Preliminary testing of the Integrated Habitat Assessment System (IHAS) for aquatic macroinvertebrates

Abstract

Preliminary testing of the Integrated Habitat Assessment System (IHAS), a widely-used aquatic macroinvertebrate habitat assessment method in South Africa, was undertaken. Based on the sensitivity of the South African Scoring System (SASS) to biotope availability and assuming that SASS Scores at minimally-impacted reference sites are the highest Scores attainable, one would expect to find a positive relationship between SASS Scores and IHAS scores at reference sites. The preliminary testing undertaken is based on the assumption that this relationship should be linear. For data obtained from reference sites in Mpumalanga and the Western Cape, non-parametric correlation analyses were undertaken between SASS4/5 Scores and IHAS scores, using Kendall's Rank-correlation Coefficient. Separate analyses were undertaken for different geomorphological zones and biotope groups. Results were generally unsatisfactory, with non-significant correlations (P > 0.05) for two-thirds of the data sets analysed. Performance of the IHAS varied between geomorphological zones and biotope groups, with best results obtained for the Foothill: Gravel-bed Zone in Mpumalanga, particularly with the stones-in-current biotope analysed separately. Further testing is required to confirm the relative performance in different bioregions/ecoregions, geomorphological zones and biotope groups.