Temporal Change in Fish Communities and Modification of the Index of Biotic Integrity for the James River of the Dakotas

Over the past 25 years, the James River has experience records in minimum and maximum discharge. Fluctuations in flow rates over a wet I dry hydrologic cycle result in habitat instability, leading to an unstable, yet persistent, fish community. My first objective was to examine persistence of the James River fish community over an 11 and 25-year period. My second objective was to assess the relative abundance of fish among four major habitats (snag, low head dam. rocky bottom. and simple) following a wet I dry hydrologic cycle. Comparison of species richness data for the entire James River basin in North and South Dakota revealed 41 species being collected during 1975 while 50 species were collected from 1998 to 2000. In South Dakota there were 29 species after several dry years (1989/90) whereas 35 species were collected after several wet years (2000). Overall, 93% of the fish species collected during 1975 have persisted to the present. Density (number of fish In/± 1 SE) in four macrohabitats was: low head dams (dry = 1.23 ± 0.35. wet = 0.32 + 0.08). snags (dry = 0.56 ± 0.09, wet = 0.14 ± 0.02). rocky bottom (dry = 0.53 ± 0.11. wet = 0.13 ± 0.03). and simple (dry = 0.40 ± 0.07. wet = 0.11 ± 0.02). While the cycling hydroperiod influences the relative abundance of fish between wet and dry years. most species within the basin have persisted over the past 25 years, as species native to this system have adapted to inhabit the harsh physiochemical environment of prairie streams. Assessing fish community health in prairie streams using the index of biotic integrity (IBI) requires robust metrics to account for natural variability that characterizes these lotic svstems. Twentv-two metrics were tested and used to modify an IBI to assess the biological health of five regions within the basin (lower river. middle river. Upper river. SD tributaries. ND tributaries). Fish community datasets from several studies in both ND and SD covered both high and low discharge years over 11 years. Scoring criteria were set for 22 metrics in five regions of the James River basin. Scatter plots, Pearson correlation coefficient. Kendall\u27s tau, and coefficient of variation were used to reduce redundancy among metrics and assess metric responses to various levels of biotic integrity. The IBI was useful for assessing sites within the South Dakota portion of the basin. Most site scores ranged in quality from good to poor. Non-point source pollution appeared to be the major factor influencing fish community integrity. Sites characterized by heavy sedimentation and little to no riparian zone often received the lowest scores. Low species richness resulted in poor metric performance for the North Dakota portion of the basin. Further testing may identify other measures that respond to a gradient of anthropogenic disturbance