SAN FRANCISCO (AP) — Baby salmon are dying by the thousands in one California river, and an entire run of endangered salmon could be wiped out in another. Fishermen who make their living off adult salmon, once they enter the Pacific Ocean, are sounding the alarm as blistering heat waves and extended drought in the U.S. West raise water temperatures and imperil fish from Idaho to California.

Hundreds of thousands of young salmon are dying in Northern California's Klamath River as low water levels brought about by drought allow a parasite to thrive, devastating a Native American tribe whose diet...