Author: Cal Water

In a recent Comment in these pages, five researchers affiliated with the University of California, Davis critiqued a biological opinion issued by the U.S. Fish and Wildlife Service (FWS) under §7(a)(2) of the Endangered Species Act (ESA) that analyzes the effects of ongoing operations of the Central Valley Project (CVP) and State Water Project (SWP) on the Delta smelt. The subject is consequential because the Delta smelt’s historical habitat has been transformed and severely degraded since the California Gold Rush, leading to a significant decline in the size of its population; and because the CVP and SWP are far and away the two largest water supply projects in California, delivering […]
The habitat for any species results from a complex interplay of the environmental conditions that meet the resource needs of each of its life stages. In this paper, available data on water clarity, temperature, salinity, prey, and water body type are used to specify ranges of suitable conditions for delta smelt through its life cycle. The authors develop “affinity curves” that portray the adequacy of environmental conditions for each life stage. The curves are fundamentally important in guiding conservation management decisions for delta smelt. They depict, for example, when salinity is too low or too high for delta smelt to develop and how much food is sufficient to keep them feeding […]
The use of surrogates in conservation planning is commonplace in California and elsewhere.  A substantial body of empirical literature has demonstrated the limited effectiveness of surrogates as management tools unless it is first established that the target species and surrogate will respond similarly to a given set of environmental conditions.  We explain that, while the National Marine Fisheries Service historically used hatchery Chinook salmon survival data as a surrogate for wild Chinook salmon, steelhead, and green sturgeon survival, it erred by doing so without first validating that the surrogate responds in the same manner to environmental conditions as the target species.  The consequence of use of surrogates absent validation is […]
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