Salmon and Steelhead Abundance in the Columbia River in the Nineteenth Century

I estimated peak runs of Pacific salmon Oncorhynchus spp. and steelhead Salmo gairdneri in the Columbia River during the 40 years centered on 1900 on the basis of peak-period commercial catches and probable optimum exploitation rates. Peak-period catches were estimated from mean catch weights during the five consecutive years of greatest total harvest, and from mean weights of fish reported in the early literature. These catches were 1,700,000 summer chinook salmon Oncorhynchus tshawytscha (1881–1885), 382,000 steelhead (1892–1896), 1,100,000 fall chinook salmon (1915–1919), 400,000 spring chinook salmon (approximately), 476,000 coho salmon O. kisutch (1894–1898), 1,915,000 sockeye salmon O. nerka (1883–1887), and 359,000 chum salmon O. keta (1915–1919). Optimum harvest rates for maximum sustained yield from nonhatchery stocks were obtained from literature: 0.77 for coho salmon, 0.73 for sockeye salmon, 0.68 for spring and summer chinook salmon, 0.88 for fall chinook salmon, 0.69 for steelhead, and 0.48 for chum salmon. Peak-period runs estimated from optimum harvest rates were 2,623,000 sockeye salmon, 4,338,000 chinook salmon, 618,000 coho salmon, 554,000 steelhead, and 748,000 chum salmon–8,881,000 adults altogether. On the basis of the more probable harvest rates that produced overfishing (0.80–0.88), total run size was about 7,505,000 adults, a single best estimate of total predevelopment runs. I discuss aboriginal catch in relation to the theory that decimation of Indian populations after 1800 permitted salmon and steelhead stocks to expand. Using the shape of stock-recruitment functions and appropriate commercial harvest rates, I support the alternative hypothesis that salmon stocks actually decreased in the early 1800s with decreased Indian harvest, then increased after 1850 as commercial fisheries developed, and finally decreased in response to overfishing. Environmental degradation exacerbated the latter decrease.