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Conservation of tigerfish, hydrocynus vittatus, in the Kruger National Park with the emphasis on establishing the suitability of the water quantity and quality requirements for the Olifants and Luvuvhu rivers
Expanded Title:Tigerfish , now a protected species, were once prevalent in all 6 major rivers in the Kruger National Park and on its western border. Recent surveys have shown that their distribution has drastically declined. Tigerfish are now considered to be rare in South Africa and as of 2008 are classified as a protected species alongside great white sharks and the coelacanth. The Tigerfish has a high economic and social value to South Africans as the species is utilised by various angling and subsistence fishing communities in this part of the country. The fish also has an ecological value as an indicator species. Unfortunately, before scientists fully understand some of the biological attributes of this species, it is being lost at high rate due to water extraction, pollution and obstructions like dams and weirs. A management strategy is therefore required for the protection of this iconic fish within the Kruger National Park. The overall aim of this study was to examine the sufficiency of the current ecological water allocation for the Olifants River in terms of fish requirements in the system, as well as individual and population health. Ten sites covering the Olifants river, Letaba and Luvuvhu within the park were sampled for water/sediment quality, habitat biodiversity, fish, macro-invertebrates, fish-health, bioaccumulation and biomarkers tests. Various statistical methods were employed for intensive data analysis. Almost all the in-situ water quality parameters fell within the target water quality range (TWQR) for aquatic ecosystems. Macro-invertebrate abundance decreased downstream, and low numbers of fish species were recorded. Though fish bio-accumulated various pollutants, the fish health index proved they were healthy (tigerfish), with limited liver reaction to biomarkers. Tigerfish does respond to the presence of low levels of pollutants. Fortunately, their highly mobile nature enables them to avoid exposure to debilitating stressors. (Tigerfish may therefore not be an ideal indicator species for water quality). However, results from the flow assessment clearly show that Tigerfish have very specific flow and habitat requirements, making them an excellent indicator species of water quantity and flow. (Tigerfish was found to have a high preference for only two habitat types i.e. deep (>1200mm) and fast flowing (>0.8m/s) conditions .) (All fish species from the Olifants River have identifiable habitat preferences that can be applied to evaluate the effects of reduced flows.) Low flow discharges of approximately 17m3/s in the Olifants River may begin to show higher levels of stress in fish due to reductions in habitat diversity and abundances. Below a flow of 4.9m3/s the resulting reduction in flow dependent habitat types would become severe. Current threshold for the drought flows in the Olifants river may be too low, and a minimum of 5.0m3/s is recommended for the conservation management strategy, targeting tiger fish in particular. It is proposed that KNP produce a conservation strategy, using the products of this research, with catchment as a unit of management, so that tigerfish and others will be fairly protected.
Date Published:01/01/2013
Document Type:Research Report
Document Subjects:Ecosystem - Invertebrates
Document Format:Report
Document File Type:pdf
Research Report Type:Standard
WRC Report No:1922/1/13
ISBN No:978-1-4312-0358-1
Authors:Smit NJ; Wepener V; Vlok W; Wagenaar GM; Van Vuren JHJ
Project No:K5/1922
Organizations:North West University; University of Johannesburg; BioAssets CC
Document Size:12 423 KB
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