This is the fourth post in the NiCHE series Animal Encounters, edited by Heather Green and Caroline Abbott. You can read all posts in this series here.
Pacific salmon (Oncorhynchus spp.) are an abundant group of fishes whose distribution extends north from California to Alaska, and south from Russia to Japan. For thousands of years, salmon have fueled ecosystems and played a vital role in the cultural richness of Indigenous Peoples throughout their range. Over the last century and a half, these fishes have supported a lucrative commercial fishery. Yet salmon populations in Canada and the Pacific Northwest have undergone a substantial decline in abundance and diversity over recent decades such that commercial fisheries across this broad region now are a mere shadow of their former dominance. While much of the loss in Pacific salmon over recent decades is relatively well documented, an understanding of salmon’s richness in the deeper past remains veiled by the fog of human memory and colonial conquest.
Such is the plight of wild species and populations the world over; we have all but forgotten how abundant and widespread many animals were a mere century ago. For example, the now extinct passenger pigeon was at one time considered the world’s most numerous bird, estimated at three to five billion individuals.1 Yet, we have forgotten how their annual migrations once eclipsed the sun. Likewise, in 1871, bison outnumbered humans in North America; a single human generation later, this once-abundant animal of grassland ecosystems was decimated to near extinction. We tend to measure such changes in abundance or distribution of species over a few decades at most, for we rarely have the archival information required to assess these changes over the entire period of human influence. This “ecological amnesia,”2 as Wade Davis terms it, can lead to a “shifting baseline syndrome,”3 whereby abundances in recent decades are incorrectly assumed to be the appropriate baselines against which to estimate the changing state of nature. The confluence of these phenomena can impair the characterization of risk to wildlife, hide a legacy of stressors, and delay conservation action.4
Fig. 1, left: notebooks from the Skeena Collection. Fig 2, right: Scale book notes. Images courtesy of Michael Price.
Fortunately, researchers in the early 1900s began collecting the scales — the literal body armor of fish — and biological information of salmon caught in Canadian commercial fisheries. As early as 1903, there was notable public outcry for the decrease in number of sockeye salmon (O. nerka) returning to rivers in British Columbia.5 Sockeye was the first marketable salmon sold in cans, and has remained the most economically-lucrative species on the Pacific coast. In 1911, the British Columbia Provincial Fisheries Department hired a young Stanford University professor, Dr. Charles Gilbert, to better understand the fundamental life history of sockeye and the potential impacts of commercial fisheries.
Dr. Gilbert had pioneered the art of reading fish scales as had been performed for trees: counting the concentric rings of the scale to determine the age of each fish. By the following year, Dr. Gilbert had begun research programs for sockeye salmon in four regions of British Columbia where these fishes returned en masse: the Fraser River, Rivers Inlet, Skeena River, and Nass River. Over the next thirty five years, fisheries inspectors would make weekly visits to salmon canneries and examine two hundred or more fish caught by a fleet of wooden row boats. In their black notebooks, they’d mark the date of capture, length, mass, and sex of each fish, then scrape a glob of scales with a butter knife and smear them onto the page. At the end of each season, the notebooks would be shipped to California for Dr. Gilbert to age with a microscope. The resulting information was then transcribed into annual reports for fishery managers to ponder, and the notebooks buried in boxes for untold time to discover.
