Ecological status of Hout River Dam, Limpopo province, South Africa, using fish condition and health assessment index protocols: a preliminary investigation

Abstract

The ecological status of Hout River Dam was evaluated in 2011 by assessing fish health, based on condition factor (K), health assessment index (HAI) and inverted parasite index (IPI), which provided a simple and rapid means of establishing the health of fish. Surveys were conducted during summer, winter and spring 2011. To verify results, water quality was analysed during each survey. Clarias gariepinus, Oreochromis mossambicus and Cyprinus carpio were collected using conventional angling gear and gillnets. Mean K values of 0.6, 2.0 and 1.4, and HAI scores of 38, 41 and 35, were recorded for each species, respectively. The metrics that correlated best with fish health scores were haematocrit values and ecto- and endoparasite indices. Differences in K, HAI, and HAI using IPI determinations, were insignificant (p > 0.05) between species, while water contaminants, with the exception of ammonium (NH₄), nitrate (NO₃) and aluminium (Al) concentrations in summer, fell within the levels stipulated by the South African target water quality range guidelines for aquatic ecosystems. It was thus inferred that the dam was in a good ecological state.