Studies on the effects of environmental factors and selected pathogens on morbidity and mortality of hatchery reared Oreochromis mossambicus (Peters) eggs and fry

The dynamics of the physical, chemical and microbiological parameters of hatchery water and their effects on the hatchability and survival of artificially incubated eggs and fry of O. mossambicus in two different recirculatory systems was studied. The tolerance levels of fry stages to important physical and chemical parameters of hatchery water were also estimated. The susceptibility of yolksac fry appeared to increase as they developed and utilised yolk. The egg mortalities were found to be initiated by mechanical injuries to the ohorionic membrane which subsequently attracted bacterial colonisation; the primary cause of death. Fungal infections appeared to have only a secondary role. This mechanism was elucidated using microbiological and SEM techniques. Chemical disinfectants and ultraviolet sterilisation of hatchery water were tested in controlled experiments and an assessment of their relative efficiency in improving hatchability was made. Anti-bacterial activity of the buccal end skin mucus of brooding O. mossambious females was investigated with the view to understanding the protection offered to the progeny whilst brooding. No antibacterial activity could be demonstrated. Experimental infections of Q.mossambicus with I.multifiliis were carried out and lethal and sublethal levels of infections for various age groups of fish were estimated. The sequential pathology of sublethal infections of I.multifiliis on O.mossambicus fry was studied. Adult O. mossambicus females were effectively immunised against I.multifiliis by controlled infections. Antiparasitic factors were demonstrated in both serum and mucus only in immunized fish. Evidence for a specific acquired immune response of humoral origin was found and its implications for aquaculture were discussed. A protection offered to the fry by the immunized females against I.multifiliis infections whilst brooding was demonstrated. This appeared not to operate through a transfer of passive immunity from mother to fry. Alternative mechanisms are suggested

Best Management Practice guidelines (BMPs) for GIFT tilapia & Curriculum for the Promotion of Commercial Aquaculture in Nigeria

As part of the GIFT-related WorldFish projects operating in Nigeria, there is a need for developing (a) BMPs and related guidelines, and (b) training material to train stakeholders to implement BMPs in Nigeria. This manual includes best management practice guidelines for GIFT tilapia hatchery and grow out operations, including the curriculum for BMPs

Effects of nitrite and pH on a tropical fish fry, puntius gonionotus (Bleeker)

The effects of short term and long term exposure of a tropical fish fry, Barbodes gonionotus (Bleeher), to pH and nitrite separately and in combination, were evaluated using static and flow-through bioassays respectively. The 96-hour LC50 values of pH and nitrate were 4.9 and 7.91 mg/l N02-N -respectively. However the 96-hour LC50 of pH was higher (5.4 pH unit) in the presence of nitrite 5.00 mg/l N02-N) than that without nitrite. At pH 5.00,100% mortality was found at 4.00 mg/l N02-N concentration after 48-hour exposure. Under long-term exposure, the growth rates of the fish fry decreased with increased nitrite concentrations. Fish fry grown at 2.00 mg/l N02-N had significantly lower growth rate (P < 0.05) than the control, but had a significantly higher rate (P < 0.05) than in the 4.00 mg/l N02-N (PH 7.33-7.56). One hundred per cent mortality occurred within 30 days at pH 5.00 - 7.00 when the fish were exposed to 4.00 mg/l N02-N concentration at the same time. The study demonstrated that the effects of combined pH and nitrite on the survival and growth rates of the fish fry were more serious than the effects of each factor separately

Performance analysis of existing catfish and tilapia value chains and market systems in Nigeria: A post-farmgate value chain scoping study

