|Abstract or Summary
- The conservation of declining desert fish species requires the identification of relations between fish population dynamics and their environments. Dynamic occupancy modeling, an approach that requires less information than traditional mark-recapture studies, may help identify important factors affecting population processes and aid desert fish conservation and restoration efforts. I used dynamic multi-season occupancy models for two analyses (multi-state and multi-species) to evaluate the influence of patch-level characteristics (patch percent open water, average patch depth, patch area), grazing damage, species interactions, population differences, patch connectivity and environmental variation (seasonal precipitation and temperature) on the patch dynamics (colonization, persistence, reproduction) of two desert chub species found in Snake Valley, UT. My results indicate that there was the strongest evidence according to model weights that patch dynamics in this system were influenced by patch-level characteristics (patch percent open water and average patch depth), grazing damage, population differences, biotic interactions, and winter precipitation rather than landscape level features such as connectivity. I observed positive effects of patch percent open water and average patch
depth on least chub and Utah chub persistence. I also found that grazing damage increased their persistence at the medium damage level but decreased least chub and Utah chub colonization at the high grazing damage level. Least chub and Utah chub colonization varied between the two populations (study areas) with a higher probability of colonization at Bishop Springs than at Gandy Salt Marsh. In addition, I found some evidence that biotic interactions between least chub and Utah chub may be occurring in this system. Least chub were less likely to colonize patches previously occupied by Utah chub but surprisingly there was little evidence that these species interactions affected least chub persistence. Least chub reproduction increased with winter precipitation and was higher at Gandy Salt Marsh than Bishop Springs. The use of dynamic occupancy modeling in desert spring wetland complexes may provide a valuable tool for managers tasked with conserving at-risk desert fish species.