The seasonal haematology of the Small-Mouth Yellowfish (Barbus holubi)

Hematological parameters in small-mouth yellowflsh (Barbia holubi) have been examined from February to November. Seasonal variations were observed in several of the parameters studied. Sexual differences were slight and no significant changes in haematology could be related to breeding season. The results are discussed in relation to other published observations

Determination of sediment quality in the Nyl River system, Limpopo Province, South Africa

The importance of wetland management and conservation is becoming more and more prevalent in the world today. It is thus important to determine baseline contamination values for wetlands to assist in making informed management decisions. Sediment from the Nyl River flood plain in the dry Limpopo Province was analysed using sequential extraction and ICP-MS to determine baseline metal concentrations, and bioavailability thereof. Eight heavy metal (Cu, Cd, Cr, Al, As, Zn, Mn, Pb) concentrations were determined and compared to sediment quality guideline values to assess sediment quality. Fractionation of the elements was also noted to assess the bioavailability of the metals. The results indicated that the sediment is of a fair quality in comparison to the sediment quality guideline values. They also indicate that the metals will only become available in the presence of strong reducing agents as most of the metal concentrations were recorded in the 4th and 5th fractions obtained from the Tessier sequential extraction of the sediment samples. The study concluded that the sediment is of a fair quality and that it poses little potential threat to the system.Keywords: sequential extraction, Nylsvley, wetlands, sediment quality, metal

Determination of sediment quality in the Nyl River system, Limpopo Province, South Africa

The importance of wetland management and conservation is becoming more and more prevalent in the world today. It is thus important to determine baseline contamination values for wetlands to assist in making informed management decisions. Sediment from the Nyl River flood plain in the dry Limpopo Province was analysed using sequential extraction and ICP-MS to determine baseline metal concentrations, and bioavailability thereof. Eight heavy metal (Cu, Cd, Cr, Al, As, Zn, Mn, Pb) concentrations were determined and compared to sediment quality guideline values to assess sediment quality. Fractionation of the elements was also noted to assess the bioavailability of the metals. The results indicated that the sediment is of a fair quality in comparison to the sediment quality guideline values. They also indicate that the metals will only become available in the presence of strong reducing agents as most of the metal concentrations were recorded in the 4th and 5th fractions obtained from the Tessier sequential extraction of the sediment samples. The study concluded that the sediment is of a fair quality and that it poses little potential threat to the system

Sublethal effects of manganese on the carbohydrate metabolism of Oreochromis mossambicus after acute and chronic exposure

Carbohydrate metabolism variables of Oreochromis mossambicuswere investigated after acute and chronic sublethal manganese exposure. The sublethal concentrations were determined from the LC50 value of manganese. After the exposures, the fish were carefully netted and blood was drawn from the caudal aorta. The differences in the values of carbohydrate metabolism variables of exposed fish were measured against control values and statistically analysed to prove statistically significant differences in variable values, caused by the metal pollutant (P < 0.05). The results obtained showed changes in the carbohydrate metabolism variables (glucose, lactate, glucose-6-phosphate dehydrogenase and pyruvate kinase concentrations). These alterations are produced as a result of increased levels of Cortisol and catecholamines, as well as hypoxic conditions. The latter induce hyperglycemia and increased lactate levels. Hypoxia may be a result of the damaging effect of manganese on the gills after exposure. The enzymes involved in the carbohydrate metabolism are sensitive to metal exposure and therefore enzyme concentrations fluctuated after the exposure to manganese. Enzyme function plays an important role in the catalysing of chemical reactions in an organism and the disturbance thereof could lead to death. Fish enzyme levels are therefore important biomarkers in the event of metal pollution in a water source

Bioaccumulation of chromium and nickel in the tissues of Barbus marequensis A. Smith, 1841 from the Lower Olifants River, Mpumalanga

