We propose a workshop to review the current approaches to assessing and modelling salmon survival across freshwater/coastal and marine life history stages and to recommend options that will inform the host of management tools/processes that require consideration of the full life history. We will bring together experts possessing experience with these techniques to share their knowledge in a structured manner. Case studies drawn from Pacific Salmon Treaty stocks that have requisite information will be developed that can be used to test the modelling approach. A Workshop Technical Planning Team will be convened from North Pacific Anadromous Fish Commission -International Year of the Salmon partner government agencies, NGO’s and academia to ensure relevance of the work to management and to assist in identifying a complete complement of experts. Experts will include representatives from Pacific Salmon Commission Secretariat staff and Technical Committees (Chinook, Coho, Chum and Sockeye). We will support travel for experts from Asia, Canada, Europe and the U.S. to attend. It will be essential for us to incorporate approaches to understanding freshwater and marine ecosystem status with Indigenous Peoples. Additionally, we will assess the potential for the development of new and emerging technologies and citizen science to augment this work.
Age data derived from scale, whole otolith, and otolith thermal mark analyses are critical to sustainable fisheries management and the assessment of salmon fisheries and to evaluate recovery efforts for imperilled salmon populations. However, to our knowledge, a formal comparison of age estimates derived from these methods has not been completed for Chum and Sockeye salmon. The objective of this proposal is to provide corroboration of age estimates that are paramount to the run-reconstruction, in-season fishery management, and forecasts of these stocks. We propose to compare paired age estimates derived from scale (Chum) and whole otolith (Sockeye) analysis and otolith thermal mark analysis (Chum and Sockeye) for greater than 12,500 adult Chum and Sockeye salmon over the last two decades in Washington State. This analysis will identify the level of precision between estimates and any bias between methods and directly addresses Southern panel priority of improving salmon escapement assessments.
Since 2015, the Washington Department of Fish and Wildlife (WDFW) has been working to improve Chum escapement estimates resulting in two technical reports (Edwards and Zimmerman 2018; Ronne et al. 2019). Previous work assessed distribution inside versus outside index reaches, area-under-the-curve estimates within index reaches, carcass tagging estimates of abundance in select index reaches, estimates of spawner stream life duration, and total spawner abundance of Chum salmon within tributaries of Grays Harbor. This proposal seeks to further implement an accurate and precise method for estimating escapement of Chum in sub-basins yet to be evaluated. Utilizing new methods, we also seek to revise run size estimates of historical abundance. This methodology can be used in other systems throughout the area covered by the Pacific Salmon Treaty. Current escapement estimates in Puget Sound and coastal Washington are derived from methods developed in the 1970s with the understanding that those methods were based on unsubstantiated assumptions that would later be revisited and refined. Over 40 years later, those methods are still being used for escapement estimates. Chum have become a constraining stock on the Grays Harbor salmon fisheries. Therefore, refined Chum assessments may alter management strategies moving forward.
The proposed work will address Southern Panel Priority #3: Coho Biological Studies, with the specific objective of understanding the effect of climate change on salmon life history with benefit to pre-season forecasts. One of the simplest coho forecast methods involves a sibling regression model, which uses the abundance of returning males (i.e., jacks – fish that return to freshwater after spending only ~6 months at sea) as an indicator of adult returns. These models are based on an association between jack marine survival in the first few months at sea and adult marine survival the following year. The models rely on a stable age structure, an assumption that does not always hold. Marine survival of wild coho salmon in coastal Washington is measured at Bingham Creek, the site of a long-term life-cycle monitoring program operated by the Washington Department of Fish and Wildlife. Marine survival estimates inform pre-season forecasts, and are important in the determination of allowable exploitation rates in bilateral fisheries. Estimates of survival come from release and recovery of coded-wire tagged (CWT) wild coho marked as smolts during the outmigration period and recovered as adults from fisheries and a weir trap. Preliminary analysis established an inverse relationship between rearing streamflow rates and jack survival.
The proposed work will expand on these observations and evaluate the effects of rearing temperature on jack rates. The goal is to make predictions about age-at-maturity by utilizing spatial stream network models of stream temperature (“Thermalscapes”) for the Grays Harbor coho population. The models can be used to hindcast and forecast rearing temperature based on variations in air temperature and streamflow, which allows for analyzing historical data in addition to predicting jack rates under future climate scenarios.
