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Browsing by Author "Ansah, Yaw Boamah"

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    Characterization of pond effluents and biological and physicochemical assessment of receiving waters in Ghana
    Ansah, Yaw Boamah (Virginia Tech, 2010-04-09)
    This study was carried out to characterize ponds and aquaculture systems, and also to determine both the potential and actual impacts of pond aquaculture effluents on receiving stream quality in the Ashanti and Brong Ahafo regions of Ghana. Water, fish and macroinvertebrate samples were collected from upstream, downstream and nearby reference streams of, and questionnaires administered to, 32 farms. Total settleable solids were higher in ponds than reference streams (p = 0.0166); suspended solids was higher in ponds than reference streams (p = 0.0159) and upstream (p = 0.0361); and total phosphorus was higher in ponds than reference (p = 0.0274) and upstream (p = 0.0269). Total nitrogen was most clearly higher in ponds than all other locations: p = 0.0016, 0.0086 and 0.0154 for the differences between ponds and reference, upstream, and downstream respectively. BOD5 level was also higher in ponds than all locations (p = 0.0048, 0.0009, and 0.0012 respectively). Also, non-guarding fish species were more abundant in reference streams than downstream (p = 0.0214) and upstream (p = 0.0251), and sand-detritus spawning fish were less predominant in reference streams than upstream (p = 0.0222) and marginally less in downstream locations (p = 0.0539). A possible subsidy-stress response within study streams was also observed. Hence, ponds are potential sources of these water quality variables to receiving streams. Effluent-receiving streams, generally, were not much different from reference streams in terms of most the metrics of community structure and function used in the comparisons. Hence, even though receiving streams in Central Ghana may not be severely impacted by aquaculture effluents at the moment, the management of pond effluents will determine the scale of future impact. Vegetable, cereal, and livestock farming could serve as additional sources of fecal streptococci and coliform bacteria and nutrient-enrichment within the study area, besides aquaculture, and so these industries must also be included in efforts to minimize pollution of these streams.
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    Enhancing Profitability of Pond Aquaculture in Ghana through Resource Management and Environmental Best Management Practices
    Ansah, Yaw Boamah (Virginia Tech, 2014-12-09)
    The accelerating pace of growth of aquaculture in sub-Saharan Africa has received much positive appraisal because of the potential of the industry to contribute to economic development and food security by providing jobs and animal protein. Adoption of best management practices (BMPs) holds the potential to ameliorate the related environmental impacts of aquaculture, such as in the amounts of nutrients and sediment that will enter natural water bodies from earthen pond effluents. The goals of this study were to characterize adoption of aquaculture BMPs on small-scale, pond-based farms in Ghana, and to assess selected economic, social, and environmental outcomes of BMP adoption. Two BMPs: 1) water reuse, and 2) commercial floating feeds, were investigated for adoption by pond-based fish farmers in Ghana. I conducted my study in Ghana using on-farm experiments involving intensive monitoring of water quality and growth of Nile tilapia (Oreochromis niloticus) over two production cycles. Additionally, I administered a baseline survey to 393 (and a follow-up survey to 160) fish farmers. I determined the best model for modelling farmed Nile tilapia growth with multi-model inference based on Akaike information criterion (AIC), the profitability of adopting BMPs with stochastic enterprise budgets and, social welfare impact with the Economic-Surplus model. I used a Markov model to predict the equilibrium rate of adoption of the two BMPs and determined the impact of BMP adoption on the reduction of pollutant loading with the Minimum-Data method of the Tradeoffs Analysis (TOA-MD). My results showed that the logistic model is a better alternative to the von Bertalanffy model for modelling the growth of Oreochromis niloticus under pond aquaculture conditions. There were no significant differences in fish weight between the water re-use BMP and the use of new water. Adoption of the commercial floating feed BMP resulted in a 100% increase in fish final weight and yield, and in higher profitability, compared to the sinking feed type. Probability of making a profit was highest (72%) in the scenario with commercial feed and self-financing. Net present values (NPV) of about US$ 11 million and US$ 375 million could be obtained from the adoption of commercial floating feed and Genetically-Improved Farm Tilapia (GIFT) strain, respectively, in Ghana. Hence, any innovation that has a significant impact on fish yield also will have a significant impact on mean NPV and social welfare. However, I identified a number of potential negative ecological and genetic impacts exist from introducing the GIFT strain into Africa from Asia. Although considered low-intensity production systems, nutrients and solids in study ponds were found to be higher than levels expected in intensive culture ponds by wide margins. Pond water quality was significantly higher with commercial floating feed. The water-reuse BMP also prevented pollutants from leaving ponds altogether for the number of cycles for which pond water was reused, especially if associated BMPs such as rainfall capture and avoidance of water exchange are observed. Significant reductions in the loading of all water quality variables (nitrogen, phosphorus, solids, and BOD5) could be achieved with the adoption of the recommended feed type in Ghana. Adoption of the water reuse BMP has the potential to cause pollution reductions of 200% - 3,200% above that from the floating feed BMP. The strongest influence on the combined adoption of these BMPs were from : farmer's awareness of the feed BMP, perceived necessity and relative profitability of the water reuse BMP, and farmer's years of experience. A combination of central media (workshops), demonstrations, and lateral diffusion was found to be the most effective channel for disseminating these BMPs. Maximum adoption rate of the feed BMPs was estimated to be 38% - 58%. Also, US$ 6,000/year and US$12,000/year need to be paid per 0.6 ha pond surface area to push adoption of the feed BMP to 50% and 70%, respectively. Hence, to ensure the successful adoption of aquaculture BMPs, I recommend that regular well-planned workshops be organized to create awareness and a conducive atmosphere to target farmers at multiple stages of the innovation decision process. Incentives and effective dissemination will encourage the adoption of these and other environmental BMPs. Feed costs need to be lowered in order to encourage the adoption of commercial floating feed in Ghana. Future analyses could quantify the differences in production costs between using the two water types, to reveal the possible higher relative profitability of pond water reuse over draining ponds after each production cycle. Also, African governments are advised to commission rigorous baseline and ecological risk analyses before adoption of the GIFT strain. Improvements in management practices and infrastructure could increase the yield and profitability of the local strains even if genetically-improved strains are not introduced.