The evaluation of cage fish farming effects on water quality using selected benthic macro-invertebrate community parameters in the napoleon gulf, northern Lake Victoria (original) (raw)
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Since the proliferation of cage fish farming in Uganda has raised concern over water quality deterioration, a study of the effects of cage fish farming on water quality in the Napoleon Gulf, Northern Lake Victoria was conducted during October 2012 to February 2013. Selected water column physico-chemical parameters and benthic macro-invertebrates' community parameters (i.e. numerical abundance, Shannon-Weaver diversity Index and modified Hilsenhoff Biotic Index) were analyzed monthly at both cage and non-cage sites. No significant differences were observed in physico-chemical parameter values, benthic macro-invertebrates' numerical abundance and Hilsenhoff Biotic Index between cage and non-cage sites. On the other hand Benthic macro-invertebrate species diversity differed significantly between the reference site and cage site 2 (P<0.05). Pollution tolerant Chironomus sp. and Melanoides tuberculata Muller, 1774 were significantly higher at the cage sites than the non-cage s...
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.
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...
Environmental impacts of cage culture in Lake Victoria: the case of Shirati Bay‑Sota, Tanzania
Abstract The experimental cage culture was conducted at Shirati bay, Lake Victoria from February to August 2013, to investigate the impacts of the small scale cage culture on the environment. Three locations along the cages, at the intermediate and one in the offshore (control) were sampled for water quality parameters, phytoplankton and macro invertebrates. A notable increase in nutrient concentration was observed after the set of cages among the stations. However DO, pH, and water transparency showed no major changes and was within the recommended ranges. Cyanophytes an indicator of inorganic pollution dominated before and after the set of cages, an increase in phytoplankton numerical abundance was observed after stocking of fish in cages. In addition there was an increase in the invertebrate community especially bivalves and gastropods. In conclusion we found no consistent environmental change caused by cage culture, and therefore it can be allowed in Lake Victoria, Tanzania part, with close monitoring of its impacts. Keywords: Cage culture, Nutrient enrichment, Water quality, Waste food
Aquaculture, 2011
The potential impact of Nile Tilapia (Oreochromis niloticus) cage culture on water quality and pelagic community composition was investigated in two Ethiopian small water bodies, one located in the highlands (Yemlo) and the other in the Great Rift Valley (Allage). This study was designed to assess the difference between the cages and open water in relation to those water quality changes attributable to intensive inputs of fish waste and left-over fish feed. All physico-chemical water quality parameters including inorganic nutrients varied temporally, coupled with dry and wet periods. The reservoir's trophic state ranged from eutrophic to hypereutrophic, with a strong correlation between chlorophyll-a and total phosphorus. The phytoplankton community was dominated by Cyanobacteria (84% of total phytoplankton abundance), in particular by Anabaenopsis sp. in Allage reservoir, whereas Chlorophyta (70%), with Pediastrum simplex as the dominant taxon, prevailed in Yemlo reservoir. A total of 23 zooplankton taxa were recorded during our sampling; rotifers were the richest group with 14 taxa distributed in 6 genera, followed by cladocerans represented by 6 taxa (5 genera) and copepods by 3 taxa (1 genus). Dissolved inorganic nutrient concentrations and other physical parameters showed no significant differences between the cages and open water. The exceptions were dissolved oxygen and ammonium nitrogen, which were lower and higher in the cages, respectively. For the whole study period of 240 days, the mean net weight and daily growth rate per fish were 183.3 g and 1.1 g d − 1 , respectively.
Lakes & Reservoirs: Research & Management, 2013
Spatio-temporal variations of phytoplankton, expressed in terms of species composition and diversity collected at various sampling sites in small water bodies (SWBs) within Lake Victoria basin, Kenya, were investigated monthly from November 2010 to June 2011, in relation to selected physical and chemical water quality parameters. Temperature, D.O, TN and TP revealed a significant difference between the dams (p<0.005) unlike pH and BOD 5. These SWBs were built during the pre-independence era and stocked with various species of fish. The dams provide water for both domestic and agricultural use. A total of 1392 phytoplankton species belonging to four families and 20 genera were identified in Kesses dam whereas in Kerita dam, a total of 376 phytoplankton species belonging to four families and 10 genera were identified. In Siaya dams, Yenga dam had three families of phytoplankton; Chlorophyceae, Euglenophyceae and Cyanophyceae with Mauna also recording four families: Chlorophyceae, Bacillariophyceae, Desmidiaceae and Cyanophyceae. All the SWBs generally registered low species diversity with majority of them recording a value of < 2. Seasonal variations in phytoplankton species composition and diversity were significant (P < 0.05) with low species composition and diversity occurring during the dry season, and being maximum following the end of the rainy season from November 2010 to March 2011, suggesting the possible influence of various environmental factors on the SWBs. Overall, water quality seemed to have had effect on the species diversity, dominance and richness of phytoplankton community structure.
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.
Impact of Cage Aquaculture on Water Quality Condition in Lake Maninjau, West Sumatera Indonesia
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Water quality characteristic of Lake Maninjau related to the deterioration condition has been intensively reported, nevertheless research on water quality as an impact of cage aquaculture level has never been done. The aim of this research was to identify influence of cage density to water quality condition. The study was conducted at 11 stations in Lake Maninjau, by measuring 11water quality parameters at a depth of 4.5m and sediment organic content on locations that have soft substrate. Measurement periods were on June 2013, September 2013, December 2013, and March2014. Activity of cage aquaculture was distributed in all over the lake shore lines, with the highest density at 1226 units km-1. Water quality measurement indicated similar condition based on spatial patterns (degree of similarity >85%) with tendency that the increase number of cages influence several parameters including increase concentration of chemical oxygen demand (COD), total nitrogen, and ammonium; and decrea...
The Scientific World Journal, 2022
Biological monitoring of reservoirs is important in assessing aquatic health. is study aimed at assessing the structure of benthic macroinvertebrate communities in relation to physicochemical parameters along Sanyati basin shoreline in Lake Kariba, Zimbabwe. Six sites (S1 to S6) characterized by various human disturbances were sampled for physicochemical parameters and benthic macroinvertebrates from January to March 2018. We computed macroinvertebrate metrics and classi ed them into functional feeding groups (FFGs). A canonical correspondence analysis (CCA) triplot was constructed to assess speciesphysicochemical relations. Signi cant di erences across the sampling sites were observed for pH, electrical conductivity, turbidity, nitrate-nitrogen (NO 3-N), ammonium nitrogen (NH 4-N), total nitrogen (TN), phosphate-phosphorus (PO 4-P), total phosphates (TP), and dissolved oxygen (DO). e results from CCA highlighted that S1 was generally associated with high pH, NH 4-N, and TN, and Oligochaeta, Syrphidae, and Hydrophilidae families. e highest percentage of EPT taxa (39.83%) was recorded at S6, while the lowest was recorded at S1. e taxa were made up of 50% predators, 26% collector-gatherers, 6% scrappers, 6% shredders, and 3% collector-lters with 3 taxa (Chironomidae, Hydropsychidae, and Leptoceridae) having more than two FFGs. Site S1 had a signi cantly higher mean abundance of collector-gatherers than the other sites. A high correlation between water parameters and SASS and ASPT scores was observed indicating their ability to detect environmental changes. ese ndings suggest that macroinvertebrate communities are good candidates for delineating the e ects of industrial pollution on water quality.