1. Objectives

The Ocean Survival of Salmonids Project is a long-term (20-year) effort. The project monitors salmon and oceanographic conditions in the Columbia River plume and nearshore marine areas. The primary research hypothesis is that “variation in salmon survival during the first few months of ocean residency has the largest impact on cohort strength of all life stages for Pacific salmon.” The primary project objective is “to determine the physical, biological and ecological mechanisms that control survival of salmon during their early marine life.” Hypotheses were grouped into three areas: (a) growth and survival; (b) hatchery-wild interactions and density dependence; and (c) modeling, scenario planning, and recovery.

The primary hypothesis is that marine growth and survival are determined by the combined effects of physical and biological processes in the coastal ocean; the abundance, species composition, and spatial distribution of predators; and the size and availability of salmon and alternative prey.

Because hatchery-wild interactions and density dependence cannot be observed directly, three hypotheses designed to infer the effects of hatchery/wild competition were addressed: (a) there is no difference between the diet and growth of hatchery and wild fish, (b) there is no difference between the distribution and migration timing of hatchery and wild fish, and (c) there is no difference between the synchrony of responses to marine drivers for hatchery and wild fish.

Modeling, scenario planning, and recovery hypotheses are based on assumptions that early ocean growth and survival of juvenile salmon and steelhead are determined through both bottom-up and top-down processes associated with the productivity of coastal ocean and plume habitats during spring and summer. It is also assumed that survival during this period is highly variable and has an exceptionally large impact on cohort strength and, therefore, future adult returns.

While these hypotheses are highly relevant to the Council’s Fish and Wildlife Program, they are difficult to quantify, achieve, and test because of the complexity and unpredictability of the marine ecosystem. A long time-series is needed to tease out the relative impact of many factors.

The project is now in its 20th year, and there is no indication of a specific future end date. The ISRP concludes that this project will continue to provide critical information into the future and that the value of this project to the Fish and Wildlife Program will grow each year. Nevertheless, the program should not remain static. The proponents indicate that they are making efforts to place their results into an ecosystem framework and are modifying the sampling strategy (e.g., via a smaller mesh liner) to provide more information on salmon and their prey simultaneously. These future activities should be reviewed to ensure that the program continues to collect data relevant to management questions, to examine changes in survey methods, and evaluate if the new types of data collection will fill important gaps in understanding of ocean survival (e.g., impacts of forage fish abundance).

One objective is to estimate early ocean survival, but this is not directly addressed. A major question is whether the program can be modified to estimate survival in the early and subsequent ocean life stages (e.g., by the reintroduction of acoustic survey lines).

2. Methods

At present the project is contracted by BPA on an annual basis, with clear milestones for specific work elements such as research vessel cruises as well as sample and data processing.

Juvenile Salmon and Ocean Ecosystem Surveys (JSOES) relies on estuary purse seines to capture salmonids along with measurements of physical and biological characteristics of the Columbia River plume and nearshore ocean. Two additional surveys compare the attributes of hatchery and natural origin juvenile fish (late May), and they characterize the spatial distribution of juvenile salmonids, the pelagic fish community, the salmon prey field, and characteristics of the ocean environment (June). In general, methods are scientifically sound, but some survey methods could be improved. For example, methods currently used are sufficient for collecting biological samples of salmon and associated species in the catch, and for providing indices of relative abundance (i.e., catch per unit effort) but not for directly estimating salmon survival or the abundance/biomass of salmon predators and prey.

A key assumption is that catch per unit effort (CPUE) is proportional to abundance. It is not clear if this been empirically tested using estimates of smolt outmigration from CSS vs. the CPUE from the trawls.

Varying levels of salmon predators add variability to survival proportions. This makes it harder to detect the effects of ocean conditions and also means that models based on earlier years, where the predators were not prevalent, are less and less reliable.

The original trawl survey design was developed primarily to determine the early ocean distribution of juvenile Columbia River salmon. Considering the current hypotheses being tested and the low CPUE of juvenile salmon in surface trawl catches, especially wild salmon, new fisheries-oceanographic ecosystem survey designs (e.g., a gridded survey, larger trawl) and methods (e.g., combined trawl and hydroacoustic surveys) might be considered.

3. Results

The project has made significant progress in addressing a progressive series of questions and hypotheses, ones that have evolved over time as more data are gathered.

