Prof Cate Brown Pengarang Dr Nick Rivers-Moore Pengarang

Sources of fish in the ephemeral western iishana region of the Cuvelai– Etosha Basin in Angola and Namibia MHT Hipondoka1* , BCW van der Waal2, MH Ndeutapo3 and L Hango4 ABSTRACT The triangle between the Kavango and Kunene rivers is drained by the Cuvelai, an ephemeral and deltaic drainage system covering more than 100 000 km2. In good rainfall years, the area becomes populated by fish communities dominated by five species migrating southward towards the endorheic Etosha Pan, the basin’s terminal sump. When water dries up, fish subsequently die-off and their sudden appearance in rainy years has captivated scientists for decades. The current study was prompted by hitherto untapped indigenous knowledge through narratives of opportunistic fish harvesting of migrating fish at temporary connections between the Kunene River and the CuvelaiEtosha Basin. A reconnaissance fish survey in 2017 was complemented by digital satellite images and elevation data analyses. Results support the presence of at least three major ephemeral fish migration routes. The dominant fish genera migrating upstream in Kunene tributaries comprise Enteromius, Oreochromis and Clarias, all eurytopic and known to undertake upstream, lateral and downstream migrations on floodplains. Although other notable fish refugia in the Cuvelai–Etosha Basin are yet to be identified, there is a necessity for the protection and management of these migration routes in tandem with studies on the nature and extent of this inter-basin fish migration under climate change and variability. Keywords: Clarias, Enteromius, Etosha Pan, fish migration, indistinct water divide, Kunene River, Oreochromis Relationships of water temperature and aquatic macroinvertebrate community structure with non-native riparian plant densities in the southern Cape, South Africa NA Rivers-Moore1* , HF Dallas2 , FC de Moor3 and J Barendse4,5 ABSTRACT Non-native vegetation in the riparian zone impacts on water temperatures, flow patterns, degree of shading, channel modification, and changes to natural sediment loads. Freshwater ecosystems in the Garden Route Initiative planning domain are of particular conservation value, because of the rich Gondwanaland relict aquatic macroinvertebrate fauna found in the rivers there, which are vulnerable to thermal changes. Data were collected during 2013 and 2014 at 19 sites on seven river systems between George and Knysna in the southern Cape, South Africa. These included 12 months of hourly water temperatures at all sites, and quantitative sampling of aquatic macroinvertebrates at ten sites. Each site was characterised in terms of water quality (pH, conductivity and turbidity) and general characteristics, including impacts such as density of non-native riparian trees. At the family level, aquatic macroinvertebrate= communities showed variation between sites and seasons. Differences were more pronounced on the basis of natural land cover type (fynbos versus indigenous forest) than densities of non-native invasive riparian vegetation. Conservation of these river systems will depend on maintaining a mosaic of natural vegetation types. Keywords: Flow variability, fynbos, geology, water quality, water temperature Triggers of phytoplankton bloom dynamics in permanently eutrophic waters of a South African estuary DA Lemley1*, JB Adams1 and NA Strydom2 ABSTRACT The permanently eutrophic Sundays Estuary experiences recurrent harmful algal blooms (HABs) of Heterosigma akashiwo (Raphidophyceae). This study aimed to identify the environmental variables shaping phytoplankton community composition and succession patterns during a typical spring/summer harmful algal bloom (HAB) period. Monitoring of abiotic and phytoplankton variables was undertaken over the period of a month in 2016. Surface water salinity corresponding to mesohaline conditions (9 to 12) was a prerequisite for site selection. During the study, two HABs (>550 µg Chl a l−1) of H. akashiwo occurred, each lasting for approximately a week in duration. Analyses highlighted nutrient depletion (i.e. nitrate and phosphate concentrations) as the key constraint on bloom duration. When the density of H. akashiwo decreased, the community composition became more diverse with species belonging to Bacillariophyceae and Dinophyceae becoming more abundant; albeit to a lesser degree (<180 µg Chl a l−1). Dissolved oxygen shifted from super-saturated conditions (>14 mg l−1) during peak HAB conditions, to instances of bottom water oxygen depletion (2–4 mg l−1) during the decay phase. These findings highlight the potential severity of transforming a catchment from natural to one that is highly regulated by agricultural practices, while also emphasising the need for management intervention. Keywords: Bottom-up controls; community succession; eutrophication; Heterosigma akashiwo; hypoxia Concentrations and ecological risks of metals in surface sediments of some coastal creeks in the Niger Delta, Nigeria ABSTRACT CMA Iwegbue1*, OV Beecroft1, JE Ogala2, FE Egobueze3, GO Tesi1, GE Nwajei1 and BS Martincigh4 The concentrations of nine metals were measured by atomic absorption spectrophotometry in surface sediments of three coastal creeks, namely, the Ifie, Egbokodo and Ubeji creeks, in the Niger Delta of Nigeria, from August 2012 to January 2013. The aim of the study was to provide information on the spatial and seasonal distribution patterns, degree of contamination, and ecological risks of metals in these sediments. The mean concentrations of the nine metals in these creek sediments ranged from 0.30 to 3.20 mg kg−1 Cd; 10.7 to 24.7 mg kg−1 Pb, 125 to 466 mg kg−1 Cr; 3.1.10 to 14.9 mg kg−1 Cu; 4.7 to 14.3 mg kg−1 Co; 61.1 to 115 mg kg−1 Ni; 106 to 183 mg kg−1 Mn; 52.0 to 170 mg kg−1 Zn and 5 469 to 20 639 mg kg−1 Fe. In general, the metal concentrations were higher in the dry season than the wet season, except for Cr. The concentrations of Cd, Cr, Ni and Zn were above their regulatory control limits in sediment as specified by the Nigerian Regulatory Authority and Cd was identified as the main ecological risk factor. The enrichment factors for the studied metals followed the order: Cd > Cr > Ni > Zn > Pb > Co > Mn > Cu. The average multiple pollution index values indicated that these sediments were severely polluted with significant inputs from Cd, Ni and Cr. Keywords: Contamination factors, distribution patterns, enrichment factors, pollution index, seasonal variations, soil quality Occurrence and distribution of organochlorine pesticide residue levels in water, sediment and aquatic weeds in the Nyando River catchment, Lake Victoria, Kenya DA Abong’o*, SO Wandiga and IO Jumba ABSTRACT Samples of water, sediments and aquatic weeds were collected from 26 sites in the Nyando River catchment of the Lake Victoria basin in 2005–2006. The objective was to investigate levels of organochlorine pesticides that have either been banned or are restricted for use in Kenya. The pesticides investigated were lindane, aldrin, endosulfan, endrin, dieldrin, DDT, heptachlor and methoxychlor. These pesticides had previously found wide applications in public health and agriculture in Kenya for control of disease vectors and crop pests respectively. Results showed that mean concentrations were highest for methoxychlor (8.817 ± 0.020 µg l−1) in water, sediments (92.893 ± 3.039 µg kg−1), and weeds (39.641 ± 3.045 µg kg−1), the weeds also tended to accumulate aldrin (15.519 ± 3.756 µg kg−1). The results show that the pesticides are still in use and are detected in the catchment. Stringent management and public awareness measures are required to enforce the ban on the organochlorine pesticides in order to safeguard the environment and ecosystems of Lake Victoria. Keywords: Agrochemicals, environmental pollution, farming, Winam Gulf Health and chemical burdens of fish species from polluted and hypereutrophic freshwater ecosystems in South Africa GM Wagenaar1* and IEJ Barnhoorn2 ABSTRACT Three aquatic ecosystems in South Africa, the Hartbeespoort, Klipvoor and Bospoort Dams, are classified as hyper-eutrophic, because of high nutrient loads and chemical pollution. Water and two fish species, Clarias