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 at a particular location. In that application the affinity curves can be used to set conservation targets, which are essential for determining a delta smelt management agenda that informs planners when and where environmental conditions need modification and when they do not. Understanding where and when conditions are adequate or inadequate allows managers to develop strategies to conserve delta smelt in the spatially and temporally dynamic upper San Francisco Estuary. The presentation provides the first and to date only comprehensive, data-based treatment of habitat requirements for delta smelt and provides a valuable resource to conservation planners and resource managers.
Hamilton, S.A. and D.D. Murphy. 2020. Use of affinity analysis to guide habitat restoration and enhancement for the imperiled delta smelt Endangered Species Research 43: 103-120.