Bioaccumulation of chromium and nickel in selected tissues and organs of the freshwater fish Barbus marequensis was investigated. According to the monthly data, the blood accumulated the highest amount of chromium, followed by the bile and vertebrae, while the skin accumulated the lowest amount. Nickel mainly accumulated in the blood, followed by the vertebrae and gills, while the lowest nickel concentrations occurred in the fat tissue. Although significant differences (p ≤ 0,05) between localities were detected, no definite trend as to where the highest bioaccumulation had occurred could be established. The levels in the tissues and organs of B. marequensis suggested no serious chromium or nickel pollution in the study area

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

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 iv 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

The occurrence of large branchiopod crustaceans in perennial pans: A research note

Pans are isolated, shallow depressions that are endorheic in nature. Because of the natural hydrological functioning of pans, these systems are usually restricted to arid regions and complete desiccation occurs seasonally. In the eastern provinces of South Africa many pans are perennial in nature often remaining inundated for several years. A study of the aquatic invertebrate community structure of selected perennial pans indicated that when these systems undergo complete desiccation, the communities are comparable to the communities of ephemeral ecosystems. During these periods the community displays normal succession patterns with branchiopod crustacean  dominating the community structure a few weeks after inundation. These perennial ecosystems are comparable to similar habitats around the world but are under  increasing threat due to an increase in mining and agricultural activities within the study area.Key words: hydroperiod, large branchiopods, pans

The female reproductive cycle of the european common carp, Cyprinus carpio, at a Transvaal fish farm: Gonadal morphometric development

The annual reproductive cycle of Cyprinus carpio was investigated using morphometric parameters of the body and gonads, including fecundity estimations, gonadosomatic indexes as well as histological evaluation and classification of oocyte developmental stages. It was concluded the C. carpio has an extended spawning season under temperate conditions, from early spring (September) to late summer (February). Results further suggest that by manipulating temperature and daylight period during late winter (August) it would be possible to induce spawning during this period

Health of sharptooth catfish Clarias gariepinus in Pongolapoort Dam, South Africa: a comprehensive study

A histology-based fish health assessment protocol was used in 2009–2010 to assess the health status of Clarias gariepinus from Pongolapoort Dam, South Africa. Nineteen fish were collected by angling. The histology of liver, kidney, gills and testes or ovaries was semi-quantitatively assessed and compared to that of fish from a reference site in the Okavango Panhandle, Botswana. Necropsy observations indicated that C. gariepinus from Pongolapoort Dam were in poorer condition than those from the Okavango Panhandle. Microscopic analysis showed that the mean liver index (IL), gill index (IG), testis index (IT) and ovary index (IO) were higher, although not statistically significant, in fish from the Okavango Panhandle. The difference in the results between the necropsy-based observations and semi-quantitative histological results was due to the external abnormalities detected in the necropsy analysis, including parasites and skin lesions, not expressing as changes to cell and tissue structure. According to the parameters measured, C. gariepinus from Pongolapoort Dam were in a healthy state.http://www.ajol.info/index.php/aja

Lethal copper concentration levels for <i>Clarias gariepinus</i> (Burchell, 1822) @ a preliminary study

Lethal copper concentrations were determined for both adult and juvenile Clarias gariepinus at representative mean summer and winter temperatures. Fish were exposed to copper for 96 hours in an experimental system and mortalities monitored. Toxicity curves of percentage mortality versus actual copper concentration were drawn, and the LC50 calculated for winter and summer temperatures. The lethal copper concentrations, expressed as LC50, found in laboratory exposures, ranged for adults from 1,29 mg/1 during summer to 1,38 mg/1 in winter. These values are considerably higher than the levels of copper in the water of the Olifants River in the Kruger National Park during summer (0,055 @ 0,016 mg/1) and winter (0,085 @ 0,032 mg/1). The derived LC50 values predict the level of copper which should be prevented at all cost. The fish in the Olifants River are already exposed to sublethal concentrations (40 of LC50) of copper. The results can be used as an indication of what the safe concentrations of copper should be