Steve Knell and Jeff Shields of the Oakdale and South San Joaquin Irrigation Districts miss some basic facts in their July 19 op-ed calling for predator eradication to help salmon ("Stop studying salmon and start doing something").
Salmon and both native and non-native predator fish coexisted for decades in California with little overall harm to salmon until relatively recently. These days, increased water diversions from the rivers are making salmon more vulnerable to predators than in the past. That's because baby salmon need big, muddy spring runoffs to survive migration from their birth rivers out to the ocean. The turbidity provides a natural camouflage for the baby salmon. Low, clear flows, which have become common in heavily diverted rivers like the Stanislaus, Tuolumne and Merced, give predator fish an unnatural and new advantage they didn't historically have.
More natural and high volume spring outflows help baby salmon not only in the San Joaquin River and its tributaries, but in the delta as well.
executive director, Golden Gate Salmon Association