A preliminary assessment of water quality in fish cages on Lake Kariba, Zimbabwe (original) (raw)
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Journal of Great Lakes Research, 2011
The initiation of cage aquaculture in the shallow southeast arm of Lake Malawi has raised concerns about its possible impact on the surrounding environment and the highly diverse fish community. To evaluate the impact of the cage operation on the surrounding environment, observations were made over an annual cycle in 2007 at a production capacity of~200 tonnes fish/year. Impacts of the cage wastes in the water column in the vicinity of the cages were minimal despite the substantial discharges from the cages. No significant differences were observed in concentrations of dissolved and particulate nutrients (ammonia, nitrate, phosphate, particulate C,N and P), chlorophyll, chlorophyll fluorescence, dissolved oxygen, total suspended solids, Secchi depths and extinction coefficient of photosynthetically active radiation between the cage site and the control stations upstream or downstream of the fish farm. Although sedimentation rates measured in traps were higher under the cages than at control sites, the sediment flux was a small percentage of total feeds added to the cages. Apparently cage wastes were efficiently dispersed by water currents which averaged 9.3 cm/s below the fish cages. Consumption of the wastes by wild fish species which aggregated around the fish cages and their movement in the vicinity of the cages also contributed to the dispersion of the cage wastes and served to dilute impact of the cages. In combination, these physical and biological processes reduced the immediate impact of the cage farming operation and must be considered in the siting of future cage farms.
Uganda Journal of Agricultural Sciences
Growing of fish in cages is currently practiced in Uganda and was first introduced in northern Lake Victoria in 2010. An environment monitoring study was undertaken at Source of the Nile, a private cage fish farm, in Napoleon gulf, northern Lake Victoria. In-situ measurements of key environmental (temperature, dissolved oxygen, pH and conductivity) and biological (algae, zooplankton, macro-benthos) variables were made at three transects: Transect 1-the site with fish cages (WC); transect 2-upstream of the fish cages (USC-control) and Transect 3-downstream of the cages (DSC). Upstream and Downstream sites were located approximately 1.0 km from the fish cages. Environment parameters varied spatially and temporally but were generally within safe ranges for freshwater habitats. Higher concentrations of SRP (0.015-0.112 Mg/L) occurred at USC during February, September and at DSC in November; NO 2-N (0.217-0.042 mg/L) at USC and DSC in February and November; NH 4-N (0.0054-0.065 Mg/L) at WC and DSC in February, May and November. Algal bio-volumes were significantly higher at WC (F (2,780) =4.619; P=0.010). Zooplankton species numbers were consistently lower at WC with a significant difference compared to the control site (P=0.032). Macro-benthos abundance was consistently higher at the site with cages where mollusks and low-oxygen and pollution-tolerant chironomids were the dominant group. Higher algal biomass, concentration of low-oxygen/pollution-tolerant macro-benthos and depressed zooplankton diversity at WC suggested impacts from the fish cages on aquatic biota.
Abstract This study examines the effect of physicochemical parameters on different categories of fish species; benthopelagic, pelagic and demersal on Lake Volta. The methods of this study were based on the estimation of hydrographic data, collection and analysis of physicochemical parameters of the water samples. Fish samples were collected from four sampling stations namely Oti River at Sabra, White Volta at Daboya, Black Volta at Bamboi and Lower Volta at Amedeka. This review work studies a study which was carried out between February 1995 and January, 1996. A statistical analysis was conducted. Water resource availability and mean annual rainfall of Lake Volta were highest in Black Volta and Oti River respectively. The results show pH 194-520, Conductivity (μS cm-1), Dissolved oxygen 8.0- 11.2 (mg/L), Biological Oxygen Demand (BOD) 2.7-105 (mg/L), Alkalinity 35.3-53.8 (mg/L), Chloride 4.6-13.6 (mg/L), Calcium 4.8-10.1 (mg/L), Total Hardness 17.4-44.1 (mg/L), Magnesium 2.5-8.3 (mg/L), Ammonia-N 0.4-1.6 (mg/L), Phosphate 0.2-0.9 (mg/L), Nitrate 0.2-6.6 (mg/L), Nitrite 0.06-0.6 (mg/L) and Sulfate 1.2-8.9 (mg/L) respectively. The benthopelagic, pelagic and demersal fish population show 16, 6 and 11 number of different fish species respectively in the lake. The study concludes that the quality of the water is satisfactory when compared with other lakes. Anthropogenic activities is insignificant on the aquatic habitat and the appreciable fish population is an indication of good biological quality of the water body.
Impacts of cage culture on physico-chemical and bacteriological water quality in Lake Volta, Ghana
African Journal of Aquatic Science, 2016
The effects of cage fish farming on physico-chemical and bacteriological water quality in Lake Volta, Ghana, were investigated in 2013-2014. Farmed and unfarmed (control) areas of the lake were selected for monitoring. Nutrients, temperature, dissolved oxygen, conductivity, turbidity, pH, total coliforms, Pseudomonas and Vibrio spp. in the water were monitored monthly. Analyses of the water samples were carried out according to standard procedures. Physico-chemical quality of the water in both farm and control sites were within ranges typical of minimally impacted water and did not vary significantly between the two contrasting sites. The bacteriological analysis, however, revealed contamination of the lake water by fish farming. The bacterial counts at the farmed sites were significantly higher (p < 0.05) than those of the control sites, with figures at the farmed sites ranging from 132 to 1 708 cfu 100 ml −1 for total coliforms, 514 to 5 170 cfu 100 ml −1 Pseudomonas spp. and 14 to 516 cfu 100 ml −1 for Vibrio spp. The results suggested that cage fish farming has increased bacterial loads in the lake water, but has had minimal impact on its physico-chemical quality.