Project results show that ocean productivity controls feeding and growth of juvenile salmon (i.e., bottom-up control), leading to multiple, nonexclusive hypotheses about how ocean productivity influences salmon survival. For example, when ocean productivity is high (a) rapid growth allows juveniles to escape size-selective predation and (b) abundant alternative prey for salmon predators reduces predation pressure on salmon juveniles. The investigators conclude, “Importantly, these ocean effects can be somewhat dependent on freshwater effects (carryover effects, Gosselin et al. 2018⁴ ). Therefore, accurately evaluating freshwater management actions requires an accurate ocean context.” An economic analysis may be needed to compare the cost and effectiveness of management actions taken in freshwater (e.g., hydro-system actions) vs. actions occurring in the ocean (e.g., harvest management).

Project results addressing hatchery/wild interactions and density dependence CUs (Critical Uncertainties) were hampered by the low numbers of wild juvenile salmon in ocean research vessel catches because of low relative abundance and/or low sampling rates. Results indicate that hatchery salmon may be used as a proxy for wild salmon in some cases (e.g., migration timing, diets, and spatial distribution), but not others (e.g., size and condition factor). However, data are insufficient to determine “whether hatchery salmon have an advantage over wild salmon during different ocean conditions.”

Project results addressing modeling, recovery, and climate impacts CUs show that “stockspecific distribution, abundance, and survival of juvenile Columbia River salmon in the NCC [Northern California Current] vary synchronously with variable ocean conditions.” Investigators have developed a suite of physical, biological, and ecological indicators of ocean conditions that are useful qualitative predictors of salmon survival that are now being used by managers as early-warning indicators of recent ocean conditions or as covariates in statistical models. Initial results of marine survival modeling “confirm the importance of the marine stage in the salmon life cycle and suggest dramatic declines in population trajectories with a warming ocean.”

An important consideration is whether the project's primary objective (“to determine the physical, biological and ecological mechanisms that control survival of salmon during their early marine life") is sufficient to guide policy or actions that benefit fish and wildlife. Future changes in climate and ocean conditions are not predictable. Thus, as discussed by the investigators in their project summary, a greater emphasis on long term, high quality monitoring of ocean conditions and assessment of changes in the ocean ecosystem that affect juvenile salmon survival is essential.

The project has an excellent publication record with over 121 publications listed. Project findings are shared with others within and outside the basin via numerous journal publications, project reports, conference presentations, an excellent web site, presentations to the Council, and via the Ocean Forum. However, the ISRP notes that communication of information within the Basin will likely decline because there are limitations to project funds to attend conferences and to support other communication portals, such as the Columbia Basin Bulletin.

4. 2017 Research Plan uncertainties validation

The project narrative provided a comprehensive table and text that links its research to 39 CUs, organized into four categories: (a) survival and growth; (b) hatchery wild interactions and density dependence; (c) modeling, scenario planning, and recovery, masking effect of the ocean; and (d) other topics. The project directly addresses six CUs and indirectly addresses 33 additional CUs. Linkage to these CUs is generally appropriate, though Item F3 (What factors within and outside of the Columbia River Basin influence trends in recruitment, mortality, and abundance of Columbia River Basin fish and wildlife populations?) should have been identified as a direct link (current CUs on the web failed to make the link between this CU and the Ocean project).

Table 1 in the narrative identifies several new CUs associated with the project, including 19 new CUs. Information in the project narrative is not always sufficient to understand the new linkages, and additional justification may be needed. For example, some linkages were revised from direct to indirect and vice versa. The indirect relationships identified in Table 1 tend to be more inclusive than exclusive. Some of the linkages may be questionable (G1.1, G2.1, C1.5, F3.7, F3.8, B1, M3.1, F1.4). For example, CU 1.5 states “What are the range, magnitude, and rates of change of natural spawning fitness of integrated (supplemented) populations, and how are these related to management rules, including the proportion of hatchery fish permitted on the spawning grounds, the broodstock mining rate, and the proportion of natural origin adults in the hatchery broodstock?” and it is questionable how surveying juvenile fish in the early ocean period helps answer this CU.

Similarly, it is unclear why CU E2.5: "What additional information is needed to assess the importance of tidal freshwater, estuary, plume, and ocean habitats and their biota on focal species (anadromous salmonids, White Sturgeon, Pacific Lamprey, Eulachon)?" was not included in Table 1, given that CU E2.5 was considered by the Council to be directly addressed by this project in the Council's 2017 database.

⁴ Gosseline, J.L., R.W. Zabel, J.J. Anderson, J.R. Faulkner, A.M. Baptista, and B.P. Sandford. 2018. Conservation planning for freshwater-marine carryover effects on Chinook salmon survival. Ecology and Evolution 8:319-332