Finescale dace occurrence and abiotic and biotic covariates for the Belle Fourche River and Niobrara River basins

Aim The factors that set range limits for animal populations can inform
management plans aimed at maintaining regional biodiversity. We examine
abiotic and biotic drivers of the distribution of finescale dace
(Chrosomus neogaeus) in two Great Plains basins to identify limiting
factors for a threatened freshwater fish population at the edge of their
range. Location Great Plains, Nebraska, South Dakota, and Wyoming, USA
Methods We investigated abiotic and biotic factors influencing the
contemporary distribution of finescale dace in the Belle Fourche and
Niobrara River basins with Random Forests classification models using fish
surveys from multiple agencies spanning 2008 2019 and GIS-derived
environmental data. Results In both basins, finescale dace occurrence
exhibited a non-linear response to mean August water temperature. Abiotic
covariates, including streamflow, water temperature, and channel slope,
were important limiting factors in the final model fit with Belle Fourche
River basin surveys (n = 131). In contrast, a biotic covariate, native
minnow richness, was the most important predictor of finescale dace
occurrence in the Niobrara River basin model (n = 27). In the Niobrara
River native minnow richness was lower at sites with non-native northern
pike (Esox lucius). Main conclusions Basin-specific analyses revealed
context dependencies for species-environment relationships, which can
inform targeted restoration actions. Similar relationships between water
temperature and finescale dace occurrence across both basins suggests
summer thermal habitat as a regional limiting factor. The importance of
biotic interactions in the Niobrara River highlight an emergent threat
from invasive predators to a distinct assemblage of native prairie fishes.