The culture of seabass

Seabass (Lates calcarifer) are raised in ponds and cages in Southeast Asia. Details are given of the 2 phases involved in the pond and culture culture systems -- nursery and grow-out. Both monoculture and polyculture systems are used for pond production of seabass. Polyculture may involve milkfish and tilapia, groupers, seaweed, tilapia or snapper, grouper and shrimp.

AQD recommends semi-intensive milkfish culture

Details are given of a system for semi-intensive milkfish (Chanos chanos) vulture recommended by the SEAFDEC Aquaculture Department, under the following headings: 1) Pond preparation; 2) Pest (snails) control; 3) Pest (tilapia and other fish) control; 4) Fertilizer application; 5) Stocking density in nursery ponds; 6) Stocking density in grow-out ponds; and, 7) Water management.

Economic value of the milkfish industry

A brief description is given of the milkfish (Chanos chanos) farming industry in the Philippines. Over the past 20 years, the relative importance of milkfish has declined with the expansion of tilapia, tiger shrimp and seaweed farming. In 1975, some 141,461 mt of milkfish made up 10% of the total fish production, whereas in 1995, the total milkfish harvest of 150,858 mt made up only 5.5% of the total fish production. Milkfish are harvested and marketed mostly fresh or chilled, whole or deboned, but some are canned or smoked. The domestic markets, mainly in Metro Manila, absorb most of the production. Milkfish is also absorbed in different product forms: dried, canned, smoked, or marinated. An export market for quick-frozen deboned milkfish fillets has begun to develop and fish processing companies are responding fast. The milkfish farming industry has important linkages with the various sectors that supply the inputs, and those that transport, store, market or process the harvest. For intensive milkfish farming to be both profitable and sustainable, more value-added products must be developed and marketed.

Fisheries research in Uganda

Evolution of fisheries research and FIRRI The earliest approach to fisheries research in Uganda dates from the first fisheries survey of Lake Victoria by Michael Graham between 1927 and 1928 (Graham, 1929). Based on references to the rich fisheries that were reported to Graham, it appears that during the 18th Century, catch per net per night averaged 300 tilapia, a revelation that led Graham to conclude that Lake Victoria is a tilapia lake. The "tilapia" later came to be known as Tilapia esculenta and T variabilis (Oreochromis esculentus and O. variabilis) respectively.

Geographic and economic setting of Lake Victoria

Lake Victoria, besides being the second largest in the world after Lake Superior, is the largest tropical lake. Its waters are shared by Kenya (6% of the surface area), Uganda (43%), and Tanzania (51%). Before dramatic structural and functional changes manifested in the lake's ecosystem especially in the 1980s, fish life flourished in the lake's entire water column at all times of the year. Currently, the situation is much more different from what it was in the past. The exponential increase in the introduced Nile perch (Lates niloticus) and Nile tilapia (Oreochromis niloticus) stocks, siltation, wetland degradation and eutrophication have characterised the lake ecosystem. The two exotic species and the small native cyprinid (Rastrineobola argentea) form the basis of the commercial fishery that was once dominated by two native tilapiines (Oreochromis esculentus and Oreochromis variabilis) and five other large-bodied endemic fishes. Severe deoxygenation observed at shallow depths (Ochumba 1990; Hecky et al., 1994) indicates that a large volume of the lake is unable to sustain fish life. The Lake Victoria catchment is one of the most densely populated areas in East Africa, encompassing a population of about 30 million people. Widespread poverty resulting from high inflation rates, lack of opportunities and general unemployment have characterised the lakeside communities over much of the last two decades. The biophysical environment in which Lake Victoria exists makes the lake particularly susceptible to changes that occur as a result of human modification to the watershed or the lake itself, thus rendering benefits from the lake unsustainable.

