SQMCI - A BIOTIC INDEX FOR FRESH-WATER MACROINVERTEBRATE CODED ABUNDANCE DATA

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 stream s using hand nets. The SQMCI (Semi-Quantitative MCI) responds to chang es in community dominance in a similar manner to the QMCI, but require s fewer replicate samples to achieve the same precision. In situations where macroinvertebrate densities are not required, the SQMCI provide s a similar assessment to the QMCI with less than 40% of the effort, t hus 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 betwe en streams, at different sites in the same stream, or between times at the same site. Best estimates of MCI and QMCI standard deviations hav e been updated, and newly derived for the SQMCI, for use in two statis tical procedures for testing for significant differences between paire d index values.