gariepinus and Cyprinus carpio, were collected from these dams to assess the impact of eutrophication and chemical pollutants on their health status. Water and muscle samples were analysed for organic and inorganic chemicals. Condition factor was determined and a necropsy performed to note any macroscopic abnormalities. A histology-based fish health assessment was done on the liver, kidney, gills and gonads. A number of fish from the three dams exhibited livers with fatty change and focal discoloration, skin lesions and parasites within the visceral cavity. The prevalence and severity of histopathology in the liver resulted in higher liver index values than the index values for kidneys and gills. Aluminium, silicon and chromium were detected in the water and muscle tissue. The DDT metabolite p,p'-DDE was present in both species, as well as in fish from the reference site, Marico-Bosveld Dam. Only C. gariepinus from Hartbeespoort Dam had p,p'-DDD levels higher than 5 µg g−1 per edible portion. Water from hyper-eutrophic dams adversely affects the health of freshwater fish. Keywords: Bioaccumulation, eutrophication, fish health, histopathology, histology, metals, pesticides Biomarkers of toxicity in Clarias gariepinus exposed to sublethal concentrations of polycyclic aromatic hydrocarbons TO Sogbanmu1* , AO Osibona2, OA Oguntunde3 and AA Otitoloju1 ABSTRACT Physiological, biochemical and histological indices in Clarias gariepinus broodstock, and teratogenic indices in embryos exposed to sublethal concentrations of naphthalene, phenanthrene and pyrene were investigated in 2014 using a static-renewal bioassay protocol. Phenanthrene (1.41 mg l−1) was the most toxic, followed by pyrene (1.53 mg l−1) and naphthalene (7.21 mg l−1), based on 96 h LC50 values. Hepatosomatic indices were significantly higher in naphthalene- and pyrene-treated males compared with solvent controls, whereas fecundity in females was significantly lower by factors of 2.4 (naphthalene), 2.8 (phenanthrene) and 2.4 (pyrene), compared with controls. Catalase levels were lower in female phenanthrene-treated fish compared with controls. Histological alterations observed in PAH-treated fish include oedema, inflammatory cells, epithelial lifting and hyperplasia in the gills, vacuolation, haemosiderin pigments and sinusoidal congestion in the liver, and degenerated zona radiata in the ovary. Teratogenic effects were not observed, as evidenced by the lack of histological alterations in embryos spawned from pre-exposed broodstock. Sex-specific responses and the utility of biomarkers at cellular and individual levels of organisation are therefore demonstrated for holistic evaluations of polycyclic aromatic hydrocarbons in ecotoxicological studies. Keywords: African sharptooth catfish, biochemical indices, biological responses, histological alterations, naphthalene, phenanthrene, physiological indices, pyrene Acute toxicity effects of ibuprofen on behaviour and haematological parameters of African catfish Clarias gariepinus (Burchell, 1822) EO Ogueji1*, CD Nwani2, SC Iheanacho1, CE Mbah3, CO Okeke4, A Yaji5 ABSTRACT Indiscriminate discharge of pharmaceutical waste into the aquatic ecosystem may pose serious health challenges to aquatic biota. The effect of acute exposure to ibuprofen was evaluated using changes in behaviour and haematological parameters under static bio-assay method in Clarias gariepinus. Test specimens were exposed to acute concentrations of ibuprofen (0.28, 0.33, 0.38, 0.43 and 0.48 mg l−1) for 24, 48, 72 and 96 h durations respectively. Behavioural and phenotypic changes were observed in surviving fish. There were significant (p < 0.05) concentration and duration-dependent increases in erythrocyte (RBC), haemoglobin (Hb), pack cell volume (PCV) and leukocytes (WBC) in treated fish compared to the control. Insignificant decreases (p > 0.05) in mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) were observed in treated fish compared to the control. Ibuprofen elicited dose and durationdependent decrease in neutrophil counts with the decreases being significant (p < 0.05) in the