A survey of the fish fauna of Transkei estuaries Part Four: The Mntafufu and Mzamba River estuaries

The Mntafufu and Mzamba Rivers have small catchment areas (178 and 505 km2, respectively) in the forested coastal belt of Transkei and have relatively small estuaries (5 and 2 km long, respectively). Although the annual rainfall is in excess of 1000 mm in this area, the mean annual runoff was less than 70 Mm3 in both cases. Serious floods were not observed during the survey period, while turbidity and sediment loads were usually very low. Salinities were usually high (x̄ = 30,0-38,0‰) in the bottom water and temperatures in the upper reaches were usually higher than in the lower reaches. The species composition, and seasonal and spatial abundance of the fish fauna of the two estuaries were determined by means of gill nets. A total of 1043 fish (385,8 kg) representing 42 species were caught in the Mntafufu estuary. The orangemouth glassnose Thryssa vitrirostris and V. cunnesius were the most abundant fish in the estuary. Numerically 42% of the catch (46% gravimetrically) belonged to the family Mugilidae (11 species) of which Mugil cephalus, Valamugil buchanani and V. cunnesius were the most important. A total of 389 fish (241,1 kg) were caught in the Mzamba estuary. Twenty-five species were obtained with Hilsa kelee dominating numerically. Seven species of mullet contributed 38,3% of the numbers or 54,2% of the fish biomass. The diamond mullet (Liza alata) and the flathead mullet (Mugil cephalus) were the most abundant in terms of biomass. The highest catches in the two estuaries were taken in the lower reaches. Mean number and biomass of fish taken per net was 20,5 fish and 7,2 kg, and 16,2 fish and 10,1 kg in the Mntafufu and Mzamba estuaries, respectively

Bioacciimulation of copper in the tissues of Potamonautes warreni (Calman) (Crustacea, Decapoda, Branchiura), from industrial, mine and sewage-polluted freshwater ecosystems

The copper concentration detected in the water and sediments of the Natalspruit River, Bronkhorstspruit River and Nooitgedacht Dam exceeded certain stated limits for the protection of aquatic life. Despite considerable individual variation, the general ranking of copper concentrations in the various tissues was carapace < muscle < gonads < midgut gland < gills. Seasonal variation was detected in the bioaccumulation of copper in crabs sampled from the Natalspruit River. However, this phenomenon did not occur in crabs from the other two water bodies. A significant increase in copper concentrations was detected with a decrease in size, indicating that the size of the crabs is an important influencing factor in the bioaccumulation of copper. It was also found that more copper accumulated in the ovary than in the testis per unit weight. The bioaccumulation factors (BF) calculated for the different tissues with respect to the water were highest in the gills and midgut gland (785,00 – 1257,50 and 432,00 – 1340,00, respectively). The BF with respect to the copper concentration in the sediments was comparatively low for all the tissues (<0,10 – 2,74). It appears that P. warreni is able to regulate the copper concentrations in its various tissues and is therefore not a suitable indicator of the presence of copper in the aquatic environment

The qualitative and quantitative description of growth and condition of silver kob, A. inodorus

Thesis (MscAgric (Animal Sciences))--University of Stellenbosch, 2006.The development of basic husbandry techniques and determining basic performance parameters are among the first steps towards culturing a new species. Silver kob, Argyrosomus inodorus, is a large Sciaenid and endemic to South Africa and Namibia and has been selected as a candidate aquaculture species. However, the proposed culture raises many questions, with two of them being the adaptability to captive conditions and product quality in the captive raised fish. To address these, trials were set up with eighty-three silver kob, divided into three ponds and fed three different diets. The effects of the diet on performance and quality were determined over a nine month trial period. The fish fed the pilchard diet adapted faster to the captive conditions than the fish fed the artificial diets. The growth of these fish were also markedly better than that of the fish fed the artificial diets, although after the adaptation period, the growth rate of the fish fed the artificial diets surpassed that of the fish fed the pilchards. Fifteen fish, five from each treatment were sacrificed and compared on a chemical and sensory level to wild-caught fish (control, n=6). Differences (p≤0.05) were noted in the total lipid content and fatty acid composition between the fish fed the different diets and the control. Sensory analysis revealed that the fish fed pilchards differed (p≤0.05) from the other groups by having an undesirable odour and flavour. The body partitioning and the proximate chemical composition of silver kob were determined. The length-weight relationship for silver kob raised in captivity was determined and a b-value of 3.32 was obtained, which indicates allometric growth with the fish becoming more rotund as their length increases. The results of these trials indicates that silver kob, A. inodorus adapts in captive conditions. The final product also compares favourably to wild-caught fish. The use of digital image analysis as a method of determining fish condition was also assessed with promising results for future application in research and production systems