This proposal seeks to expand the Chum SNP baseline to identify fall-, winter-, and summer-run Chum salmon population contributions to mixed fisheries in the Southern Boundary area. Southern Boundary Chum salmon populations have been in general decline yet have recently become a higher priority fishery. Fisheries have shifted to Chum salmon because Chinook salmon have declined and their harvest is restricted. Further, resident Orca Whales, also in decline in Puget Sound, prefer Chinook salmon and are another factor diverting fishing effort to Chum salmon. Several rivers in the Strait of Juan de Fuca and North Puget Sound support Chum salmon, including the Elwha, Nooksack, Snohomish, Skagit, and Stillaguamish rivers. Although wild Chum salmon numbers are low, Tribal and Washington Department of Fish and Wildlife (WDFW) hatcheries maintain Tribal and non-tribal fishing while supporting wild populations. However, because Chum salmon from a hatchery are generally unmarked, we conduct marine fisheries without information on the contributions of specific stocks or hatchery programs to the fishery. Due to the recent elevated importance of the Chum salmon fishery, both the Tribes and WDFW require information to manage fisheries to protect weak stocks and to ensure that fish return to terminal areas. Further, for fisheries in the Southern Boundary area, we need to identify fishery components to adhere to guidelines in the Pacific Salmon Treaty regarding Chum salmon harvest limits by U.S. fishers in relation to Fraser Chum salmon abundance.
This project will identify components of two mixed fisheries over four years to better understand the origins and abundance of wild and hatchery Chum salmon harvested in Strait of Juan de Fuca and North Puget Sound throughout the season.
Producing more hatchery Chinook salmon juveniles has recently been proposed in Washington State with hopes of enhanced ecosystem and fisheries benefits. However, it has recently been shown that even the vast North Pacific Ocean cannot support an infinite number of salmon (Ruggerone and Irvine 2018), and it appears that mortality of salmon in the Salish Sea can also be density dependent (Ruggerone and Goetz 2004). Density-dependent effects between pink salmon in particular (the most numerous species, but also chum salmon) and Chinook salmon have been documented by an increasing number of studies (e.g., Ruggerone and Nielsen 2004; Ruggerone et al. 2003), suggesting that salmon compete for food in the ocean, which can lead to reduced growth, delayed age at maturation, and lower survival rates (Ruggerone and Irvine 2018). Preliminary analyses of the relationships between Chinook salmon hatchery production and numbers surviving to adulthood suggest reduced Chinook survival in years when large numbers of juvenile pink salmon also out-migrate. In some regions, this density-dependent mortality may be so strong that large increases in hatchery releases may limit the number of returning adults.
We propose to evaluate the following questions: what Chinook salmon juvenile release abundance values are associated with greatest marine survival rates? How do survival rates vary with different numbers of juvenile pink salmon out-migrating in the Salish Sea? How do these relationships differ among Chinook salmon stocks from various regions of the Salish Sea?
S19-SP33 Optimization of hatchery Chinook releases in the Salish Sea through ecosystem-based management 2019 Report
The objectives of this project are to 1) identify environmental and biological factors related to variation in marine growth and productivity of Puget Sound Chum salmon (Oncorhynchus keta); and 2) develop stock specific indicators of productivity and survival based on marine growth and environmental indices for forecasting. Previous research examining early marine growth and survival of Puget Sound Chinook salmon (O. tshawytscha) in relation to biological and environmental factors provided an approach to understanding mechanisms related to mortality during the marine period (Campbell et al. 2017, Claiborne et al. in prep). The result of this work is a useful tool used for forecasting fall Chinook salmon in South Puget Sound (WDFW Puget Sound Management Unit, unpublished data).
This proposal will generate early marine growth estimates from scale analysis of archived samples (WDFW Fish Ageing Laboratory) for fall-run Chum salmon for 15 brood years and relate early marine growth to trends in productivity and survival throughout Puget Sound. To assess bottom-up and top-down processes that may be driving variation in productivity, we will examine relationships between marine growth and environmental indices, which will include both large- and regional-scale metrics. For each stock, we will develop predictive models of productivity and survival incorporating environmental indices and annual growth estimates, and use hind-casting to evaluate model performance through time.