Composition, biomass, distribution and population structure of the fish stocks

Until the 1970s, Lake Victoria had a multi-species fishery dominated by the tilapiine and haplochromine cichlids. There were important subsidiary fisheries for more than 20 genera of non-cichlid fishes, including catfishes (Bagrus docmak, Clarias gariepinus, Synodontis spp and Schilbe intermedius), the lungfish (Protopterus aethiopicus) and Labeo victorianus) (Kudhongania and Cordone 1974). Stocks of most of these species declined and others disappeared following the introduction of four tilapiines (Oreochromis niloticus, Oreochromis leucostictus, Tilapia rendalli and Tilapia zillit) and Nile perch (Lates niloticus) during the 1950s. Since then the commercial fishery in the Uganda portion of Lake Victoria has been dominated by the Nile perch, Nile tilapia (Oreochromis niloticus) and the native cyprinid species, Rastrineobola argentea (Mukene).

Impacts of fishing gears, fishing methods and fishing effort in the fisheries of Lake Victoria and proposals for management

The initial subsistence fisheries of Lake Victoria were dominated by two indigenous tilapiines, Oreochromis esculentus (Graham 1929) and Oreochromis variabilis Boulenger 1906, exploited with simple fishing crafts and gears that had little impact on the fish stocks (Jackson 1971). Commercial fisheries, targeting the tilapia fishery, started at the beginning of the 20th Centurywhen cotton flax gillnets were first introduced in 1905 into the Nyanza Gulf in Kenya. Gillnets were quickly adopted around the whole lake and consequently, the native methods of fishing soon died out (Jackson 1971). Following the introduction of gillnets, fishing boats and their propulsion methods were also improved. These improvements in fishing capacity coincided with development of urban centres and increasing human population around the lake, which increased the demand for fishery products. To satisfy the increasing demand, fishing effort increased greatly during the 20th century, despite the decline of catch per unit of effort (CPUE) (Jackson 1971; Ogutu-Ohwayo 1990). The initial catch rates of 127mm (5 inch) mesh size gill nets in the tilapia-based fishery, in 1905, was in the range of 50 to 100 fish per gillnet of approximately 50 m in length. However, twenty years later, the catch rates of gillnets of the same mesh size had declined to about six fish per net and gillnets of smaller mesh sizes, which had better catch rates, had been introduced suggesting overfishing (Worthington and Worthington, 1933).

The impact of fishing gears and methods: with recommendations for management of the fisheries of Lakes Victoria, Kyoga and Nabugabo

Historical analysis has shown that use of destructive fishing gears and methods contributed much to the initial depletion of fish stocks from Lakes Victoria and Kyoga. From about 1930 to 1960, the fisheries of Lake Victoria were managed by controlling the mesh size of gill nets. Gill net s of less than 127 mm (5) stretched mesh had been prohibited on Lake Victoria because they cropped immature Oreochromis esculentus (Ngege) which were at that time the most important commercial species. When the mesh size restriction was repealed in the Ugandan, Tanzanian and Kenya, there was a shift to smaller meshes which cropped immature tilapia and other large species and led to a collapse in the fishery.

Farming a new economically viable fish species: Kisinja (Barbus altianalis)

Kisinja (Barbus altianalis)is an indigenous omnivorous fish, of high economic value in Uganda. It was widely distributed in most lakes and rivers in the country but its stocks were depleted due to overfishing and degradation of its natural habitat. 1t can grow up to a maximum length of 120m and a weight of 15kg in the wild and grows faster, attains larger size than commonly farmed fishes in Uganda, including the Nile tilapia, the African catfish, and mirror carp. Kisinja is a highly valuable table fish with good taste and aroma especially when smoked. Increased production of Kisinja is therefore necessary to meet economic and nutritional benefits of the communities and conservation of the spedes.

