Producing tilapia in small cage in West Africa

This document is part of a series of 5 technical manuals produced by the Challenge Program Project CP34 ôImproved fisheries productivity and management in tropical reservoirsö. The Water Research Institute (WRI) in Akosombo, Ghana, is working to bring cage aquaculture technology to smallholder farmers. The stocking, feeding and cage-construction technology piloted by WRI is now being widely adopted in the Lower Volta basin in Ghana. The results of WRI research over the period 2005-2009 are presented here as a guide to potential investors.Cage culture, Gear construction, Stocking (organisms), Feeding, Havesting, Marketing

Nekton communities of an intertidal creek of an European estuarine brackish marsh

The utilization of an estuarine brackish marsh in the Westerschelde estuary (southwest Netherlands) by fish and crustaceans visiting the intertidal creeks at rising tides was investigated over an 18 mo period. Samples were collected every month over a tidal cycle. A stow net passively fished the nekton migrating in and out of the marsh habitat. Simultaneous measurements of current speed and waterheight allowed for quantification of the catches. Multivariate clustering and ordination techniques were applied to assess temporal changes in the nekton assemblage. A total of 68 fish and crustacean species were caught but only 38 were regular visitors of the marsh creek. The marsh nekton community proved to have a very stable character. Only 40% of the observed variance could be explained. The seasonal appearance of juvenile stages of fish and crustaceans was found to differentiate between spring and summer-autumn communities. The environmental variables measured (i.e. temperature, salinity, oxygen concentration and detritus standing stock) did not correlate well with the observed changes in community structure. The mysid shrimp Neomysis integer dominated the community, both in density and biomass, during most of the year. Early postlarval flounder Pleuronectes flesus characterized the spring nekton assemblage. Early postlarval brown shrimp Crangon crangon was abundant from spring through autumn. In late summer juveniles of seabass Dicentrarchus labrax, common goby Pomatoschistus microps and shore crab Carcinus maenas were typical members of the marsh creek nekton. The hyperbenthic fauna of the marsh was comparable to the hyperbenthos found in the adjacent subtidal parts of the Westerschelde estuary while the epifauna of both areas differed substantially. It is argued that the marsh under study is a nursery ground for only a small number of estuarine inhabitants: C. crangon, P. flesus, C. maenas, P. microps, D. labrax and possibly 2 mullet species. Adult flounder, adult and juvenile common goby, juvenile seabass and the early postlarval brown shrimp all use the creeks as feeding ground, mainly preying upon the creek infauna and mysids. Given the high abundance of hyperbenthic mysid shrimp in the marsh and their presumed role in detritus-based food chains, we believe marsh studies should not refrain from considering this component of the nekton. This is the first study reporting on the nekton use of a European marsh. The need for similar research in other European marshes is stressed

Engaging local communities in aquatic resources research and activities: a technical manual

This document is part of a series of 5 technical manuals produced by the Challenge Program Project CP34 “Improved fisheries productivity and management in tropical reservoirs”. The objective of this technical manual is to relay the field experience of a group of scientists who have worked extensively in small fisheries in sub-Sahara Africa and Asia and lay out a series of simple and pragmatic pointers on how to establish and run initiatives for community catch assessment. The manual relies in particular on practical experience gained implementing Project 34 of the Challenge Programme on Water and Food: Improved Fisheries Productivity and Management in Tropical Reservoirs. (PDF contains 26 pages

Engaging local communities in aquatic resources research and activities: a technical manual

This document is part of a series of 5 technical manuals produced by the Challenge Program Project CP34 ôImproved fisheries productivity and management in tropical reservoirsö. The objective of this technical manual is to relay the field experience of a group of scientists who have worked extensively in small fisheries in sub-Sahara Africa and Asia and lay out a series of simple and pragmatic pointers on how to establish and run initiatives for community catch assessment. The manual relies in particular on practical experience gained implementing Project 34 of the Challenge Programme on Water and Food: Improved Fisheries Productivity and Management in Tropical Reservoirs.Research, Fishery data

Improved fisheries productivity and management in tropical reservoirs

“Improved fisheries productivity and management in tropical reservoirs” The objective of the project was to contribute to the current research on reservoirs enhancement fisheries in tropical countries through the implementation of a series of action-research activities implemented in two small reservoirs in the Indo-Gangetic basin in India, and two very large reservoirs in Africa, the Lake Nasser (Egypt), and the Volta Lake (Ghana). Socio-institutional analyses were also conducted in these reservoirs to improve our knowledge regarding some of the main social processes that influence reservoir productivity. Overall the results of the project stress that while the natural biophysical constraints of the reservoirs are important in defining the ecological production processes, it is the socio-economic settings characterizing the community/societies around the reservoirs that eventually shape the human production enhancement possibilities

Improved fisheries productivity and management in tropical reservoirs

The main objective of this 3.5 year project was to increase the productivity of reservoir fisheries and provide sustainable livelihoods to the rural poor through a series of interventions in tropical reservoirs. The main project activities focused on two reservoirs in the Indo-Gangetic basin (Dahob in Madhya Pradesh, and Pahuj in Uttar Pradesh, both in India), the Lake Nasser in Egypt as part as the Nile basin, and the Volta Lake in Ghana as part as the Volta basin. The project also encompassed an initial data inventory from a wide variety of tropical reservoirs within the three basins, and the detailed assessment of the selected reservoirs, including market evaluation and post-capture improvements. (PDF contains 117 pages

Nursery function of an estuarine tidal marsh for the brown shrimp <i>Crangon crangon</i>

The brown shrimp Crangon crangon migrates into the brackish part of the Westerschelde estuary (southwest Netherlands) shortly after metamorphosis and uses the tidal marsh habitat as a nursery until reaching a total length of about 15mm. The importance of the marsh as a nursery was evaluated by estimating foraging activity, predation mortality and residence time. In early postlarval stages, C. crangon utilised the intertidal creeks of an estuarine tidal marsh from early spring (March-April) until late autumn (October-November). Postlarval shrimp leaving the marsh with the ebb tide always had significantly more food in their stomachs than shrimp entering the marsh with the incoming flood water. Predation upon the shrimp population was relatively low during most months, but it increased between August and October when common gobies, Pomatoschistus microps, were present in high densities. There was also predation by the small seabass Dicentrarchus labrax. The marsh creeks function both as foraging areas and as predation refuge. Depending on temperature, postlarval shrimp stayed in the marsh for a period of two to three weeks. Quantitatively, the value of the marsh as a nursery area had changed drastically during a second year of sampling, illustrating high natural year-to-year variability. However, the seasonal pattern remained. Recruitment to the subtidal adult population represents an export of animals from the marsh to the estuary. This export is negligible in terms of biomass (as compared to the total biomass of the estuarine population) but it may be important in terms of numbers of individuals