Prevalence of Infection in Hatchery‐Origin Chinook Salmon Correlates with Abundance of <i>Ceratonova shasta</i> Spores: Implications for Management and Disease Risk

Robinson, H. Eve; Alexander, Julie D.; Hallett, Sascha L.; Som, Nicholas A.

doi:10.1002/nafm.10456

Cited by 9 publications

(16 citation statements)

References 36 publications

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“…In addition, in the NE Pacific, salmon enhancement hatcheries subsidize natural salmon populations, and since 1950, 3.7 billion Chinook salmon have been released into the Salish Sea from hatcheries in the United States and British Columbia (BC) ( 43 ). The risk posed from emerging infectious disease associated with hatchery fish varies ( 13 , 44 , 45 ) and is largely unknown with respect to PRV-1.…”

Section: Introductionmentioning

confidence: 99%

Aquaculture mediates global transmission of a viral pathogen to wild salmon

et al. 2021

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Global expansion of aquaculture and agriculture facilitates disease emergence and catalyzes transmission to sympatric wildlife populations. The health of wild salmon stocks critically concerns Indigenous peoples, commercial and recreational fishers, and the general public. Despite potential impact of viral pathogens such as Piscine orthoreovirus-1 (PRV-1) on endangered wild salmon populations, their epidemiology in wild fish populations remains obscure, as does the role of aquaculture in global and local spread. Our phylogeographic analyses of PRV-1 suggest that development of Atlantic salmon aquaculture facilitated spread from Europe to the North and South East Pacific. Phylogenetic analysis and reverse transcription polymerase chain reaction surveillance further illuminate the circumstances of emergence of PRV-1 in the North East Pacific and provide strong evidence for Atlantic salmon aquaculture as a source of infection in wild Pacific salmon. PRV-1 is now an important infectious agent in critically endangered wild Pacific salmon populations, fueled by aquacultural transmission.

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Section: Introductionmentioning

confidence: 99%

Aquaculture mediates global transmission of a viral pathogen to wild salmon

et al. 2021

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“…Study area.-The study area was comprised of three sites on the Klamath River below Iron Gate Dam, the upstream barrier for anadromous salmonids in the Klamath River, in a portion of the river commonly referred to as the C. shasta "infectious zone" (Hallett and Bartholomew 2006;Robinson et al 2020). These sites were selected because they contain habitat conditions representative of the infectious zone, including areas ranging from never inhabiting annelids to those known to consistently host annelids.…”

Section: Methodsmentioning

confidence: 99%

Reducing River Flows to Control a Parasitic Salmonid Disease in the Klamath River: Simulations Question the Efficacy of Desiccation as a Management Tool

Turecek

Payton

Alexander

et al. 2021

N American J Fish Manag

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Aquatic parasites cause disease in economically and culturally important Klamath River salmonids Oncorhynchus spp., and the myxozoan parasite Ceratonova shasta has been linked to high juvenile salmonid mortality. Because C. shasta requires the freshwater annelid Manayunkia occidentalis to complete its life cycle, management approaches have focused on disrupting annelid populations to reduce C. shasta and disease risk for salmonids. Previous studies have demonstrated that manipulating river discharge to achieve short‐term, high‐flow events is effective for disturbing annelids. There is also interest in the efficacy of manipulating river discharge to desiccate annelids to reduce disease risk. To investigate the efficacy of reducing streamflow to desiccate annelids, we simulated the amount of annelid habitat, categorized by quality, that would be dewatered as discharge was incrementally reduced. Simulations were accomplished by coupling two‐dimensional hydrodynamic models with an annelid presence/absence model. Simulations were conducted for three study sites located on the Klamath River main stem downstream of Iron Gate Dam, where discharge can be manipulated. Reductions in discharge from June base flow (31.2 m3/s or 1,100 ft3/s) to the lowest simulated discharge rate (17.0 m3/s; approximately half of base flow) resulted in an 11.8% reduction of the total wetted area of the river across all three study sites combined. For the same discharge simulation, reductions in annelid habitat differed based on the quality of habitat, with low‐ quality (<0.20 probability of annelids) to moderate‐quality (0.20–0.80 probability of annelids) habitat reduced by 8.3% (95% credible interval = 7.5–10.3) and 23.7% (10.7–27.5), respectively, while high‐quality habitat (>0.80 probability of annelids) was never desiccated. These results suggest that desiccation is unlikely to offer an effective solution for managing myxozoan parasites of salmonids that are transmitted by annelids because reducing streamflow had minimal effects on the amount of annelid habitat.