In recent years, Lake Kossou has been subject to heavy human activities, including clandestine gold panning and the extensive application of nutrients related to the repetitive fish farming activities of the fish farm in floating cages on the lake. Objectives: This study thus aims to evaluate the influence of fish farming activities on the ecological quality of the waters of Lake Kossou on the basis of physico-chemical parameters. Methodology: The physico-chemical parameters of the waters of the floating fish farm on Lake Kossou were studied on a seasonal basis between 12 May 2017 and 26 February 2018. In-situ measurements and chemical analyses were carried out on water samples taken from 0 to 6 m deep in the lake waters. Results: Analyses show that the waters of Lake Kossou have a low transparency ranging from 0.62 to 1.5 m with high nitrate concentrations ranging from 0.82 to 7.02 mg/l. The two main seasons were characterized by high values of temperature, pH, nitrate and dissolved oxygen content. The stratification of temperature, pH, dissolved oxygen and nitrate content revealed the presence of a metalimnetic layer at a depth of 2 to 3 m in Lake Kossou. Conclusion: Data obtained from nutrient salts and transparency therefore characterize the advanced trophic status of Lake Kossou.
Physicochemical analysis and fish pond conservation in Kano State, Nigeria
The health of an artificial or natural fish pond is determined by the state of its physiochemical parameters. This study was therefore, designed to examine the level of physicochemical regime of four selected fish ponds, viz; Zogarawa fish pond, Bagauda fish seed multiplication centre, Fagam fish pond and Khasu integrated fish pond in Dawakin Tofa, Bebeji and Kumbotso Local Government Areas of Kano State from July 2014 to December 2014 (rainy season and harmattan season). The techniques for determining the parameters were as described in the instructional manual of the HANNA Instruments (HI ©) and JENWAY(®) Water Analysis Kits. The physicochemical parameters of the pond water was analyzed and determined using one way analysis of variance (ANOVA) with the aid of INSTAT 3 statistical software for window version 2003. The values of the physicochemical parameters of four fish ponds in the study area were between 25.7±1.07 to 27.8±1.03 o C for temperature, 6.8±0.03 to 7.1±0.62 for pH, 2.01±0.03 to 3.08±0.13mg/L for dissolved oxygen, 296.3±1.73 to 613.7±3.03 µs/cm for electrical conductivity, 63.0±1.90 to 153.0±2.76mg/L for total hardness and 20.5±2.35 to 100.6±4.98mg/L for total suspended solids. There was no significant difference (p>0.05) in the levels of temperature, pH and dissolve oxygen but there is significant difference (p<0.05) in electrical conductivity, total hardness and total suspended solids between the ponds. The studied ponds are in a stable state and suitable for fish farming with the idea of re-introduction into water bodies with insufficient fish populations.
Effect of Water Quality Characteristics on Fish Population of the Lake Volta, Ghana
Journal of Environmental & Analytical Toxicology, 2015
The Volta Lake is located in Ghana, West Africa. It lies between latitudes 5°30´N-14°30´N and longitudes 2°00´E-5°30´W, which stretches for a length of 520 km 2 from the Northern part to the southern part of Akosombo dam [7]. It is part of a river basin component which occupies 417,382 km 2 and follows a part of a basin which is elevated from sea level to a height of 920 m to an average elevation of 257 m
This study aimed to assess the impact of the cage fish farming on the water quality in two selected bays of the Bukavu basin, Lake Kivu; from February to December 2021. Physicochemical parameters including pH, Temperature, EC, TDS, Salinity, DO, Transparency were sampled in situ using a COMBO HI 98129 multi-parameter probe, PCE-PHD1 probe and a Black & White Secchi disk; water at different depths was collected with the aid of a Van-Dorn Sampler; nutrients namely PO43−, NH4+, NO2−, SiO2, and Chl_a were analysed using the UV-VIS spectrophotometer. The results revealed that water pH, temperature, TDS, salinity and transparency significantly (p ≤ 0.05) varied between the selected sites. Water at the cage sites contained significantly (p ≤ 0.05) much higher concentrations of PO3 − 4, NH4+, NO2−, SiO2 and Chl_a than in control site. In overall, these results suggest that cage fish farming changed water quality in the selected bays. Therefore, the study recommends that measures should be t...
International Journal of Biological and Chemical Sciences, 2014
Physicochemical indices of water body changed seasonally and this necessitated an investigation to assess the water quality parameters of Osinmo reservoir in relation to its fish species. The water quality parameters were measured using standard methods. Results obtained show that the reservoir is alkaline in nature with dissolved oxygen concentration (1.8-7.2 mgl-1) and alkalinity (64 CaCO 3 mgl-1-108 CaCO 3 mgl-1) which were within the optimum range for growth and survival of fish. Four families of fish comprising eight species were encountered. The sex-ratio of five species which were statistically different (P<0.05) indicated reproductive efficiency populations while other fish species whose sex-ratio differed insignificantly (P>0.05) revealed a growing population. The well-being of the fish species was adequate as observed in the least mean condition factor of 0.666±0.057 in C. gariepinus and the highest mean of 2.000±0.242 in S. galilaeus. The productivity of the reservoir can be improved through proper management of the water body.