SQMCI: A biotic index for freshwater macroinvertebrate coded‐abundance data

Abstract

A new freshwater macroinvertebrate‐based biotic index derived from the Quantitative Macroinvertebrate Community Index (QMCI) is proposed for use with coded‐abundance data collected from stony New Zealand streams using hand nets. The SQMCI (Semi‐Quantitative MCI) responds to changes in community dominance in a similar manner to the QMCI, but requires fewer replicate samples to achieve the same precision. In situations where macroinvertebrate densities are not required, the SQMCI provides a similar assessment to the QMCI with less than 40% of the effort, thus reducing the cost and/or improving the scientific defensibility of biomonitoring programmes. Variability of biotic indices must be known to enable detection of significant differences in water quality between streams, at different sites in the same stream, or between times at the same site. Best estimates of MCI and QMCI standard deviations have been updated, and newly derived for the SQMCI, for use in two statistical procedures for testing for significant differences between paired index values.