Using Changes in Naive Occupancy to Detect Population Declines in Aquatic Species; Case Study: Stability of Greenhead Shiner in North Carolina

Determining population trends for many aquatic species is problematic for most resource agencies because little or no historical information is available on population size nor are resources available for contemporary population estimates. Managers often only have available to them presenceabsence data collected by qualitative surveys conducted at intermittent intervals. Changes in naïve occupancy can be used to detect population trends. Naïve occupancy is the ratio of number of sites where a species is detected to total number of sites surveyed, without correcting for imperfect detection. Herein, we present ways to conduct analyses for measuring changes in naïve occupancy using presence/absence data from multiple sources. Required elements include showing measures of uncertainty and statistical analysis (including power analysis). These data can effectively be used to determine population trends for many species in a cost effective and statistically rigorous manner. A case study using the naïve occupancy ratio shows the greenhead shiner (Notropis chlorocephalus) has remained stable from the 1960s to the 2000s.

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