Evaluation of two fish-based indices of biotic integrity for assessing coldwater stream health and habitat condition in Iowa's driftless area, USA.

Multiple fish-based indices of biotic integrity (FIBI) exist to estimate stream health using fish community structure. Yet, these metrics require different amounts of data and may result in different interpretations of stream health. We compared functionality of "low-metric" (5 metrics) and "metric-rich" (12 metrics) coldwater FIBIs for estimating stream health in 138 coldwater streams of northeastern Iowa, USA. Then, we investigated associations between FIBI scores and environmental factors at local and catchment scales using mixed effects linear regression. FIBI scores from both protocols were positively correlated (R² = 0.77); the majority of streams scored fair (n = 31, mean = 45; fair) using the metric-rich index but scored very poor using the low-metric index (n = 35, mean score = 25; poor). FIBI scores were higher (mean = good) when Brook Trout Salvelinus fontinalis were present with both indices. When Brook Trout were absent, scores were lower and less variable with the low-metric index (mean = 19.63; poor) compared to the metric-rich index (mean = 40.38; fair). Local habitat was more related to both FIBI scores than catchment-scale habitat: maximum daily stream temperature and bare bank severity index were negatively correlated with both FIBI scores whereas canopy coverage correlated positively with metric-rich FIBI scores. Brook Trout presence was indicative of coldwater stream health for both indices. Our results suggest the metric-rich FIBI index has improved ability to differentiate lower quality sites due to increased sensitivity. Our results can be used to improve stream health estimates and restoration prioritizations. [ABSTRACT FROM AUTHOR]