The Direct Impacts of Non-Native Species on Pahrump Poolfish, Empetrichthys latos latos

Authors: Brandon Paulson, Craig Stockwell

Year: 2018

Abstract

Desert fishes that evolved in simple communities, are hypothesized to be vulnerable to non-native species introductions. Such is the case for the Pahrump Poolfish, Empetrichthys latos latos, whose conservation has been frustrated by colonization of invasive species including both Red Swamp Crayfish, Procambarus clarkii, and Western Mosquitofish, Gambusia affinis, in refuge habitats. We examined the direct effects of crayfish and mosquitofish on poolfish adult survivorship, and juvenile recruitment under semi-natural conditions in 300-gallon mesocosms. We found that allopatric poolfish populations had significantly higher adult survival (95.6%.03%) than when held in sympatry with crayfish (53.1%.16%; z = -3.2; p < 0.005) or when sympatric with crayfish and mosquitofish (55.1.21%; z = -2,98; p < 0.010). Crayfish had no effect on poolfish juvenile recruitment (17.54.12 juveniles per adult) compared to juvenile recruitment for allopatric poolfish populations (13.611.74 juveniles per adult; z=.6; p > 0.05). However, the combined effects of crayfish and mosquitofish led to significant declines in juvenile recruitment (0.47.13 juveniles per adult; z = -2.79; p = 0.015). These results mimicked earlier experiments that showed severe impacts of mosquitofish on poolfish juvenile recruitment (Goodchild & Stockwell 2016, Trans. Am. Fish. Soc. 145 (2); 264-268). Thus, our findings combined with earlier work may explain how poolfish have co-persisted with crayfish for numerous years at the Corn Creek refuge, while the dual invasion of crayfish and mosquitofish was associated with a rapid population decline of the largest Pahrump Poolfish refuge population at Spring Mountain Ranch.