Six years ago, scientists in the Pacific Northwest untangled a mystery about why salmon were dying in the region, often in astonishing numbers — with as many as 90% of the migrating adult coho salmon perishing in parts of Puget Sound. The culprit turned out to be a toxic chemical from tires washing into waterways. Now, some of the same researchers that made the 2020 discovery have confirmed that this tire-derived compound is present, at worrisome levels, in salmon-bearing watersheds in California. A study published last month in the journal Environmental Science and Technology Letters finds that at least 10 rivers and creeks in the Bay Area and Santa Cruz region have had potentially lethal concentrations of the chemical 6PPD-quinone after stormwater flowed into them. … [F]ive of the California rivers and creeks that logged harmful levels of the toxic substance are federally designated as “critical habitat” for endangered coho.

Other salmon news:

• Daily Republic (Fairfield, Calif.): Reclamation holding workshop for Central Valley salmon
• Wall Street Journal: Lasers, robots and AI: The fight to save salmon goes high-tech