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Fish Assemblage Patterns as a Tool to Aid Conservation in the Olifants River Catchment (East), South Africa
Citation:
RASHLEIGH, B., D. Hardwick, AND D. Roux. Fish Assemblage Patterns as a Tool to Aid Conservation in the Olifants River Catchment (East), South Africa. Water SA. Water Research Commission, PRETORIA, South Africa, 35(4):517-524, (2009).
Impact/Purpose:
Objectives were to identify patterns within the fish assemblages in the Olifants, to better understand the natural and anthropogenic influences on these fish assemblages, and to identify aspects that are important for conservation. This work should provide insight to appropriate conservation and management policies, and help to restore and improve biotic integrity in this system.
Description:
South Africa has committed to address freshwater conservation at the catchment scale, using a combination of landscape-level and species-level features as surrogates of freshwater biodiversity. Here we examined fishes in the Olifants catchment, where multiple anthropogenic pressures affect streams. We analyzed patterns in fish assemblage data for 87 sites, using data from the National River Health Programme and a series of landscape environmental variables. Multivariate ordination and cluster analysis identified six distinct assemblage types, which were separated by altitude and human influence, primarily dryland cropping and dams. Classification and regression tree analysis was performed for selected species and for species diversity. In the upper reaches of the catchment, a faunal shift occurred with land use change, from more sensitive species to more tolerant species. The fish assemblage of the middle section of the catchment was not unique, but it did support one species, C. pretoriae, that could be considered a focal species. The low elevation, high-yield section of the catchment supported the most species, however, diversity increased in association with dams, through the addition of flow-tolerant species, so diversity may not be an optimal conservation target for this system. Rather, a series of indicators will be necessary to track and measure conservation success in the Olifants catchment.
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Fish Assemblage Patterns as a Tool to Aid Conservation in the Olifants River Catchment (East), South Africa