Fish assemblages in Great Basin streams: Disentangling environmental effects on community structure

ABSTRACT Objective Arid ecosystems are often undervalued for their ecological contributions, yet they frequently harbor endemic fish species that are critical for regional biodiversity and ecosystem function. The goal of this study was to identify key environmental drivers of fish community composition and to quantify their utility for describing the fish community structure in the Goose Lake basin—an endorheic valley in the Great Basin that is characterized by dynamic hydrology and susceptibility to changes in land use. Methods We used data from 35 sites that were distributed throughout the basin to analyze the relationship between fish community structure and environmental drivers. The data set included observed species abundances and habitat variables, categorized into hydrologic, topographic, fine-scale, and broadscale environmental drivers. We tested multiple hypotheses to evaluate different combinations of these environmental drivers in relation to fish composition. We predicted species abundances using the best fit model from a canonical correspondence analysis and explored their relationships with the environmental variables. We also used the best fit model to project site suitability for focal species groups based on their alignment with major environmental gradients. Results The best fit model from a canonical correspondance analysis identified significant environmental associations, with precipitation, woody debris, and the presence of pool habitat emerging as the main correlations with species abundance and distribution. Redband trout, Speckled Dace Rhinichthys osculus, and suckers were strongly associated with the main environmental gradients, whereas juvenile lamprey and Northern Roach (also known as Pit Roach) Hesperoleucus mitrulus showed weaker relationships with these patterns. The predicted species abundances and site suitability varied across the basin, with redband trout showing high affinity for cool, high-elevation forested streams, whereas minnows and suckers were more abundant in warmer sites at lower elevations with greater pool habitat. Conclusions These findings address critical data gaps in an understudied region and underscore the need to promote habitat heterogeneity to support a portfolio of resilient fish communities in this and other Great Basin aquatic ecosystems.