Investigating the influence of hydrological phase on Baetidae and Simuliidae species composition in a South African non-perennial river: the Seekoei River
Ferreira, Ina S.
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All rivers should be monitored to detect changes and disturbances in order to be managed sustainably. Although non-perennial rivers are widespread and common in the semi-arid and arid areas of South Africa they have not been studied extensively. SASS 5 (South African Scoring System version 5) is the standard rapid bio-assessment method used to determine the present state of macroinvertebrates in South African rivers. The SASS 5 method was, however, developed for use in perennial rivers, and regardless of its inaccuracy in non-perennial rivers is still used in these rivers. This study tested the hypothesis that the SASS 5 biomonitoring method does not consider natural changes caused by the hydrology in non-perennial rivers and that family level identification is not accurate enough to reflect the changes in the state of the river. The Seekoei River, used as a case study, is an ephemeral (non-perennial) river, situated in the Northern Cape and is part of the Upper Orange Water Management Area. The autumn samples collected at two sites (EWR 3 and EWR 4; 2006 – 2010) in the Seekoei River during a WRC project (WRC research project K5/1587) were selected for the current study because of the ideal habitat and hydrology experienced at the sites. Two main hydrological phases were identified during the sampling period, i.e. FLOW phase and POOLS phase. Three years (2006, 2008, 2010) experienced the FLOW phase and two years (2007, 2009) the POOLS phase. Two macroinvertebrate families, Simuliidae and Baetidae, were used to determine the influence of species identification on the interpretation of biomonitoring data in non-perennial rivers. The results showed that species within the same family have certain flow and habitat preferences, which would not be detected using family-level data. This should be kept in mind when these rivers are managed. This study concluded that the information available from species-level analysis is important during the management of non-perennial rivers and therefore species-level data together with family-level data should be considered for use.