Assessing conservation potential of streams for Spikedace and Loach Minnow using species distribution modeling

Abstract

Identifying, evaluating, and prioritizing freshwater systems for conservation is a persistent challenge for managers tasked with conservation and recovery of native fishes. We used historical records from the Gila River basin, the national hydrography dataset, and Random Forest modeling to predict probability of Spikedace Meda fulgida and Loach Minnow Rhinichthys cobitis occurrence throughout their range in the Gila River basin. Models for both species performed moderately well, with relatively high predicted probability of occurrence at streams with historical records. Predicted probability of occurrence was also relatively high in several streams without historical records of focal species, suggesting that there are unoccupied reaches throughout the Gila River basin with similar environmental conditions to historically occupied reaches for both species. Unoccupied reaches with the highest predicted probability of occurrence may have a greater chance of supporting translocated populations of focal species. Our results can be used as a first step for locating reaches most likely to support translocated populations of Spikedace and Loach Minnow within their respective historical ranges. Our approach may be applicable to other species of conservation concern with available historic records in need of population restoration.