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“…Further, an epidemiological model describing how C. shasta dynamics respond to future climate scenarios found that high winter discharge had the greatest impact on lowering the number of infected juvenile fish ( Ray et al, 2015 ), and a statistical model for annelid habitat suitability related hydraulic and substrate variables to annelid host distribution in the Klamath River ( Alexander et al, 2016 ). Other analyses have found a correlative relationship between the prevalence of infection of hatchery-released smolts and the spring peak of spore densities the following year ( Robinson et al, 2020 ), suggesting seasonal links contributing to spore density. This suite of mechanistic and statistical models provides the groundwork to inform simulations of C. shasta during the outmigration period.…”

Section: Introductionmentioning

confidence: 95%

“…In addition, approximately five million Chinook Salmon smolts are released from Iron Gate Hatchery (located below Iron Gate Dam, Fig. 1 ) each year between mid-May and early-June, a period that frequently coincides with peak C. shasta densities ( Robinson et al, 2020 ), exposing hatchery-origin fish to potentially high mortality.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, the prevalence of infection in adult salmon is high and not variable, as returning adult fish are immunosuppressed and vulnerable to infection ( Dolan et al, 2016 ); yet a small percentage of carcasses are the highest contributors of myxospores ( Foott et al, 2016 ). As the Schakau, Hilker & Lewis (2019) model predicts infection in adult salmonids, and there is no detectable relationship that links returning spawners with the abundance of spring actinospores ( Robinson et al, 2020 ), a different model design is required to simulate the density of spores in spring that contributes to disease risk in outmigrating juvenile salmonids.…”

Section: Introductionmentioning

confidence: 99%

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Using a mechanistic framework to model the density of an aquatic parasiteCeratonova shasta

Robinson

Alexander

Bartholomew

et al. 2022

PeerJ

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Ceratonova shasta is a myxozoan parasite endemic to the Pacific Northwest of North America that is linked to low survival rates of juvenile salmonids in some watersheds such as the Klamath River basin. The density of C. shasta actinospores in the water column is typically highest in the spring (March–June), and directly influences infection rates for outmigrating juvenile salmonids. Current management approaches require quantities of C. shasta density to assess disease risk and estimate survival of juvenile salmonids. Therefore, we developed a model to simulate the density of waterborne C. shasta actinospores using a mechanistic framework based on abiotic drivers and informed by empirical data. The model quantified factors that describe the key features of parasite abundance during the period of juvenile salmon outmigration, including the week of initial detection (onset), seasonal pattern of spore density, and peak density of C. shasta. Spore onset was simulated by a bio-physical degree-day model using the timing of adult salmon spawning and accumulation of thermal units for parasite development. Normalized spore density was simulated by a quadratic regression model based on a parabolic thermal response with river water temperature. Peak spore density was simulated based on retained explanatory variables in a generalized linear model that included the prevalence of infection in hatchery-origin Chinook juveniles the previous year and the occurrence of flushing flows (≥171 m3/s). The final model performed well, closely matched the initial detections (onset) of spores, and explained inter-annual variations for most water years. Our C. shasta model has direct applications as a management tool to assess the impact of proposed flow regimes on the parasite, and it can be used for projecting the effects of alternative water management scenarios on disease-induced mortality of juvenile salmonids such as with an altered water temperature regime or with dam removal.

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Prevalence of Infection in Hatchery‐Origin Chinook Salmon Correlates with Abundance of Ceratonova shasta Spores: Implications for Management and Disease Risk

Cited by 9 publications

References 36 publications

Aquaculture mediates global transmission of a viral pathogen to wild salmon

Aquaculture mediates global transmission of a viral pathogen to wild salmon

Reducing River Flows to Control a Parasitic Salmonid Disease in the Klamath River: Simulations Question the Efficacy of Desiccation as a Management Tool

Using a mechanistic framework to model the density of an aquatic parasiteCeratonova shasta

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