Okay, I need to create a concise summary of this article about the decline of coho salmon in California. Let me start by reading through the provided text carefully.
The abstract mentions that coho salmon in California have declined or disappeared from all streams they were historically recorded in. There were up to 582 streams, but only 248 have recent data, with 54% still having them. The farther south, the more likely they've lost their populations. The estimated number of adult coho salmon entering streams in 1987-1991 was around 31,000 per year, with 57% from hatcheries. That means about 13,000 non-hatchery, including naturalized stocks. Now, there are less than 5,000 native coho salmon, many in small populations. The population is down to 6% of the 1940s levels and at least 70% decline since the 1960s. The authors think they should be listed as threatened under state law, possibly endangered under federal.
The introduction talks about the general decline in Pacific Northwest salmonids, including coho. Coho are less abundant than chinook but still important in fisheries. In the 1980s, combined catch was 83,000, with 30,200 in sport. Commercial landings in the 80s averaged 301,000 lb, and 1.6 million in 1976-1979. 1992 was much lower. The southern populations are ecologically significant because they're the southernmost, possibly holding genetic diversity important for the species' future if climate changes.
The authors note that native stocks have declined significantly, with 214 listed as declining. Southern populations are at high risk, while northern ones (except Klamath) are moderate. Historical estimates from the 1940s were 200,000-500,000, down to 100,000 in the 60s, and 30,480 in 1984-85. These estimates are uncertain, but the current data shows a sharp decline.
The paper is a summary of published and unpublished info on distribution and abundance. It's the first systematic assessment of current population status. The goal is to set a benchmark for future comparisons and highlight the need for better data. They also discuss probable causes: stream alterations from poor land use (logging, urbanization), floods/droughts, genetic breakdown, diseases, overharvesting, and climate change.
I need to make sure the summary is detailed but concise. Start with the main points: decline in coho salmon populations in California, historical vs current numbers, factors contributing to decline, and the conclusion about possible endangered status. Mention the key data points like the number of streams, the percentage of native vs hatchery, the 70% decline since 1960s, and the ecological significance. Also, note the economic and ecological importance, and the call for better management data. Avoid any markdown, just plain text in English. Check for any specific terms or numbers that are crucial. Make sure to include the main causes listed in the abstract and the background section. Keep it under the same structure as the original but more condensed. Ensure that all key findings are covered without unnecessary details.
Coho salmon (Oncorhynchus kisutch) populations in California have declined significantly, with native stocks nearly extinct in many streams historically inhabited. Historically present in up to 582 streams, only 248 (43%) now have confirmed recent presence, of which 54% still support coho salmon. Hatchery contributions account for 57% of annual spawning adults, but native populations now number fewer than 5,000 annually, with many in small (<100 individuals) groups. Coho numbers are estimated at 6% of 1940s levels and 70% lower than 1960s totals. Declines are attributed to stream habitat degradation from logging and urbanization, periodic floods/droughts, genetic loss in native stocks, disease, overfishing, and climate change. Southern populations, the species’ southernmost, face higher extinction risk and may hold critical genetic diversity for future adaptation. The authors argue California coho qualify for threatened status under state law, with some populations possibly endangered under federal law. Historical abundance estimates (1940s: 200,000–500,000; 1960s: ~100,000) are unreliable, but current data underscores urgent need for improved monitoring and management to address ongoing population declines.
