Fraser River Pacific salmon have declined in recent decades possibly from parasitism by sea lice (Caligus clemensi and Lepeophtheirus salmonis). We describe the abundance of both louse species infesting co-migrating juvenile pink (Oncorhynchus gorbuscha), chum (O. keta), and sockeye (O. nerka) salmon over five years in the Discovery Islands and Johnstone Strait, British Columbia. The generalist louse, C. clemensi, was 5-, 7-, and 39-times more abundant than the salmonid specialist, L. salmonis, on pink , chum, and sockeye salmon, respectively. Caligus clemensi abundance was higher on pinks (0.45, 95% CI: 0.38-0.55) and sockeye (0.39 95% CI: 0.33-0.47) than chum. L. salmonis abundance was highest on pinks (0.09, 95% CI = 0.06-0.15). Caligus clemensi had higher abundances in Johnstone Strait than the Discovery Islands. These results suggest differences in host specialization and transmission dynamics between louse species. Because both lice infest farmed salmon, but only C. clemensi infests Pacific herring (Clupea pallasii), conservation science and management regarding lice and Fraser River salmon should further consider C. clemensi and transmission from farmed salmon and wild herring.

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Data mobilization—the process of making data available for appropriate re-use—remains a key barrier in effective salmon management. Data mobilization facilitates data sharing, discovery and reuse, and leads to increased citations, synthesis data products, meta-analyses and robust management-decision support-tools. The International Year of the Salmon High Seas (IYS) Expeditions in 2019, 2020, and 2022 presented a challenge and opportunity for data mobilization efforts due to the scale, volume, diversity of data, and number of nations involved. Here we demonstrate how we mobilized this salmon ocean ecology data—given the international scope of the project—through a natural alignment to the United Nations’ Global Ocean Observing System and Decade of Ocean Science for Sustainable Development. Under this framework datasets were catalogued using metadata records, assigned digital object identifiers, and published to a web accessible data catalogue (https://iys.hakai.org). Where possible, pre-existing community-developed and international data and metadata standards were adopted and data were also published in global open-access repositories. Both the sociocultural and technical solutions implemented deepen the impact of the IYS and lay a foundation and clear path forward for salmon and oceanographic data producing institutions, commissions, foundations, or projects interested in contributing to international data-intensive salmon and oceanographic sciences.

Migrating marine taxa encounter diverse habitats that differ environmentally and in foraging conditions over a range of spatial scales. We examined body (RNA/DNA, length-weight residuals) and nutritional condition (fatty acid composition) of juvenile sockeye salmon (Oncorhynchus nerka) in British Columbia, as they migrated through coastal waters that varied oceanographically over tens of kilometers. Fish were sampled in the stratified, productive northern Strait of Georgia (NSoG); the highly mixed, unproductive Johnstone Strait (JS); and the transitional zone of Queen Charlotte Strait (QCS). Body and nutritional condition responded rapidly to changes in prey availability and were lowest in JS with low prey availability, supporting the Tropic Gauntlet Hypothesis, additionally we saw signs of compensatory growth in QCS. Juvenile salmon leaving the SoG in 2016 had significantly lower condition than in 2015, despite higher zooplankton biomass in 2016. We propose that this was due to the higher abundance of low food quality southern zooplankton species in 2016. This study highlights the importance of including food quality as a parameter to understand changes in fish condition and survival between years. Furthermore, small scale variation in oceanographic dynamics impact foraging conditions and need to be considered when assessing early marine survival of juvenile salmon.

Migrating marine taxa encounter diverse habitats that differ environmentally and in foraging conditions over a range of spatial scales. We examined body (RNA/DNA, length-weight residuals) and nutritional (fatty acid composition) condition of juvenile sockeye salmon ( Oncorhynchus nerka) in British Columbia, while migrating through oceanographically variable waters. Fish were sampled in the stratified northern Strait of Georgia (NSoG); the highly mixed Johnstone Strait (JS); and the transitional zone of Queen Charlotte Strait (QCS). In 2015, body and nutritional condition were high in the NSoG but rapidly declined to reach lowest levels in JS where prey availability was low, before showing signs of compensatory growth in QCS. In 2016, juvenile salmon had significantly lower condition in the NSoG than in 2015, although zooplankton biomass was similar, condition remained low in JS, and no compensatory growth was observed in QCS. We provide evidence that differences in juvenile salmon condition between the two years were due to changes in the food quality available to juvenile fish. We propose that existing hypotheses about fish survival need to be extended to incorporate food quality in addition to quantity to understand changes in fish condition and survival between years.