Pioneering fish genetic resource management and seed dissemination programmes for Africa: adapting principles of selective breeding to the improvement of aquaculture in the Volta Basin and surrounding areas

This document represents the report and contributed papers from a workshop of the same name. The workshop was comprised of a group of 30 international experts and representatives of the environmental, fisheries and policy development agencies of the countries in the Volta Basin.

Pawpaw seed as fertility control agent on male Nile tilapia

To find out if pawpaw (Carica papaya) seeds can induce sterility in male Nile tilapia (Oreochromis niloticus) and to determine if sterility so induced is reversible or otherwise, mature male tilapia of mean weight 40 g were treated for 30 days with a low dose (4.9 g/kg/day) and a high dose (9.8 g/kg/day) of ground pawpaw seeds incorporated into their feed. Fish of similar sizes in the control experiment were fed with feed that did not contain pawpaw seed.

Opportunities and challenges for African aquaculture

Starting from a small base, aquaculture production in Africa registered annual growth rates equal to or above those in other regions. This expansion was due to significant increases in a few African countries. Increasing demand coupled with rapidly dwindling catches from capture fisheries, the implementation of novel participatory approaches to technology development and transfer, and the emergence of a few successful large-scale tilapia culture operations directed at the export market offer opportunities for further expansion in both the small-scale and large-scale commercial sectors.

On-farm and on-station comparison of wild and domesticated Cameroonian populations of Oreochromis niloticus

Wild (Sanaga River) and domesticated populations of Oreochromis niloticus were compared onfarm and on-station in the Central Province of Cameroon to determine the degree to which genetic deterioration of stocks may have occurred during the process of domestication and subsequent breeding. On-station, average weight at harvest was 284.3 ± 16.2 and 178.1 ± 9.9 g for Sanaga and domesticated populations, respectively. On-station specific growth rate was 0.0660 ± 0.0022 and 0.0555 ± 0.0016 g/day for Sanaga and domesticated populations, respectively.

Mass spawning of Oreochromis niloticus for fry production: threats and opportunities for small-scale aquaculture and selective breeding

Mass selection based on mass spawning can present a feasible and low-cost selective breeding scheme. In mass spawning, however, mating is not controlled and a small number of breeding individuals may account for a lafgeproportion of the next geperation, leading to higher inbreeding, decrease in performance of stocks and no response to selection: To understand the mating systems, reproductive and population parameters under mass spawning, we conducted mass spawnings with female to male sex ratios of 1:1,2:1 and 3:1.

Investment Appraisal of Genetic Improvement Programs in Nile tilapia (Oreochromis Niloticus)

The economic benefit derived from a genetic improvement program with Nile tilapia (Oreochromis niloticus) was examined from a national perspective. An industry structure was assumed whereby the genetic improvement program is conducted in a nucleus which provides brood stock to hatcheries, which in turn produce fry for farmers to grow out to market size. Discounting was used to express all returns and costs in terms of net present value. The economic benefit (discounted returns minus discounted costs, EB) and the benefit/cost ratio (BCR) were studied for a 10 year time horizon.

GIFT technology manual: an aid to tilapia selective breeding

This manual is intended as an aid in the transfer of the selective breeding technology developed by the WorldFish Center and its partners. It was based upon experience and material accumulated during the ‘Genetic Improvement of Farmed Tilapia’ (GIFT) project (1988 to 1997). In its development particular attention was paid to the description of key husbandry operations in a sequential manner, using illustrations and photographs. There will be, however, instances in which some adjustment of the GIFT technology to local conditions is required.

Genetic parameter and genotype by environment interaction for body weight of Oreochromis shiranus

Genetic and phenotypic parameter estimates for tagging and harvest body weights were obtained from the F1 base (377 offspring of 59 full-sib families), F2 (1241 offspring of 52 full- and 33 half-sib families) and F3 (1052 offspring of 55 full- and 25 half-sib families) generations of Oreochromis shiranus. The fish were reared in earthen ponds at three different test environments inMalawi, which were high altitude (Chisitu), medium altitude (Domasi) and low altitude (Kasinthula) fish farms.

Genetic improvement with specific reference to tilapia genetic resources in Africa and their use in aquaculture - potential benefits and risks.

In comparison to the rest of the world, aquaculture in Africa is fairly insignificant. The continent as a whole contributed a mere 0.9 per cent (404 571 t) to the total world aquaculture production in 2000. The African continent, however, exhibits considerable potential in terms of land and water and in regard to inland, coastal and offshore resources. Genetic improvement of tilapias has a role to play in order to increase aquaculture production.

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