Nigeria is the largest fish producer in Sub-Saharan Africa. Fish plays a crucial role in supporting the livelihoods of fish producers and actors along the post-farmgate value chain in the country. Despite the virtues of the aquaculture and fisheries subsectors to enhance the livelihoods of value chain actors, major gaps exist related to efficiencies of the fish value chain. These gaps include the financial performance of post-farmgate actors, gender-disaggregated data on value chain actors, the roles of women and youths in fish trade, and post-farmgate food safety practices. The aim of this study is to fill the data gap in the post-farmgate fish value chain to provide evidence-based policy suggestions to enhance the aquaculture subsector in Nigeria. Using primary data, our study provides evidence on the economic, environmental, social, nutritional and food safety performance of the post-farmgate fish value chain. Our study finds that, in general, fish value chains are economically viable (profitable) and inclusive, as women and youths own over half of post-farmgate value chain activities. These results are of interest to both private and public sector decision-makers and policymakers because they provide quantitative data on value creation (fish sales, employment, service provision), social performance (women and youth empowerment), and environmental, nutritional and food safety challenges along fish value chains

Chemicals in Asian aquaculture: need, usage, issues and challenges

This paper outlines the opening introductory presentation made at the “Expert Meeting on the Use of Chemicals in Aquaculture in Asia,” which was held 20-22 May 1996 at the SEAFDEC facilities in Tigbauan, Iloilo, the Philippines. Its purpose is to provide a balanced and realistic perspective on the needs, issues and challenges with respect to the use of chemicals in Asian aquaculture. We hope to assist participants in identifying development opportunities and in differentiating real hazards from hypothetical threats to cultured organisms, end-users and the environment as a consequence of chemical use. We do not attempt to provide answers to issues related to chemicals in Asian aquaculture, but rather offer some basic directives and opportunities to the workshop participants to assist them in their discussions and in the compilation of realistic recommendations

Changes in Aquaculture

Global aquaculture production in 2017 (animals and plants) was recorded as 111.9 million tons, with an estimated first-sale value of $249.6 billion. Since 2000, world aquaculture has ceased to enjoy the high annual growth rates of the 1980s and 1990s (11.3 and 10.0 per cent, respectively). Nevertheless, it continues to grow at a faster rate than other major food production sectors. Annual growth declined to a moderate 5.8 per cent during the period from 2000 to 2016, although double-digit growth still occurred in a small number of countries, in particular in Africa, from 2006 to 2010. Fish produced by this rapidly growing sector is high in protein and contains essential micronutrients, sometimes essential fatty acids, which cannot easily be substituted by other food commodities...Fil: Subasinghe, Rohana. Futurefish; Sri LankaFil: Baron, Pedro Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Beveridge, Malcom. Malcom Beveridge Independent Consultant; Reino UnidoFil: Marschoff, Enrique Ricardo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Oliva, Doris. Universidad de Valparaíso; Chil

Biosecurity: Reducing the burden of disease

Abstract The challenges and problems of managing good biosecurity are wide‐ranging and multifactorial with many compounding factors to pre‐dispose farmed stocks to an increased risk of infection with consequential stock losses. Many challenges are anthropogenic in origin and may be the result of the physical location (site) and/or the poor design of the production facility (i.e., water re‐use; lack of zoning based on biosecurity risk, etc.) as well as from inappropriate decisions and practices made once the site is in production (i.e., pushing the system for increased biomass production). There is a need for better regulation and health legislation across aquaculture—an industry that embraces the culture of >500 species. In the absence of regulatory frameworks and culture guidelines, it is difficult for farmers to apply certain measures such as maximum stocking densities and maximum allowed biomass, conduct disease surveillance and regular health checks, and report diseases to relevant authorities for advice. In this review, we have identified several issues which are continuing to challenge the design and implementation of efficient and effective biosecurity strategies and protocols at all levels, requiring attention over the coming decade. They are, not in any order of priority: (a) healthy seed, (b) emergency preparedness and response, (c) diagnostics, (d) microbial management at the production level, (e) disease and pathogen surveillance, (f) trade in aquatic species, (g) policies and regulatory framework, (h) welfare, (i) research and technology development, (j) antimicrobial resistance, (k) non‐conventional ways of pathogen transfer, and (l) Progressive Management Pathway