Staying alive: Post-translocation apparent survival of fishes in headwater springs following drought

Abstract

Objective Increasing fragmentation from constructed barriers, increased water use, and climate change limits the resiliency of stream fish metapopulations by reducing colonization. Management actions such as stocking or translocating fish may help contribute to the resilience of isolated habitats and increase redundancy of populations in intermittent stream networks. Our objective was to determine whether translocating fish into prairie headwater refuges could reestablish or supplement isolated populations. Methods We examined apparent survival and probability of detection of four native, small-bodied fishes that were translocated in 2022 and 2023 to prairie headwater refuges that were affected by a severe drought and experienced slow recovery of their fish assemblages. All the fish were marked with passive integrated transponder tags, allowing us to use a mark–recapture framework to track the fate of these fish. Results Apparent survival was predicted by an interaction between time and translocation site, indicating an important consideration of environmental factors. Approximately one-quarter of the fish remained at site A through the summer of both years, whereas estimates were near zero at site B in both years and mixed across years at site C. The decreases in apparent survival probabilities following flow events suggest that fish may be emigrating during these periods of reconnection. During the lower flow year, more fish remained at the headwater sites and young-of-year fish were captured during long-term sampling, suggesting that the translocated fish reproduced. Conclusions The success of translocation projects will depend on a variety of factors, including management goals, habitat, and hydrology, but the initially high survival reported in this study is encouraging. Difficulties with examining the movement of small fish during hydrologic events limited our conclusions about the relative contributions of mortality and emigration to apparent survival estimates. Despite low yearly apparent survival, we found evidence of reproduction from translocated fish, suggesting that the reestablishment of a viable population is possible.