A recent article in Science Magazine provides a possible clue as to why the Scott River, a California tributary to the Klamath River, still produces a relatively large amount of coho salmon. A chemical released onto roads as tires wear has been found to kill young coho.1 Watersheds like the Scott River are pristine, sourced directly from springs and snowmelt, with low highway interaction. The Scott contrasts with its neighbor the Shasta river, which runs very close to Interstate Highway 5, and which produces few coho salmon.
Absence of pollution from tire debris may also be part of the reason why Butte Creek is able to produce so many spring-run salmon. On the other side of the coin, the prevalence of roads may help explain why coho salmon have been extirpated from many of the highly urbanized Puget Sound watersheds in Washington State and British Columbia.
The recent study regarding pollution from tires emphasizes the need to protect pristine watersheds like the Scott River, as well as the need to restore those like the Shasta River. There is likely to be more public discussion of this subject in the coming months and years, hopefully as the tire industry seeks alternatives to its problem chemical
- As described in Science Magazine, the chemical is: “a highly toxic quinone transformation product of N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD), a globally ubiquitous tire rubber antioxidant.” ↩