that many projects engaged with students and/or with paid or unpaid interns; compensating participants in various ways can help to create reciprocal relationships that support long-term monitoring. In the future, other large dam removals could consider planning ahead for community involvement in dam removal monitoring to accommodate the technical and potentially hazardous nature of the work – broadening who may be able to participate. In addition, involving community members in setting research agendas could be an important first step in engaging them in long-term monitoring, in turn facilitating multi-generational research at the timescale of landscape-level changes. Finally, explicit relationship-building with Indigenous communities can enhance the benefits of community engagement in dam removal science for all involved

Increased Susceptibility of Juvenile Chinook Salmon to Vibriosis after Exposure to Chlorinated and Aromatic Compounds Found in Contaminated Urban Estuaries

Saltwater-adapted juvenile chinook salmon Oncorhynchus tshawytscha exposed to aromatic and chlorinated compounds, representative of contaminants found in urban estuaries in Puget Sound, have a higher susceptibility to vibriosis than do fish exposed only to the solvent vehicle. Susceptibility to vibriosis was assessed by examining the percent cumulative mortality of the salmon after exposure to the bacterial pathogen Vibrio anguillarum. The aromatic and chlorinated compounds examined consisted of a sediment extract from the Hylebos Waterway that was enriched in butadienelike compounds (chlorinated-enriched Hylebos Waterway sediment extract [CHWSE]), a model mixture of polycyclic aromatic hydrocarbons (PAHs), a polychlorinated biphenyl mixture (Aroclor 1254), hexachlorobutadiene (HCBD), and 7,12-dimethylbenz[a]anthracene (DMBA). Two trials were conducted. In trial l, the percent cumulative mortality of juvenile chinook salmon exposed to V. anguillarum after receiving either CHWSE, HCBD, or the model mixture of PAHs ranged from 28% to 31% compared with the 16% observed in the acetone:emulphor control group at 7 d post-bacterial challenge. In trial 2, the net cumulative mortality of juvenile chinook salmon exposed to V. anguillarum after receiving either DMBA or Aroclor 1254 ranged from 46% to 49% compared with the 25% observed in the acetone:emulphor control group at 9 d postchallenge. The differences in mortality between groups of fish in the treated and control groups in both trials were significant at P 0.05. These findings suggest that a higher predisposition to infection and subsequent disease can occur in salmon exposed to chemical contaminants found in urban estuaries of Puget Sound, WashingtonKeywords: polychlorinated-biphenyls, juveniles, Vibriosis, Oncorhynchus tshawytscha, estuarie

Survey of Pathogens in Juvenile Salmon Oncorhynchus Spp. Migrating through Pacific Northwest Estuaries

Although the adverse impact of pathogens on salmon populations in the Pacific Northwest is often discussed and recognized, little is currently known regarding the incidence and corresponding significance of delayed disease-induced mortalities. In the study reported herein, we surveyed the presence and prevalence of selected micro- and macroparasites in out-migrant juvenile coho salmon Oncorhynchus kisutch and Chinook salmon O. tshawytscha from 12 coastal estuaries in the Pacific Northwest over a 6-year period (1996-2001). The major finding of this study was the widespread occurrence of pathogens in wild salmon from Pacific Northwest estuaries. The six most prevalent pathogens infecting both juvenile Chinook and coho salmon were Renibacterium salmoninarum, Nanophyetus salmincola, an erythrocytic cytoplasmic virus (erythrocytic inclusion body syndrome or erythrocytic necrosis virus), and three gram-negative bacteria (Listonella anguillarum, Yersinia ruckeri, and Aeromonas salmonicida). The most prevalent pathogen in both Chinook and coho salmon was N. salmincola, followed by the pathogens R. salmoninarum and the erythrocytic cytoplasmic virus. Statistically significant differences in the prevalence of R.. salmoninarum and N. salmincola were observed between Chinook and coho salmon. Based on the prevalence of pathogens observed in this study, disease appears to be a potentially significant factor governing the population numbers of salmon in the Pacific Northwest. Development of a detailed understanding of the principal components influencing the ecology of infectious disease will aid in the development of management and control strategies to mitigate disease in and hence further the recovery of salmon stocks listed under the Endangered Species Act

Evaluating Responses of Nearshore Fish to Removal of the Elwha River Dams

Removal of two dams on the Elwha River began in late 2011 and will restore sediment processes in the near coastal environment adjacent to the river\u27s mouth. Since 2005, we have been collecting data on intertidal/sub-tidal fish communities near the mouth of the River where we expect sediment changes to occur. We have also sampled in reference areas. Samples were collected by beach seining in the spring and summer. Our primary objective has been to determine if attributes of the nearshore fish community (notably species assemblage structure and size distribution) changed in response to sediment restoration. Potential shifts in fish assemblage structure and size distribution of ecologically important species such as forage fish and juvenile salmon are of particular interest because sediment changes will likely be significant in these intertidal and sub-tidal habitats. Trends in species richness and abundance were consistent prior to and following dam removal (2012 is thus far the only year where we have post dam removal information) with reference areas generally possessing more species and a greater overall abundance of fish than treatment areas. Forage fish were the numerically dominate species group in all areas. Using multivariate analysis, we found considerable overlap in fish community composition between years but there was some separation in fish assemblage structure between the different areas prior to dam removal. Regional differences were primarily a result of several forage fish species (notably Pacific sandlance, and surf smelt) and juvenile salmonid species (notably chum salmon). There were also seasonal differences in all regions with salmonids and forage fish the dominate fish in the spring and flatfish, sculpins, perch, and greenlings the primary species occurring in summer. Inclusion of post-dam removal data from 2012 did not significantly change these observed patterns. We plan to continue monitoring in the future. However, our ability to detect responses of fish communities to sediment changes will ultimately depend on both biotic factors (such as species and life stages being considered) and abiotic factors, such as when sediment reaches the coastal environment; the quantity, composition and distribution of the material that reaches the Salish Sea; and how long it takes material to distribute from the river’s mouth

Movements of sub-adult Chinook salmon (Oncorhynchus tshawytscha) in Puget Sound, Washington, as indicated by hydroacoustic tracking

Alternative forms of migratory behavior can have substantial consequences for the growth, survival, and fitness of the individuals involved. Salmonids vary in the tendency of individuals to migrate to marine waters (anadromy) or remain in freshwater habitats. In addition, substantial variation in migratory patterns can exist among anadromous and resident species. This talk summarizes our use of hydroacoustic telemetry to investigate the movement patterns of anadromous Chinook salmon Oncorhynchus tshawytscha remaining in the marine waters of Puget Sound after ocean entry rather than continuing out to the coastal waters of the North Pacific Ocean, as is typical of the species. We then compared the movement patterns of Chinook salmon with those of a closely related species, coho salmon O. kisutch. Most (37 of 53 = 70%) Chinook salmon remained in Puget Sound (“residents”) and few of those left the region within Puget Sound where they were first captured, despite ready access to suitable habitat elsewhere. However, 30% of the individuals, termed transients, subsequently left Puget Sound and moved to the coastal Pacific Ocean. Residents and transients did not differ in initial body size, date or place of tagging, or rearing history (hatchery or wild). Combined with other sources of information, these data support the conclusion that Chinook and coho salmon display alternative forms of migratory behavior (resident and transient) that are best described as modes along a continuum rather than discrete categories. However, in both species the residents showed very limited movement within Puget Sound; this behavior affects their exposure to agents of natural mortality, fisheries, and other physiological processes such as the uptake of chemical contaminants