Predator presence influences survival and behavior of translocated stream fish in ponds

Small artificial impoundments such as farm ponds have recently been recognized as potential habitat for threatened native fish species. However, factors influencing translocation or colonization success into these environments, including connectivity to stream networks and interactions with existing fish community, are largely unknown. In this study we conducted a controlled experiment to quantify the influence of piscivorous Largemouth Bass Micropterus salmoides on the survival of a translocated native minnow species that we used as a surrogate for federally endangered Topeka Shiner Notropis topeka. We translocated or released 100 Bluntnose Minnow Pimephales notatus into each replicate treatment ponds with and without Largemouth Bass in the summers of 2020 and 2021. Each minnow was implanted with a passive integrated transponder (PIT) tag. Translocated populations were monitored using stationary and mobile passive integrated transponder antennas and estimates of apparent survival and probability of detection for each pond were derived from open population mark-recapture models. Apparent survival was nearly two times higher in ponds without bass suggesting predation by bass leads to higher mortality. Additionally, probability of detection was nearly 10 times higher in ponds without bass, suggesting reduced movement of translocated minnows when bass were present. While the direct effect of mortality impacts translocated populations, the indirect effect of altered behavior may also be impactful on translocation success. These results confirm that Largemouth Bass can limit the success of translocated minnow species.