S19-SP31 Scale Analysis of Puget Sound chum salmon (Oncorhynchus keta) 2019 Report
Quantifying spatiotemporal change and variability in natural mortality and other population parameters (growth, productivity, etc.) is essential for developing reliable forecasting and assessment models used to manage salmon stocks. Productivity of numerous coho salmon populations in the eastern Pacific has decreased since the 1970’s (Zimmerman et al. 2015), and recent research has identified several factors that may be causing increased mortality in both the marine (Thomas et al. 2017) and freshwater environments (Feist et al. 2017; Ohlberger et al. 2018a). However, there has been minimal effort to incorporate these findings into a rigorous modeling approach that can be used for multiple coho stocks to address fishery, conservation, and ecosystem concerns. We propose to develop spatially explicit hierarchical models for coho salmon stocks, ranging from Oregon to British Columbia. These models will be complete life cycle models, allowing us to evaluate the relative contributions of different factors in space and time.
A better understanding of how drivers such as environmental variation, ecosystem interactions, and fishing pressure have changed over time will also allow us to forecast likely scenarios of future change. By modeling the stocks jointly, and including information about both freshwater and marine drivers of productivity, we aim to address Southern Panel Priority # 3, improving “abundance forecasting and escapement estimation for Coho Management Units (MUs), including better understanding of the impacts of environmental variability and uncertainty.”
This proposal addresses two Southern Panel priorities: genetic stock identification (GSI) sampling of Chum salmon in commercial fisheries and Southern BC and Washington Single Nucleotide Polymorphism (SNP) baseline implementation. This proposal seeks to identify fall-, winter-, and summer-run Chum salmon population contributions to mixed fisheries in Central and South Puget Sound. An initial mixed fishery analysis of the commercial Chum salmon in US Marine Areas 10 and 11 showed that some Chum salmon in the fishery originated in Georgia Strait and the Fraser River (Small et al. 2018a). Further, some Hood Canal summer-run Chum salmon were caught in the fishery; a stock unit of high conservation concern. Because Canadian and summer-run Chum salmon were unexpected in this fishery, this project will identify mixed fishery components of the purse seine fishery over four years to better understand the origins and abundance of Chum salmon populations harvested in mixed fisheries within Puget Sound throughout the season. Up to ten key Chum salmon populations in South and Central Puget Sound will be added to the genetic baseline to enhance the accuracy and precision of mixed fishery analyses in the region. Improved understanding of mixed fishery components will improve fishery management both internationally and domestically.
The outcome of this project will be more thorough representation of Puget Sound Chum salmon populations in the Chum salmon SNP baseline and better understanding of the distribution and abundance of CAN and US fish caught in the Area 10 and 11 fishery. The higher-resolution baseline will be tested with the existing mixed fishery data set from the pilot study (Small et al. 2018a) to identify improvements and to identify populations that may need better representation.
S19-SP13 Puget Sound Chum Salmon GSI 2019 Report
We propose to develop a new class of forecast models for Southern U.S. naturally spawning coho salmon Management Units (MUs) that accounts for possible environmental and demographic effects on the proportion of coho jacks within cohorts. The age composition of southern coho populations consists of jacks — precocious males that mature after ~ 6 months in the ocean — and older males and females that mature after ~18 months at sea. Integrating such information into the sibling relationship may improve forecasts by disentangling the extent to which the observed jack abundance in a given year reflects cohort size, marine survival, and future adult returns versus variation in the age composition. Moreover, previous studies have identified synchronous temporal variation in jack prevalence among southern coho populations at local and regional scales, providing an informative basis by which to coordinate the sharing of information between well-monitored management units and those for which demographic data are sparse.
Recent advances in statistical modelling have given rise to a number of methods for inference and forecasting which account for shared trends and spatially-structured co-variation among populations that have distinct potential for improving forecasts of Southern U.S. coho salmon. We will develop a suite of alternative forecast models using statistical frameworks that incorporate information on spatially structured environmental effects on age-at-maturity (i.e. jack prevalence within cohorts), and evaluate their forecast accuracy to identify the model or set of models with the best performance. Ultimately, this project will generate an alternative preseason forecast framework for coho salmon MUs that will be readily available for use by managers to promote the conservation and sustainable harvest of this culturally iconic and economically valuable species.