Manual for production of live feed (Moina) for African catfish fry

The African catfish (Clarias gariepinus) is a commercially farmed fish in Uganda, second in importance after the Nile tilapia (Oreochromis niloticus). This catfish has gained rapid popularity in aquaculture because of its faster growth and higher pond yields attaining average weight of over one kg with pond yields as high as 3.0 kg/m2 in six months compared to an average weight of 500g and pond yields of 1.2 kg.m2 for the Nile tilapia

Invertebrate communitites of lakes Mutanda, Mulehe, Kayumbu and Chahafi and their role in fishery production

Kisoro is a small district (734 km2 ) located in the highland areas of south western Uganda; bordering with Rwanda in the south, Democratic Republic of Congo in the west and Kabale District in the north and the east. The district contains four medium- to- small lakes namely: Mutanda (26.4 km2 ), Mulehe (4.1 km\ Kayumbu (2.2 km2) and Chahafi 1.0 km2). These lakes support small subsistence fisheries for a largely agricultural local population. They are, therefore, locally important as a source of animal (fish) protein, income and employment to the riparian human communities. The fish species include tilapiine fishes: Oreochromis niloticus, 0. leucostictus, Tilapia zillii; Clarias carsoni (Nsonzi), Barbus spp, Cyprinus carpio (Common carp) and the red shrimps

Framework for cage fish culture development in Uganda

This research work involved a review of scientific and technical literature on cage based fish culture technology, and assessment of the natural and socio-economic potential of thiS technology. The research also reviewed secondary data on aquaculture production from the pilot cage culture facilities at Jinja; the requirements of key targeted species for cage based fish production - the Nile tilapia; the feed requirements and implication for management; the physiochemical parameters for optimal performance of fish production in cages; and preliminary production and operational costs of cage fish production.

The effects of trawling on the fish stocks of Lake Victoria

Species composition for Lake Victoria can be divided into two major groups. Haplochromis includes at least four genera, the largest consisting of 120 major species, while the remaining species together number about eighteen. The fish species of this lake have been grouped into two for obvious reasons-Haplochromis forms at least 80 per cent, by weight, of the yield of the lake. When carrying out the survey, the lake was divided into thirteen sampling areas and, although there were variations, all the species were encountered throughout most of the sampling units, except that there were definite trends as one species moved as one from shallow water towards the centre of the lake. It was noted that there was a numerical decrease of species the nearer one got to the centre of the lake, and the catch rates of the species in deeper waters also tended to decrease. The species that were found most consistently throughout the whole lake included Haplochromis complex and Bagrus, and the species found to be confined almost entirely to the shallow waters was Tilapia, in particular Tilapia nilotica.

East African Freshwater Fisheries Research Organization Annual Report 1973

The Annual report presents activities carried out by the Organization during the period 1973. It presents scientific work of the Organization which include: Tissue specificity of malate dehydrogenase in Astatoreochromis and two species of haplochromis, report on LaKe Babati Fishery, Observations on Engraulicypris orgenteus (PELLEGRIN) 1904 from Lake Victoria, Commercial trawl fishing on Lake Victoria: Fisheries development and conservation, Lunar periodicity and the breeding of Tilapia nilotica in the Northern part of Lake Victoria.

A study on stock enhancement/restocking of the Kyoga basin lakes

Increased management attention to the fisheries tn Uganda is fuelled by five major factors:socio-economic demands, human population increase,stock depletion, biodiversity loss and,environmental degradation.Fish exports from Uganda to overseas and regional markets have rapidly increased since the mid 1990s and it is estimated that total exports are worth at least US$ 200m three quarters of the value due mostly to Nile perch exports to overseas markets.Exports to regional markets are dominated by variously processed tilapia "mukene" (Rastrineobo/a argentea),Nile perch "angara"(A/estes baremose) and cat fishes.Virtually all major water bodies contribute to this trade. A combinatilm of exports and an increased human population has seen the per capita fish consumption in Uganda drop from 15kg in the early 1990s to almost 10kg by 2005.this figure is below the WHO recommended fish protein intake of 17kg. the apparent fish gap in a liberalised economic framework has stimulated interest in commercial fish farming