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Biotic indices based on community composition and calculated from sensitivity scores assigned to individual taxa are commonly used as indicators for ecological integrity of fluvial ecosystems. Macroinvertebrate indices can assess water quality but invertebrate community composition also responds to other environmental factors including stream bed disturbance. This study presents a biotic community index that assesses stream bed stability in stony riffles. This Macroinvertebrate Index of Bed Stability is calibrated on transport and entrainment of in situ-marked tracer stones in 46 streams in New Zealand’s North Island, representing a wide range of substrate stability. Scores were investigated for 67 common invertebrate taxa using Indicator Species Analysis based on taxa abundance at varying levels of substrate stability. The resulting site score, weighted by taxa abundance, improved a predictive model of bed …