Fall and Winter Movement Dynamics of Naturally Produced Spring Chinook Salmon Parr in Two Neighboring Interior Pacific Northwest Natal Rivers

Abnormal growths were observed on the lips and in the oral cavities of 2- and 3-year-old Chinook salmon (Oncorhynchus tshawytscha) maintained in one freshwater and one saltwater captive fish-rearing facility in the Columbia River (Pacific Northwest). Initially presenting as bilaterally symmetrical, red, irregular plaques on oral mucosal surfaces, the lesions developed progressively into large, disfiguring masses. Of the 502 natural parr collected for captive broodstock, 432 (86%) displayed these tumors, whereas cohort salmon (i.e., same year classes) in these same facilities remained unaffected. Morphologically similar neoplasms were collected occasionally from adult Chinook salmon that had returned to their natal streams. Histologic features of the tumors suggested that they were derived from the portion of dental lamina destined to form tooth root sulci; therefore, these neoplasms were diagnosed as ameloblastomas. The lesions also resembled archived specimens of Chinook salmon oral tumors, which had been described decades earlier. Etiologic investigations performed during the current outbreak included bacteriologic, virologic, genetic, ultrastructural analyses, and cohabitation exposure studies. Results of these efforts did not indicate an obvious genetic basis for this syndrome, attempts to isolate potentially causative viruses or bacteria were negative, and disease transmission to naïve fish was unsuccessful. A few intracytoplasmic hexagonal structures, possibly consistent with viral particles (∼100 nm), were observed ultrastructurally in a tumor cell from 1 of 6 specimens submitted for transmission electron microscopy. Although the presence of these particles does not constitute sufficient evidence for causality, an infectious or multifactorial etiology seems plausible.

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Survival of a threatened salmon is linked to spatial variability in river conditions

10.1101/2021.08.24.456882 ◽

2021 ◽

Author(s):

Colby L. Hause ◽

Gabriel P. Singer ◽

Rebecca A. Buchanan ◽

Dennis E. Cocherell ◽

Nann A. Fangue ◽

...

Keyword(s):

Pacific Northwest ◽

Chinook Salmon ◽

Habitat Restoration ◽

Oncorhynchus Tshawytscha ◽

Central Valley ◽

Data Generation ◽

Habitat Variability ◽

River Habitat ◽

San Joaquin River ◽

The Pacific

AbstractExtirpation of the Central Valley spring-run Chinook Salmon ESU (Oncorhynchus tshawytscha) from the San Joaquin River is emblematic of salmonid declines across the Pacific Northwest. Habitat restoration and fish reintroduction efforts are ongoing, but recent telemetry studies have revealed low outmigration survival of juveniles to the ocean. Previous investigations have focused on modeling survival relative to river discharge and geographic regions, but have largely overlooked the effects of habitat variability. To evaluate the link between environmental conditions and survival of juvenile spring-run Chinook Salmon, we combined high spatial resolution habitat mapping approaches with acoustic telemetry along a 150 km section of the San Joaquin River during the spring of 2019. While overall outmigration survival was low (5%), our habitat-based classification scheme described variation in survival of acoustic-tagged smolts better than other candidate models based on geography or distance. There were two regional mortality sinks evident along the longitudinal profile of the river, revealing poor survival in areas that shared warmer temperatures but that diverged in chlorophyll-α, fDOM, turbidity and dissolved oxygen levels. These findings demonstrate the value of integrating river habitat classification frameworks to improve our understanding of survival dynamics of imperiled fish populations. Importantly, our data generation and modeling methods can be applied to a wide variety of fish species that transit heterogeneous and diverse habitat types.

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Spatially overlapping salmon species have varied population response to early life history mortality from increased peak flows

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2021-0038 ◽

2021 ◽

pp. 1-10

Author(s):

Colin L. Nicol ◽

Jeffrey C. Jorgensen ◽

Caleb B. Fogel ◽

Britta Timpane-Padgham ◽

Timothy J. Beechie

Keyword(s):

Climate Change ◽

Life History ◽

Pacific Northwest ◽

Chinook Salmon ◽

Oncorhynchus Tshawytscha ◽

Early Life History ◽

Climate Change Scenarios ◽

Peak Flows ◽

Multi Stage ◽

The Pacific

In the Pacific Northwest, USA, climate change is expected to result in a shift in average hydrologic conditions and increase variability. The relative vulnerabilities to peak flow changes among salmonid species within the same basin have not been widely evaluated. We assessed the impacts of predicted increases in peak flows on four salmonid populations in the Chehalis River basin. Coupling observations of peak flows, emissions projections, and multi-stage Beverton–Holt matrix-type life cycle models, we ran 100-year simulations of spawner abundance under baseline, mid-century, and late-century climate change scenarios. Coho (Oncorhynchus kisutch) and spring Chinook salmon (Oncorhynchus tshawytscha) shared the highest projected increase in interannual variability (SD = ±15%). Spring Chinook salmon had the greatest reduction in median spawner abundance (–13% to –15%), followed by coho and fall Chinook salmon (–7% to –9%), then steelhead (Oncorhynchus mykiss) (–4%). Our results show that interspecies and life history variability within a single basin is important to consider. Species with diverse age structures are partially buffered from population variability, which may increase population resilience to climate change.

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Making progress on bycatch avoidance in the ocean salmon fishery using a transdisciplinary approach

ICES Journal of Marine Science ◽

10.1093/icesjms/fsw061 ◽

2016 ◽

Vol 73 (9) ◽

pp. 2380-2394 ◽

Cited By ~ 2

Author(s):

Saskia A. Otto ◽

Sarah Simons ◽

Joshua S. Stoll ◽

Peter Lawson

Keyword(s):

Pacific Northwest ◽

Chinook Salmon ◽

Oncorhynchus Tshawytscha ◽

Fishing Effort ◽

Fine Scale ◽

Transdisciplinary Approach ◽

Stakeholder Collaboration ◽

Study Region ◽

Fish Stocks ◽

Spatio Temporal

Abstract Transdisciplinary research that crosses disciplinary boundaries and includes stakeholder collaboration is increasingly being used to address pressing and complex socio-ecological challenges in the Anthropocene. In fisheries, we see transdisciplinary approaches being employed to address a range of challenges, including bycatch where fine-scale data are collected by fishers to help advance spatial approaches in which fishing effort is shifted away from bycatch hotspots. However, the spatio-temporal overlap of morphologically undistinguishable fish stocks, some of which are depleted, is a major concern for some fisheries, including the Pacific Northwest troll Chinook salmon (Oncorhynchus tshawytscha) fishery. In this study, we develop and evaluate a transdisciplinary approach to avoid bycatch in the commercial Chinook salmon troll fishery off northern and central Oregon. Based on a unique genetic dataset collected by fishers, fine-scale patterns of stock distribution and spatial stock overlap were assessed. Two hotspots of weak Klamath stock in the study region were identified and related to bathymetry. Results were then fed into a simple bioeconomic model to evaluate costs and benefits of reallocating effort under two scenarios of allowable catch of a weak stock (Klamath). The scenarios demonstrate that effort reallocation could lead to a reduction in Klamath catch as well as to increases in net profit, but outcomes depend on the distance from the fleets' home port to the new fishing area. The output of the model at its current stage should be regarded strategically, providing a qualitative understanding of the types of best fleet strategies. Despite some challenges in transdisciplinarity discussed in this study and the present limitations to incorporate fine-scale changes of Chinook salmon stock distributions in management regulations, we contend that this approach to research has the potential to lead to improved management outcomes.

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