Some observations on the narcotizing ability of electric currents on the common carp Cyprinus carpio

Some effects of alternating current electronarcosis and of rectified current electronarcosis on C. carpio were investigated. In all instances recovery from narcosis was accompanied by convulsive spasms. Haemorrhaging of the gills was also observed to occur. Carp do not appear to be suitable candidates for electronarcosis.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.lmchunu2014mn201

Investigations into the effects of concentration and duration of exposure to formalin and malachite green on the survival of the larvae and juveniles of the common carp Cyprinus carpio L. and the sharptooth catfish Clarias gariepinus (Burchell)

Prophylactic dip treatments using formalin and malachite green were applied to 4-day old larvae and 12- and 20-day old juveniles of the European common carp, Cyprinus carpio and the African sharptooth catfish, Clarias gariepinus. Treatments consisted of 100mg/l malachite green for exposure periods of 10, 30 or 90s and 200mg/l formalin, administered for 30, 60 or 90 min. Larvae and juveniles of C. gariepinus could be treated with 100mg/l malachite green for 10s, or with 200mg/l formalin for 30min, with minimum mortalities. Both chemicals affected the survival of the C. gariepinus juveniles, especially the 90 min exposure to formalin. Juveniles of both species were extremely sensitive to 100mg/l malachite green concentrations.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.University of the North. Rand Afrikaans University.mn201

The use of electronarcosis as anaesthetic in the cichlid, Oreochromis mossambicus (Peters). I. General experimental procedures and the role of fish length on the narcotizing effects of electric currents

Procedures to narcotize fish by means of alternating or direct electrical currents are described and a method of evaluating the narcotic effects on fish of electrical currents is detailed. The role of fish length on the narcotizing potential of electrical currents was investigated. The results indicate that there is a positive correlation between fish length and the duration of narcosis.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.lmchunu2014mn201

The use of electronarcosis as anaesthetic in the cichlid, Oreochromis mossambicus (Peters). II. The effects of changing physical and electrical parameters on the narcotizing ability of alternating current

The effects of wave form, voltage, frequency and current as well as application time on the narcotizing ability of alternating current were investigated. A 60 Vrms, 50 Hz sine wave current applied for 30 s produced narcosis of sufficient duration to enable handling and blood sampling. A triangle wave form was inferior in narcotizing ability to both sine wave and square wave forms. Duration of narcosis increased with increasing water conductivity but was reduced by increasing water temperatures.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.lmchunu2014mn201

Treatment of Cyprinus carpio L. and Clarias gariepinus (Burchell) embryos with formalin and malachite green : effect of concentration and length of treatment on their survival

Malachite green and formalin were investigated as prophylactic dip treatments for developing embryos of Cyprinus carpio and Clarias gariepinus. Based on the findings, recommendations are made on the respective concentrations to be used and exposure periods to be followed for both formalin and malachite green for both fish species.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.University of the North.mn201

The use of electronarcosis as anaesthetic in the cichlid, Oreochromis mossambicus (Peters). III. The effects of changing physical and electrical parameters on the narcotizing ability of half-wave rectified currents

The narcotizing potential of various rectified current configurations on Oreochromis mossambicus was investigated. A 50 Hz, 200 Vp. half-wave rectified current, applied for 30 s, was found to be a suitable configuration for electronarcosis.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.lmchunu2014mn201

Trout mortalities as a result of Streptococcus infection

Excessive mortalities were experienced in the bigger rainbow trout (Salmo gairdneri) at an efficiently managed trout farm. All tests for known toxins in the feed and water proved to be negative. A faecal Streptococcus which belongs to the Lancefield group D but which could not be identified as belonging to any of the recognized species within this group, was isolated from the spleens, livers and kidneys of affected fish. Pathogenicity studies with this organism proved it to be highly fatal to trout but not to Mozambique bream (Sarotherodon mossambicus), banded bream (Tilapia sparrmanii), carp (Cyprinus carpio) or largemouth bass (Micropterus salmoides). The isolation and biochemical characteristics of the organism are described. The symptoms, gross- and histopathology of this disease are described and discussed. The disease resembles a haemorrhagic septicaemia and appears to be associated with intensification and conditions of stress.This article has been scanned in colour with a HP Scanjet 5590; 300dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-Format