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Conservation of Tigerfish, Hydrocynus Vittatus, in the Kruger National Park with the Emphasis on Establishing the Suitability Of

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Conservation of Tigerfish, Hydrocynus Vittatus, in the Kruger National Park with the Emphasis on Establishing the Suitability Of 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 Report to the WATER RESEARCH COMMISSION by NJ Smit1, V Wepener1, W Vlok3, GM Wagenaar2 & JHJ van Vuren2 1North West University 2University of Johannesburg 3BioAssets CC WRC Report No. 1922/1/12 ISBN 978-1-4312-0358-1 JANUARY 2013 Obtainable from Water Research Commission Private Bag X03 Gezina, 0031 [email protected] or download from www.wrc.org.za DISCLAIMER This report has been reviewed by the Water Research Commission (WRC) and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the WRC, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. © WATER RESEARCH COMMISSION ii EXECUTIVE SUMMARY BACKGROUND Hydrocynus vittatus Castelnau, 1861, commonly known as tigerfish, is a flagship species widely distributed in the North Eastern region of South Africa, and are easily identified by the public. This species is actively targeted and utilised by angling and subsistence fishing communities and also used as indicator species by resource and water quality managers to transfer ecosystem related information to the public. Tigerfish therefore has a high ecological, economical and social value to South Africans. Unfortunately, they are lost through habitat changes caused by water extraction, pollution and obstructions like dams and weirs. Tigerfish depend greatly on the available natural habitats to breed, feed and function appropriately. A slight change in the environment may cause depletion of the overall population. Tigerfish are considered rare in South Africa and are classified as a protected species. Scientific studies of all aspects of tigerfish biology are therefore vitally important to understand what quality habitat is required for its successful survival. This information is necessary to development a conservation plan for tigerfish in South Africa. The ecological and economic importance and current conservation status of the tigerfish lead to the current project undertaken by researchers from the Centre for Aquatic Research (CAR) in the Department of Zoology, University of Johannesburg and Water Research Group (WRG), Unit for Environmental Sciences and Management, North West University. Historically tigerfish were prevalent in all 6 major rivers in the Kruger National Park (KNP) and areas on the western border of the Park. Recent surveys have shown that the distribution of this protected species is drastically reduced. The development of a management strategy to protect tigerfish within the Kruger National Park rivers is therefore of utmost importance. As a top predator tigerfish bio-magnifies pollutants and the risk that these pollutants pose are greater to them than to the lower trophic levels. A single study on metal levels in the Olifants River is the only information on levels of contamination in tigerfish. The levels of organic and inorganic substances together with the information on population structures and reproductive status will provide valuable insight into whether exposure to these contaminants has an influence on the general health of tigerfish populations in the KNP. This study addressed all the factors that might influence the health and conservation status of tigerfish. The upper catchments of all the rivers that run through the KNP are subjected to mining as well as intensive agricultural activities with high contamination potential. This tigerfish project was conducted on request from the KNP Scientific Services who identified the management of tigerfish within the borders of the KNP iii as a conservation priority. The study dealt with questions on the sufficiency of the current ecological water allocation for the Olifants River in terms of aquatic species requirements in the system as well as individual and population health. OBJECTIVES AND AIMS AIM 1 Determine the current distribution of tigerfish in the Olifants and Luvuvhu Rivers within the KNP. AIM 2 Determine the biological requirements of Kruger National Park tigerfish. AIM 3 Determine whether the environmental water allocation for the Olifants and Luvuvhu Rivers is sufficient to support a healthy tigerfish population. AIM 4 Determine the factors that might limit the current distribution of tigerfish in the Olifants River in the KNP, including water quality and habitat modification. AIM 5 A) Propose a management strategy for the conservation of tigerfish in the KNP with emphasis on mitigating measures to stimulate tigerfish populations to return to their original natural habitats. B) Validation and