Small water, big potential: farm ponds and their potential for native fish conservation

Abstract

Small impoundments, particularly farm or agricultural ponds, are often overlooked as potential habitat for native species despite their ubiquity across many human altered landscapes. Farm ponds intermittently connect to streams during floods allowing species exchanges to and from these novel habitats. In 2014, a farm pond on Tallgrass Prairie National Preserve (TAPR) was found to contain federally endangered Topeka Shiner (Notropis topeka). This finding provided a unique opportunity to study how farm ponds can be used in native species conservation in conjunction with translocation. I used field and experimental studies to; (1) assess farm pond fish communities on a broad scale and investigate the factors structuring them, (2) quantify the impact of predator presence on the translocation success of a native minnow species, and (3) quantify the survival, movement, and reproduction of Topeka Shiner in select ponds and a stream on TAPR. I sampled 100 farm ponds across central Kansas in 2021 and more than half of sampled farm ponds contained stream fish to assess farm pond fish communities. Amphibians and crayfish dominated small, less permanent ponds, while larger ponds were dominated by stocked sportfish. Distribution modeling revealed a negative correlation between stocked fish and other community components and suggested that native stream fishes are most prevalent in intermediate size ponds with few or no sportfish. To look for mechanisms driving these correlations, I directly investigated interaction between sportfish and stream fish in farm ponds. I conducted a controlled experiment to quantify the influence of piscivorous Largemouth Bass (Micropterus salmoides) on the survival of translocated Bluntnose Minnow (Pimephales notatus). I translocated 1600 Bluntnose Minnow (Pimephales notatus) into replicate treatment ponds with and without Largemouth Bass. Each minnow was implanted with a passive integrated transponder (PIT) tag. Translocated populations were monitored using stationary and mobile PIT 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 that predation by bass could lead 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 heavily influence translocation success. These results suggest that Largemouth Bass could limit the success of translocated or naturally colonizing minnow species. Finally, I assessed the efficacy of using translocation as a conservation tool for the federally endangered Topeka Shiner. From 2019 to 2022, Topeka Shiner were captured from a naturally-colonized pond population on the TAPR and translocated to two nearby ponds and a nearby stream. A portion of all translocated Topeka Shiner were implanted with PIT tags, and some tagged individuals were returned to the source population. Overall apparent survival (mortality and emigration) estimates between six-week sampling intervals varied across ponds and the stream but were always greater than 0.5. We observed emigration and immigration in pond habitats during flooding and physically captures young-of-year Topeka Shiner in all habitats indicating successful reproduction. Translocation of wild individuals from stable populations to ponds, as in this study, is a viable and low-cost conservation strategy to both bolster populations and repatriate areas from which Topeka Shiner were extirpated. These findings may also have implications for other species of threatened and endangered minnows or amphibians that inhabit headwater streams across the Great Plains, particularly in more xeric regions and in light of climate change.