What is Predation?

Not only is the BO an operationally unsound means of managing New Melones Reservoir, the BO fails to take into account other major factors, like predation, which is a major source of the decline of steelhead.

There are non-native predatory fish in the Stanislaus and San Joaquin Rivers and the Bay-Delta. Research shows that an estimated 95% of the biomass is non-native and a major factor in the loss of steelhead. It is estimated that up to 1 million striped bass live in the Delta and only 1 out of every 10 juvenile salmon reach the Delta. Researchers call it “predation” because these non-native fish prey on the young native fish. Until predation is addressed, native steelhead populations may never increase in the river, no matter how much water is released. The Districts will support legislation that directs the California Department of Fish and Game to eliminate the predatory fish in the Stanislaus.

See video and photos of predation on the Stanislaus River.

Predation – The Real and Solvable Problem

No one knows for sure, not even the experts, what percentage of the decline in native fish is attributable to predation. But the range of even the experts is startling and is an indication that all-is-not-right in the Delta. In a letter from Benjamin Z. Rubin from Nossaman, LLP to the California Department of Fish and Game (CDFG) Commission president on March 31, 2010, he cites to the Commission deposition testimony from CDFG’s own experts on the devastation of predation. These experts include Marty Gingras, Department Biologist, who estimates 5%-25% predation on winter run; Matthew Nobriga estimates 6%-50% predation on winter run; Dr. Charles Hanson, Independent Biologist, pegs it at 21% predation; David Kohlhorst, Former Department Biologist, thinks it is 30% predation.

Recently the National Marine Fisheries has been thinking along the same lines. They are experts and have begun telling CDFG to remove the take limits, the size limits and the season limits on striped bass. While all numbers are variable, the EXPERTS believe it’s somewhere south of 50%.

Stripers and other predatory fish are not the only reason for the decline in the native fish in the Stanislaus River, but they are a major factor that is unrelated to the amount of water that goes down the river. If we are truly serious about saving the native fish, something needs to be done about the Striped Bass.