Are wild chinook salmon extinct in the American River?

Thousands of chinook salmon spawn in the lower American River every fall and the numbers are up nicely this year, so why suggest that wild chinook are extinct there? Sadly, there is good evidence that salmon spawning in the river are hatchery fish, or progeny of hatchery fish. Natural spawning produces many juveniles, but not enough adults to keep a population going....

Finally, in 2007, Fish and Game began marking 25 percent of hatchery fish by clipping off their adipose fins before they're released (adipose fins are small, fleshy fins near the tail). The clipped fish are also given tags that identify the hatchery and release group. This is a standard and widely used method. In the Central Valley, all hatchery winter, spring and late fall chinook are tagged, as are all fall chinook from the small Merced River Hatchery, and all hatchery steelhead. Fish and Game crews now also check carcasses for adipose fins, and keep track of the numbers with and without the adipose fins. By 2010, 25 percent of essentially all hatchery fall chinook were marked, so multiplying the percentage of fish without adipose fins by four estimates the percentage of hatchery fish.