In our last installment, Controlling Invasive Species, we pointed out the presence of and significant adverse impacts invasive species have on the Delta and struggling native fish populations. In particular, non-native predator fish pose an equally significant threat. And, as with many other harmful invasive species, far more work must be done to understand and control their impacts.

For too long, California’s fishery regulators have struggled with the direct conflict between protecting native endangered species and efforts to enhance sport fishing opportunities in the state. The ongoing struggle in the Delta between bass and salmon is a major case in point. The Department of Fish and Wildlife (DFW) and appointed Fish and Game Commission (FGC) have been slow to address the problem of predation by striped and black bass on native, endangered salmon and delta smelt over an apparent concern that sport fishing enthusiasts will not be happy. As a result, the Delta has become a world class bass fishing destination at the expense of California’s iconic native salmon.

“If present trends continue, native fishes in the Delta will be replaced largely by alien species such as wakasagi smelt, Mississippi silversides, and largemouth bass… Fisheries for largemouth bass and other warm-water fishes will expand, dominating the system even more than today.”

-Peter Moyle, Professor Emeritus at the University of California, Davis and is Associate Director of the Center for Watershed Sciences

Predators such as striped and black bass are estimated to kill 9 out of every 10 juvenile salmon before they even reach the Delta. These voracious feeders also hamper salmon recovery efforts by feasting on recently released hatchery salmon smolts. Every fishery expert recognizes it is a problem, including the National Marine Fisheries Service (NMFS) who identifies predation by non-native fish as a major threat to endangered salmon.

Despite efforts to adjust fishing regulations, the voracious predators are still being protected by state officials. In the past, California Fish and Game Commissioners have declined to change size and bag limit regulations as a means for controlling these predators due to perceived scientific uncertainty. As we said in Managing Science, Uncertainty and Risk in the Delta, the next administration must move beyond the endless discussion about absolute scientific certainty and implement adaptive management actions to begin to find solutions in the Delta. The bass are here to stay, but selectively removing and controlling these predators in critical areas of the Delta and its watershed to improve salmon survival rates must be undertaken. Effective actions to reduce predation must be part of the broader ecosystem management approach we have advocated for.

We are encouraged by recent efforts initiated by the DFW and FGC to update archaic Delta fishery policies and to begin to find management solutions that will actually address predation. The next Governor must continue this important work and implement policies that appropriately prioritize native species over non-native species.