Aims: To determine the profitability of using a commercial tilapia feed to produce three different size ranges (1.0-1.9, 2.0-2.9 and 5.0-5.9 g) of Nile tilapia, Oreochromis niloticus fingerlings in hapa-in-pond system. Study Design: Completely randomized design. Place and Duration of Study: The Aquaculture Research and Development Centre (ARDEC), Akosombo, of Water Research Institute (WRI) of Council for Scientific and Industrial Research (CSIR), Ghana, from March to May, 2020. Methodology: Fish growth study was carried out in three (3) fine mesh netting hapas, each of dimensions 5.0 x 2.0 x 1.2 m. Nile tilapia fry at initial mean weight 0.03 ± 0.01 g were stocked at a density of 50 fish m-2 and they were fed at 20 % body weight five times daily. The feeding of the fish continued until those in all the 3 hapas attained a mean weight of at least 5.0 g. Then the experiment was terminated and all the survived fish in each hapa were harvested, counted, and their individual body weights were measured. Growth performance indicators and profitability of producing the various size categories (1.0-1.9, 2.0-2.9 and 5.0-5.9) were determined. Results: The fry attained the target size ranges of 1.0-1.9, 2.0-2.9 and 5.0-5.9 g in 4, 6 and 9 weeks respectively. There were significant differences (ANOVA, P = 0.03) among final mean weights, weight gains, feed intakes, daily weight gains, feed efficiencies and harvested biomass among all size ranges, with those of 5.0-5.9 g being significantly higher (Tukey’s HSDT, P < 0.02). Sizes of fingerlings produced correlate positively with cost of feed used. The profit indices ranged from 2.57 to 10.22, with the highest recorded in the 1.0-1.9 g fingerlings and the least in those of 5.0-5.9 g. Conclusion: The results indicated that, at the current Nile tilapia fingerlings cost and the time taken to produce the various size categories, the 1.0-1.9 g production is the most profitable.
Geometry of fish tanks tends to affect the growth and yield of fish. The impact of tank geometry on the production of Clarias gariepinus was evaluated. Circular, rectangular and ellipsoid tanks were used to test the variation of water temperature, pH, dissolved oxygen and total suspended solids on African catfish growth performance. Results on water temperature, pH, DO, were within the acceptable ranges of 24.9-25.9°C, 6.39-7.52 and 5.81-8.32 mg/l, for circular tank; 25.1-26.1˚C, 6.49-7.53 and 3.96-8.53 mg/l, for rectangular tank; and 24.5-26.2°C, 6.49-7.50 and 5.08-8.43 mg/l, for ellipsoid tank; respectively. Weight gain ranged from 14 to 576 g, 13 to 330 g and 14 to 557 g; feed conversion ratio (FCR) ranged from 1.11-1.33, 1.23-1.54 and 1.22-1.34; specific growth rate (SGR) ranged from 0.40 g/day to 3.64 g/day, 0.11 to 2.27 g/day and 0.79 to 3.12 g/day; survival rate were >88, >84 and >92% for circular, rectangular and ellipsoid tanks, respectively. Except for weight gain and FCR, all other parameters (length increment, SGR and survival rate) showed no significant difference (P = .05) among the 3 tank geometries. Benefit cost ratio (BCR) for the circular, ellipsoid and rectangular tank was 1.12, 1.13 and 0.79, respectively.
Understanding aquatic ecosystem dynamics is fundamental to sustainable development of aquaculture. This study explores the water quality characteristics over temporal and spatial scale in Tono and Vea Reservoirs in the Upper East Region of Ghana for aquaculture development. Water samples and in-situ measurements were taken for fifteen months, from February 2015 to March 2016. Monthly water quality monitoring were based on stratified sampling from upstream, midstream and downstream zones of these reservoirs. Standard analytical methods for examination of water were employed during sampling and laboratory analysis of reservoir water quality. Phytoplankton analysis was done using light microscopy to obtain phylum abundance. Multivariate statistical methods were used to investigate water quality dataset obtained. Cluster analysis grouped fifteen months of water quality changes into three seasonality regimes (periods) based on temporal variation. Principal component analysis (PCA) reduced eighteen water quality variables into five and three factors with total variance of 88.26 % and 79.30% for Tono and Vea reservoirs, respectively. With pH > 7 and alkalinity > 20 but < 100 mg L-1 CaCO3, both reservoirs have alkaline water. Dissolved oxygen was > 5 mg L-1. Three phyla of phytoplankton were identified with dominant (in abundance) phylum as Chlorophyta (72%) occurring in Tono reservoir. To understand the spatial relationship using correspondence analysis (CA), the first axis of CA explained 84.2% and 64.3% of total variation in relative abundance of phytoplankton phyla for Tono and Vea reservoirs, respectively. Thus, Cyanophyta showed strong positive association with conductivity, total hardness, nitrate, sulphate, turbidity, water depth and dissolved oxygen which were responsive to the midstream and upstream zones of Tono reservoir. Whiles in Vea reservoir, Chlorophyta under same water quality variable showed responsiveness to the midstream and downstream zones. Reservoir water quality studied were within acceptable limits for fish culture but changes could be linked to anthropogenic activities on reservoir catchment area and seasonality regime. Results from this provide a baseline to enable information to enable assessment of aquaculture impact in Tono and Vea reservoirs. The use of multivariate analysis could be a reliable statistical method for assessing water quality on a spatio-temporal scale.
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