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Small Populations in Jeopardy: A Delta Smelt Case Study

September 2020

Citation: ELR 10714

Author: Karrigan Börk, Peter Moyle, John Durand, Tien-Chieh Hung, and Andrew L. Rypel

Under §7 of the Endangered Species Act (ESA), federal agencies must ensure that actions they authorize, fund, or carry out are “not likely to jeopardize the continued existence of any endangered species or threatened species or result in the destruction or adverse modification of habitat of such species.” For species with low and declining populations, applying this standard is legally and scientifically difficult. The U.S. Fish and Wildlife Service (FWS) faced this problem in its recent biological opinion (BiOp) analyzing impacts to threatened Delta smelt from water project operations in the California Delta. FWS concluded the “species’ recent abundance trends strongly suggest it is in the midst of demographic collapse,” and most recent surveys to locate smelt have failed to find them. Nevertheless, FWS approved agency actions that will likely increase extinction risk for Delta smelt. This Comment illustrates, through a case study of the Delta smelt BiOp, the difficulties in making ESA jeopardy determinations for species on the brink of extinction, and concludes that the myriad challenges inherent in conservation of some small and declining populations make reasoned §7 analysis difficult, bordering on impossible.

Karrigan Börk is an Acting Professor of Law at the UC Davis School of Law and an Associate Director at the UC Davis Center for Watershed Sciences. Peter Moyle is a Distinguished Professor, Emeritus, in the UC Davis Department of Wildlife, Fish, and Conservation Biology and an Associate Director at the UC Davis Center for Watershed Sciences. John Durand is a Professional Research Scientist at the UC Davis Center for Watershed Sciences. Tien-Chieh Hung is an Assistant Adjunct Professor of UC Davis Department of Biological and Agricultural Engineering. Andrew L. Rypel is an Associate Professor and the Peter B. Moyle and California Trout Endowed Chair, UC Davis Department of Wildlife, Fish, and Conservation Biology and Acting Director at the UC Davis Center for Watershed Sciences.

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