Biologists Say Predators Eat Half of Salmon, California Farm Bureau Federation Reports

Sierra Sun Times

Boosting flows on San Joaquin River tributaries may not bring the desired benefits to populations of protected salmon—because predatory bass in the rivers apparently eat half or more of juvenile salmon, regardless of river flow, according to studies by a fisheries consulting firm.

The work on the lower Stanislaus River by the firm FISHBIO ties into a long-running debate about whether more water must be retained in the rivers, and therefore unavailable for human use, to benefit protected fish. In late 2018, the State Water Resources Control Board adopted a plan that would require water users to leave “unimpaired flows” of 30% to 50% in three San Joaquin tributaries: the Stanislaus, Tuolumne and Merced rivers.

That plan became the subject of numerous lawsuits, while water districts and government agencies continue efforts to negotiate voluntary flow agreements intended to achieve the same fisheries goals with less-significant water-supply impacts.

Andrea Fuller, senior biologist and principal of FISHBIO, said she and other fisheries biologists have been studying the hypothesis that salmon could be lost to predators “in high numbers.”

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