Estimating the Size of Historical Oregon Salmon Runs

Abstract

Increasing the abundance of salmon in Oregon's rivers and streams is a high-priority, public policy objective. Salmon runs have been reduced from predevelopment conditions (typically defined as prior to 1850), but it is unclear by how much. Considerable public and private resources have been devoted to restoring salmon runs, but it is uncertain what the current recovery potential is because much of the freshwater and estuarine habitat for salmon has been altered and there is no expectation that it will be returned to a predevelopment condition. The goals of all salmon recovery efforts are based on assumptions about the size of the runs prior to significant habitat alteration, coupled with an estimate of the amount and quality of freshwater and estuarine habitat currently available. We estimated the historical aggregate salmon run size in rivers along the Oregon coast (excluding the Columbia River) using two methods: (1) converting estimated aboriginal population levels into numbers of salmon; (2) extrapolating cannery pack into numbers of salmon. Annual aboriginal harvest of all salmon species is estimated to have been approximately 10 million pounds per year (4,500,000 kg) or 1.75–5.36 million salmon, a harvest level similar to that occurring during the height of commercial fishing on Oregon's coastal rivers in the late 1800s and early 1900s. Extrapolating cannery pack data, the estimated size of the late 1800s aggregate runs of coho salmon (Oncorhynchus kisutch) was 1.5–2.5 million. The estimated size of aggregate runs of chinook salmon (Oncorhynchus tshawytscha) runs was 290,000–517,000. Compared to our estimates of mid-1800s coho salmon levels, early 2000 runs (during favorable ocean conditions), were 11–19% of the historical level. During poor ocean conditions (1990s), current coho salmon runs were 3–6% of the historical size.