consolidation of the use of tigerfish as indicator species of quality and quantity related Threshold of Potential Concern (TPC) in the Olifants and Luvuvhu Rivers. METHODOLOGY Four sites were selected along the Olifants River as it flows through the KNP with the fifth site at the confluence of the Letaba and the Olifants River in the Olifants River Gorge. An additional site was selected in the Letaba River just before its confluence with the Olifants River. Four sites were selected along the Luvuvhu River as it flows through the KNP towards Mozambique. The first site was where the river enters the KNP opposite an informal rural settlement and the last site before the confluence of the Luvuvhu and the Limpopo Rivers. Water and sediment quality Physico-chemical water parameters were taken in situ at each sampling site in both rivers. Samples were frozen and transported to the laboratory for further analysis. After thawing samples suspended metal, chemical and turbidity analyses were done using standard techniques. High and low flow (HF, LF) surveys were done in 2009 (LF only), 2010 and 2011 (HF only). Sediment samples were analysed for the levels of inorganic and organic pollutants, percentage organic carbon and grain size. The Community Bureau of Reference iv (CBR) extraction procedures were used for the separation of metals. Certified reference materials (CRM) were used to test the analytical efficiency and for quality control. Pooled dried sediment samples from each site were analysed for organochlorine pesticides (OCPs) with a gas-chromatograph (GC) employing standard techniques. Quality assurance and quality control was achieved by using a corresponding standard. Habitat Different biotope diversities were evaluated in the current including instream and marginal vegetation, and GSM (gravel, sand, mud). A fish habitat assessment was conducted to describe the fish refuge potential at each of the sampling sites. Macro-invertebrates and Fishes The sampling of the Olifants and Luvuvhu Rivers was done over two consecutive LF seasons. The macro-invertebrate composition at all the sites on both the Olifants and Luvuvhu Rivers were determined and assessed. The Fish Response Assemblage Index (FRAI) was compiled. Standard techniques were employed in both cases. Sites were used that had been previously sampled and those that had a Reference Frequency of Occurrence (FROC). Representative habitat biotopes were sampled employing approved fish sampling techniques. Histopathology assessments were done to establish the health of selected fish species from both river systems. Flow-dependent habitat type preferences by fishes of the Olifants River were done using a spatial habitat modelling exercise, fish community structure assessment and a desktop evaluation of habitat preferences. The effects of altered flow dependent habitat types on fish communities were done with a flow-stress assessment. Fish communities sampled in the habitats were used to determine different community structures. Multivariate statistical procedures and Geographical Information Systems (GIS) modelling procedures were used to evaluate the habitat and flow preferences of the fish communities. Fish Health Assessment The condition factor was determined after sampling and the hepato-, gonado- and spleno- somatic indexes calculated for each species. Histopathology analyses were done on gill, liver, kidney and gonad samples. Otoliths were prepared for age determination. Bioaccumulation Levels of Cu, Mn, Pb, Cd and Hg in muscle tissue were determined with ICP-OES and ICP- MS using standard techniques for sample preparation and analysis. The DDT congeners – p,p’-DDE, o,p’-DDE, o,p’-DDD, p,p’-DDD, o,p’-DDT, o,p’ and p,p’-DDT (Sum ΣDDTs), hexachlorobenzene (HCB), α-, β-, γ and δ-hexachlorocyclohexane (HCH) isomers (Sum ΣHCHs), the chlordanes (ΣCHLs) – cis- and trans chlordane (cChl, tChl), its oxidised form, i.e. oxychlordane (OxC), and heptachlor (HC) and its break down products cis- and trans were also determined. v Biomarker responses A gram tigerfish liver and muscle were mixed with Hendrickson stabilising buffer, and stored in liquid nitrogen for biomarker analysis. The remaining portions of the axial muscle were frozen in for further analysis. Values were obtained for biomarkers of exposure and effect. Statistical analyses Data were analysed by one-way ANOVA, with sites as variables. Data were tested for normality and homogeneity of variance using Kolmogorov-Smirnoff and Levene’s tests, respectively. Post-hoc multiple comparisons between sites were made using the appropriate Scheffé (parametric) or Dunnette-T3 (non-parametric) test to determine significant differences (p<0.05). Univariate diversity indices were used to assess community structures, species richness and diversity.
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