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![Map of the study area showing approximate freshwater rearing locations. Symbols represent freshwater release age and colours represent juvenile ocean entry regions associated with the top-ranked model (Table 2). Map projection is WGS84. Made with shapefiles from Natural Earth (naturalearthdata.com). [Colour online.]](profile/Cameron-Freshwater/publication/361394482/figure/fig1/AS:11431281257205474@1719599048482/Map-of-the-study-area-showing-approximate-freshwater-rearing-locations-Symbols-represent.jpg)
Map of the study area showing approximate freshwater rearing locations. Symbols represent freshwater release age and colours represent juvenile ocean entry regions associated with the top-ranked model (Table 2). Map projection is WGS84. Made with shapefiles from Natural Earth (naturalearthdata.com). [Colour online.]
Source publication
The abundance of many Chinook salmon (Oncorhynchus tshawytscha) stocks has declined despite reductions in harvest. We used state-space models parameterized with data from 57 Chinook salmon indicator stocks, ranging from coastal Oregon to southeast Alaska, to quantify long-term (since 1972 release year) changes in juvenile marine survival rate and m...
Citations
... Southern resident killer whales (SRKWs) are one of the smallest populations of cetaceans inhabiting the northeast Pacific Ocean (n = 73) and have been listed as an endangered species under the United States' Endangered Species Act (ESA), and in Canada under the Species at Risk Act (SARA). Diet information from SRKWs suggests a heavy reliance on Chinook salmon (Ford et al. 2016); populations of both hatchery-and wild-origin salmon have experienced fluctuations in both survival and abundance since the 1970s (Freshwater et al. 2022;Ruff et al. 2017). Furthermore, the abundance of large Chinook salmon of older age classes has also declined in populations along the West Coast of North America over the last four decades (Couture et al. 2022;Ohlberger et al. 2018). ...
Effective conservation of threatened populations requires identification of the processes limiting recovery. When multiple population processes are potentially limiting, they are sometimes analyzed independently, often using different datasets. Analytically, this is suboptimal, as processes are often correlated, which can lead to biased estimates of parameters and quantities of interest. Integrated population models (IPMs) can synthesize several data streams in the same probabilistic framework to circumvent these issues. Lack of prey was identified as one of the primary threats to recovery of critically endangered southern resident killer whales (SRKWs), Orcinus orca . Previous studies have correlated SRKW demographic rates with indices of Chinook salmon Oncorhynchus tshawytscha abundance, but these approaches have modeled reproduction and survival independently. We developed an IPM for SRKWs that models both processes simultaneously, as a function of Chinook salmon abundance along the west coast of North America. We used this model to evaluate the relationship between Chinook salmon abundance and demographic rates of SRKWs, with the goal of updating our understanding of a potential causal relationship between prey availability and SRKW population dynamics, and how these relationships may have changed over time. Results suggest that SRKW mortality rates are more strongly associated with Chinook salmon abundance than birth rates. Our analysis also suggests northern resident killer whale abundance could also be affecting SRKW carrying capacity, possibly through competition over shared prey resources. The IPM fit observed total abundance data well and predicted temporal changes in population demographics with reasonable accuracy, but small sample size may have opacified model selection. Our approach offers a valuable tool for predicting the response of the SRKW population to alternative management strategies involving the recovery of Chinook salmon stocks in the eastern Pacific.
... Doutaz et al., 2021;Warkentin et al., 2022). Recent research has revealed distinct survival trends for stream-type and ocean-type stocks even within the same regions (Freshwater et al., 2022), and interior spring Chinook with obligate yearling life histories are also thought to undertake more offshore oceanic migrations, driving differential exposure to North Pacificscale climate changes (Lindley et al., 2021;Weitkamp, 2010). (Healey, 1991;Quinn, 2005;Taylor, 1990 (Weitkamp, 2010). ...
Chinook salmon ( Oncorhynchus tshawytscha , Salmonidae) are foundational to social‐ecological systems of the Northeast Pacific Rim and exhibit a rich diversity of life histories including in their adult migration timing, age at critical life‐history transitions and marine feeding distributions. In recent decades Chinook have experienced declines across much of their native range; however, changes in productivity and abundance have rarely been evaluated in relation to life‐history variation. To understand trends in Chinook salmon production, and how they are related to life history, we compiled time series data from the Fraser River to the Sacramento River on total run size (pre‐fishery abundance) and escapement (post‐fishery spawner abundance) and fit time series models to estimate trends across this bioregion. Our analysis revealed that most Chinook populations are declining, with negative trends in escapement (57 of 79) and total run (16 of 23) size. Trends were most acutely negative for interior spring Chinook in the Fraser, Columbia and Snake Rivers and most populations in California. Summer and fall Chinook had mixed trends, with several summer and fall upriver bright populations in the interior Columbia and Fraser exhibiting increases in abundance from the 1990s to 2019. Our research reveals widespread declines of this important species, but local complexity in trends that are mediated by population‐level life history, migratory behaviours and watershed‐scale restoration actions. Understanding linkages between life histories and resilience should inform rebuilding efforts for Chinook salmon and highlight the need to conserve intraspecific biodiversity.