And so it was. This biological treasure chest and literal window into the past was eventually unearthed and re-explored using modern scientific tools a century later. Dr. Skip McKinnel, a retired research scientist and self-proclaimed “history buff,” rediscovered the scale collection in the basement of Vancouver’s Pacific Salmon Commission building after a year-long search. The opportunity to better understand the last century of change in wild salmon had arrived. Unbeknownst to Dr. Gilbert, the slime that was scraped with each glob of scales held the genetic signature of its host fish, which when analyzed, revealed the source population – where each fish originated. As such, we’ve since learned just how abundant and diverse individual populations of sockeye were one hundred years ago, and how these populations shifted in their varying proportions over decadal time periods. For instance, having now analyzed some seven thousand scales (and so, seven thousand individual fish) from the Skeena River collection, it is apparent that wild sockeye populations have declined by ~75% over the last century: some have declined more than others.6 Indeed, populations of larger- bodied fish have declined the most, indicating that the cause of decline was likely size-selective capture imposed by commercial gill-net fisheries. Population diversity has similarly declined over the last century by ~70%: the historically diverse population portfolio — composed of numerous, abundant sockeye populations that once stabilized the watershed – has simplified and weakened.7
Modern tools combined with archival collections can help us understand broader questions based on the stories of individual fish. For example, how have salmon populations responded to climate change over the last century, and how might they respond to future change? Peel back a page within any one of the five fisheries notebooks collected in 1913 for a glimpse. Fish number 120 is at the top of the page, a female of larger-than-average size, captured on August 5th when the fishing boats were concentrated at the mouth of the Skeena River. Though the scales have hardened over the century, they are extracted off the page with relative ease: one is placed under a microscope for aging and measuring, several more are deposited in a vial for the genetics lab. She was in her sixth year when caught, having spent two in a freshwater lake followed by three in the ocean. We know this because of the ring pattern. Similar to a tree, age is calculated by adding the annual rings: growth is slow during winter, and forms a dark band – the rings then spread wider during summer when growth is higher. She was born and raised in Wedzin’ben (Morice Lake), the ancestral territory of the Wet’suwet’en Peoples. The genetics lab matched her unique signature with the existing population – where adults spawn in the gravels of submerged shoreline and juveniles feed in the shallows. Like other sockeye from Wedzin’ben caught during this early period, her growth in the lake was slower than fish in recent decades. When combined with climate data recorded over the last century, we now see that the growth of fish rearing in Wedzin’ben is increasing in response to warming temperatures associated with climate change. But not all sockeye populations and their nursery lakes in the Skeena are responding positively to shifts in temperature.8 Some will benefit from a future of change, while others may not.
The recovery of data from collections such as this ultimately can rescue stories of change. Dr. Gilbert’s notebooks and those like them provide a deeper understanding of the current state of wild populations, are helping to identify the factors responsible for diminished abundances, and allow us to more accurately evaluate the risks posed by humans; all of which contribute to forming more comprehensive strategies for conservation and recovery of at-risk populations.9 While those old fisheries notebooks saw the dramatic changes to wild salmon coming, the ongoing collection of fish scales – such as those currently undertaken by Indigenous Fisheries programs in salmon strongholds like the Skeena – will enable the story of such changes to be told.
Notes
1 Murray, G.R., Soares, A.E.R., Novak, B.J., Schaefer, N.K., Cahill, J.A., Baker, A.J., Demboski, J.R., Doll, A., Da Fonseca, R.R., Fulton, T.L., Gilbert, M.T.P., Heintzman, P.D., Letts, B., McIntosh, G., O’Connell, B.L., Peck, M., Pipes, M-L., Rice, E.S., Santos, K.M., Sohrweide, A.G., Vohr, S.H., Corbett-Detig, R.B., Green, R.E., and Shapiro, B. 2017. Natural selection shaped the rise and fall of passenger pigeon genomic diversity. Science 358: 951–954.
2 Davis, W. 2018. Ecological amnesia. In: Memory. Editors: Tortell, P., Turin, M., and Young, M. pp. 21-30. UBC Press, Vancouver, BC.
3 Pauly, D. 1995. Anecdotes and the shifting baseline syndrome of fisheries. Trends in Ecology and Evolution 10: 430-430.
4 Soga, M., Gaston, K.J. 2018. Shifting baseline syndrome: Causes, consequences, and implications. Frontiers in Ecology and the Environment 16: 222-230.
5 Babcock, J.P. 1903. Report of the fisheries commissioner for British Columbia for the year 1903. Victoria, BC.
6 Price, M.H.H., Connors, B.M., Candy, J.R., McIntosh, B., Beacham, T.D., Moore, J.W., and Reynolds, J.D. 2019. Genetics of century-old fish scales reveal population patterns of decline. Conservation Letters 12: e12669.
7 Price, M.H.H., Moore, J.W., Connors, B.M., Wilson, K.L., and Reynolds, J.D. 2021. Portfolio simplification arising from a century of change in population diversity and artificial production. Journal of Applied Ecology 58: 1477-1486.
8 Price, M.H.H., Moore, J.W., Connors, B.M., McKinnell, S., and Reynolds, J.D. 2024. Habitat modulates population-level responses of salmon growth to a century of change in climate and competition. Global Change Biology 30: https://doi.org/10.1111/gcb.17095.
9 Buxton, R.T., Nyboer, E.A., Pigeon, K.E., Raby, G.D., Rytwinski, T., Gallagher, A.J., Schuster, R., Lin, H-Y., Fahrig, L., Bennett, J.R., Cooke, S.J., and Roche, D.G. 2021. Avoiding wasted research resources in conservation science. Conservation Science and Practise 3: 1-11.
Header image: Sockeye chase, Skeena Wild Conservation Trust (SWCT). Image courtesy of Michael Price.
