Understanding the state and trends in spawner abundance is important for salmon conservation because these salmon are available to meet ecological needs within watersheds and can reproduce and contribute to future generations.
Total abundance represents spawners plus catch, and provides additional information on the total number of salmon that survive to maturity. Total abundance is representative of the capacity of the population to reproduce, although those salmon removed by fisheries do not actually contribute to future generations.
Total abundance is more difficult to calculate at the regional scale because salmon caught in ocean fisheries may comprise fish destined to spawn in more than one river, or even more than one region, and additional genetic data are often required to assign catch to specific rivers or regions.
Widespread declines in commercial catches of Pacific salmon in Canada since the mid 1990s have meant that total abundances (spawners plus catch) have generally declined more than spawner abundances. In some cases, such as Yukon Chinook, total abundance began to decline much earlier and more dramatically than spawners, but reductions in catch were not enough to stem declines in spawners that have followed. In other cases, such as Fraser coho, we have seen spawner and total abundances recover following reductions in commercial harvest, however total abundances have tended to decline again when harvest is increased.
We include the broadest available time period of data in our assessments, and the length of time series that we use for each species and region depends on the available data. Spawner survey data of individual rivers documented in DFO’s New Salmon Escapement Database generally starts around 1950, while many of the other datasets (e.g. from the Pacific Salmon Commission) began in the 1970s and 1980s when salmon fishing was at its peak and there was increasing reliance on monitoring and data to inform fisheries management - including international treaties. The longest time series is for Fraser sockeye, which starts in 1893!
We used the most up-to-date information available for each region and species but because those data are held and processed by different agencies and offices, the delay from data collection to public release may vary from days, to months or even years.
Data are sometimes withheld if they are being used by DFO to provide science advice that has not yet gone through a formal review process. In most cases, if we show data that have been collected within the last 12 months, those data should be considered preliminary as they are likely under review by DFO and/or technical committees under the Pacific Salmon Commission.
There are many reasons why the current state we report may not be consistent with anecdotal reports or media stories about salmon in your area.
This State of Salmon report focuses on aggregate abundance at the regional scale, but salmon populations in different rivers within a region may be doing different things. For example, the Vancouver Island & Mainland Inlets region is quite large, and although Chinook salmon at the regional scale are doing quite well, specific groups of salmon within the region are doing poorly and are of conservation concern (e.g. West Coast Vancouver Island Chinook). These differences highlight both the different pressures that salmon can face within a region and the different ways that salmon populations may respond to pressures due to their genetic and life-history diversity.
We also focus our analysis on average abundances over the generation length of the species, which reduces the influence of dominant return years or random fluctuations in salmon abundance on status outcomes†. However, this means that sudden, dramatic changes in abundance (e.g. a record high return in one year) may not be reflected as strongly in the generational average.
Finally, most people tend to consider the state of salmon relative to their memory or what they have seen or experienced in their lifetime. Salmon returns may be better than last year, or even than the last 10 years, but when we look further back in time we may see that total abundances are still much lower than they were historically. This human tendency to focus on how things have changed on shorter timescales contributes to something called the “shifting baseline” whereby our perception of status tends to slip with each generation as salmon abundances decline over time†. In an attempt to avoid shifting baselines, we use a historical baseline based on all available years of data - but we also recognize that the time series are relatively short for many of these species and other types of information such as intergenerational Indigenous Knowledge suggests that declines may be more dramatic that the scientific record suggests.
Our analyses of abundance include both wild and hatchery fish. Hatchery production can be a major contributor to the numbers of salmon, particularly Chinook and coho, returning to certain rivers where hatchery releases occur.
For rivers with major hatchery operations, there may be monitoring of returning spawners using Coded Wire Tags that separate wild and hatchery fish, but it is difficult to make this distinction at the broad, regional scales that we considered. Due to the challenges separating hatchery-origin fish at the regional scale for all species, we do not remove hatchery fish when assessing the state of salmon.
It is well established that hatcheries tend to have negative impacts on wild salmon populations due to, for example, the potential for adverse genetic effects, competition, increased fishing pressure, and disease†.
Hatcheries aim to increase the abundance of salmon, often to improve fisheries, and thus may increase total abundance. When hatcheries are operated with conservation objectives, they may also increase spawner abundance, although the quality and diversity of spawners may be adversely impacted.
Steelhead share a recent common ancestor with Pacific salmon and thus have the same genus name - Oncorhynchus. You can think of Pacific salmon species (Chinook, chum, coho, pink, sockeye) as being siblings and steelhead as their cousin.
Steelhead share the same life history as Pacific salmon - they rear in freshwater, migrate to the ocean to grow as adults, and return to their natal stream to spawn. For example, salmon typically die after they spawn, but steelhead can spawn multiple times. Repeat spawners are relatively rare, but can complete a full migration from their natal streams to the ocean and back again up to four times during their lifetime.
Learn more about steelhead status in British Columbia.
The regions reflect major drainage basins in British Columbia and the Yukon (e.g. Fraser, Nass, Skeena) or an aggregate of smaller coastal watersheds that share similar geographic and environmental characteristics (e.g. Central Coast, Haida Gwaii).
Our assessment of the State of Salmon takes a data-driven approach that is based in Western Science, and represents just one way of knowing how salmon are doing.
Indigenous Knowledge is contemporary and historical knowledge derived from the individual and collective experiences, traditions, and culture of Indigenous People†. Indigenous Knowledge is place-based, meaning that it cannot be separated from the lands and waters where it has been learned, and inter-generational, meaning it is passed down through generations. As such, Indigenous Knowledge can provide a deep understanding of how salmon have changed over decades or even centuries but cannot be simply summarized over broad geographic regions.
For many regions and species, the scientific record is relatively short and may not adequately represent changes in abundance that have undoubtedly occurred over centuries of colonization, settlement, and human development. However, these data represent a type of information that can be relatively easily compiled, analysed, and compared across broad spatial scales.
We are working to understand ways in which we can meaningfully incorporate Indigenous Knowledge into our narrative on the State of Salmon that respects and recognizes the diversity of Indigenous cultures and perspectives throughout the range of Pacific salmon.
Even- and odd-year returns of pink salmon are often treated separately in fisheries models and management because pink salmon have a fixed two-year life cycle and thus even- and odd-year populations in the same region or river do not interbreed.
Often, one lineage will return in much higher abundance than the other year. For example, pink salmon in the Fraser River are “odd-year dominant” with far fewer pink salmon returning to spawn in even years. We report the current state and trends for smoothed time series of abundance. For pink salmon this is a running-two year average that smooths out even or odd-year dominance. This approach avoids having large changes in state from year to year for pink salmon and allows for more meaningful comparisons in state and trends among regions and species.
© Pacific Salmon Foundation 2024 | BN: 11907 5638 RR0001
This report is a product of the Pacific Salmon Foundation. Read more about PSF’s work at psf.ca
© Pacific Salmon Foundation 2024 | BN: 11907 5638 RR0001
This report is a product of the Pacific Salmon Foundation. Read more about PSF’s work at psf.ca