higher doses of 0.43 and 0.48 mg l−1. Ibuprofen did not elicit any significant changes in monocytes, basophils and eosinophils. Changes observed in this study showed that ibuprofen negatively affected the health of the fish and we recommend that discharge of ibuprofen into the aquatic environment should be monitored and controlled. Keywords: aquatic pollution, freshwater fish, haematology, pharmaceuticals First report on OH-PAHs in South African Clarias gariepinus bile from an urban impacted system W Pheiffer1*, N Bortey-Sam2, Y Ikenaka1,2, SMM Nakayama2, H Mizukawa3, M Ishizuka2, NJ Smit1 and R Pieters1 ABSTRACT The concentrations of selected hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) were determined in the bile of the African sharptooth catfish Clarias gariepinus from impoundments in the urban impacted Klip River system in Soweto, South Africa. Fish were sampled from three impoundments (Lenasia, Fleurhof, and Orlando dams) during the early high-flow season (September/October) of 2013. Biliary OH-PAHs were analysed using a high-pressure liquid chromatograph coupled to a tandem mass spectrometer (HPLC-MS/MS). Seven of the thirteen targeted metabolites were present in the fish of Soweto. The ΣOH-PAHs ranged between 0.1 and 1 876 ng ml−1, with greatest ΣOH-PAH mean at Orlando (947 ng ml−1) followed by Fleurhof (371 ng ml−1). The most dominant metabolite in the sampling area was 2–,3–OH fluorene, ranging between not detected and 1 429 ng ml−1, with the greatest mean at Orlando (709 ng ml−1). PAH metabolites quantified in C. gariepinus most likely originated from the sediments. The hepatosomatic index of the C. gariepinus increased proportionally with the biliary OH-PAH concentrations. To the authors’ knowledge this data on biliary OH-PAH for fish is the first for South Africa. Keywords: Freshwater toxicology, Klip River, sharptooth catfish, Soweto Preliminary evaluation of non-native rainbow trout (Oncorhynchus mykiss) impact on the Cederberg ghost frog (Heleophryne depressa) in South Africa’s Cape Fold Ecoregion S Avidon1, JM Shelton1,2,3* , SM Marr3,4,5 , TA Bellingan5,6 , KJ Esler1,7 and OLF Weyl3,4,5 ABSTRACT We evaluated the impact of non-native rainbow trout Oncorhynchus mykiss on a population of endemic Cedarberg ghost frog Heleophryne depressa in the upper Krom River (Olifants-Doring River Catchment, Cape Fold Ecoregion). We compared H. depressa abundance (using kick-sampling and underwater video analysis) and environmental conditions between sites above and below a waterfall that marks the upper distribution limit of O. mykiss. Heleophryne depressa abundance was significantly greater above the waterfall than that below it, and, because there was no significant difference in measured environmental variables, O. mykiss presence is identified as the most likely explanation for the observed decrease in H. depressa abundance. Keywords: Amphibian, endemic species, freshwater fish, kick-sampling, Olifants-Doring River Catchment, underwater video analysis, waterfall barrier Possible influences of a macroalgal bloom in eelgrass beds on fish assemblages in the lower Knysna Estuary, South Africa M Pollard1,3*, AK Whitfield2 and AN Hodgson3 ABSTRACT The occurrence of a macroalgal bloom at eelgrass (Zostera capensis) sampling sites in the summer of 2014/2015 provided an opportunity to use underwater video cameras to monitor the possible effects of environmental change on fish diversity and abundance in the lower reaches of the Knysna Estuary. A General Linear Model (GLM) showed that there was a significant difference in the abundance of fish before and after an invasion of the sampling sites by the macroalga Ulva lactuca. The eelgrass bed fish abundance was more affected by the macroalgal bloom than the bare substratum fish abundance, with the Ulva impacting negatively on the relative abundance of Mugilidae in the former habitat. The hypothesis that macroalgal invasions have a negative effect on fish diversity and abundance is therefore supported by this preliminary study. Keywords: Mugilidae, Sparidae, Ulva lactuca, underwater video, Zostera capensis