Risk analysis in aquaculture: A step-by-step introduction with worked examples

This publication is based on materials covered and outputs generated during the Workshop on Risk Assessment Methodologies and Tools for Aquaculture in Sub-Saharan Africa, which was jointly held by WorldFish and FAO in Siavonga, Zambia on 28 June - 2 July 2010. The workshop was delivered as a training exercise to 17 participants from seven sub-Saharan countries and was designed to highlight current methodologies and tools available for environmental risk analysis in aquaculture development.

Response to selection for growth in an interspecific hybrid between Oreochromis mossambicus and O. niloticus in two distinct environments

The development of a saline tolerant tilapia strain able to grow fast is of importance in the Philippines, where 240 000 ha of brackish water ponds are available. To this end, founder hybridization between Oreochromis niloticus (with favorable growth traits) and O. mossambicus (with favorable salinity tolerance traits) was performed and followed by backcrossing with O. mossambicus to develop a strain highly tolerant to saline environments. Genetic selection for growth performance was subsequently conducted.

Relative performance of two Nile tilapia (Oreochromis niloticus Linnaeus) strains in Egypt: The Abbassa selection line and the Kafr El Sheikh commercial strain

The Abbassa selection line (developed by selective breeding) and the Kafr El Sheikh commercial strain (widely used in Egypt), both Oreochromis niloticus, were compared at two stocking densities (two and four fish m-2). Harvest weight, length, depth, width and head length were recorded. The Abbassa line showed a superior harvest weight (28 per cent) over the Kafr El Sheikh strain. Males were heavier than females, but the between-sex difference was greater in the commercial than in the Abbassa line (39 and 31 per cent respectively).

Quantitative genetic parameter estimates for body and carcass traits in a cultured stock of giant freshwater prawn (Macrobrachium rosenbergii) selected for harvest weight in Vietnam

Benefits derived from selective breeding have been demonstrated in livestock and in some fish species, but by contrast, there have been few systematic selection programs reported for shrimps. Improving growth rate has been identified as the most important trait in the breeding objective for cultured shrimp species. In the present study we analyzed a four generation data set from a fully pedigreed selective breeding program for giant freshwater prawn (GFP in Vietnam. We estimated phenotypic and genetic parameters for body and carcass weight traits.

Performance of the Genetically Improved Farmed Tilapia (GIFT) strain over ten generations of selection in Malaysia

A selection programme using Best Linear Unbiased Prediction (BLUP) method for the estimation of genetic merit was implemented by the Department of Fisheries Malaysia (DOF) in collaboration with the WorldFish Centre. This collaborative programme provided opportunities for further improvement of the GIFT strain in Malaysia. The overall aim of the present study was to evaluate the performance of GIFT strain during the long-term selection programme in Malaysia.

Individual growth monitoring of European sea bass larvae by image analysis and microsatellite genotyping

The aims of the present study were to develop non-lethal methods to identify individual fish larvae and post-larvae before tagging and accurately follow their growth characteristics. European sea bass (Dicentrarchus labrax) was used as a model species at four different ages ranging from 71 to 100 days post fertilization (dpf).

Genetically Improved Farmed Tilapia (GIFT)

Genetic improvement through selective breeding has been used for millennia on crops and livestock, but up until the 1980s, little had been done to utilize this process for farmed fish. In response to the inadequate supply of tilapia seed and the deteriorating performance of the fish in many aquaculture systems in Asia, WorldFish and partners began the Genetic Improvement of Farmed Tilapia (GIFT) project to develop a faster-growing strain of Nile tilapia (Oreochromis niloticus) that was suitable for both small-scale and commercial aquaculture.

Genetic improvement of Israeli blue (Jordan) tilapia, Oreochromis aureus (Steindachner), through selective breeding for harvest weight

Genetic parameters and selection responses were obtained for harvest body weight of blue tilapia (Oreochromis aureus) from data collected over three generations in a selected population. A total of 18 194 records representing 186 sires and 201 dams were used in the analysis. Within generation heritability estimates for harvest body weight ranged from 0.18 to 0.58. When data from more than one generation were included in the analysis, heritability estimates became more stable (0.33–0.40) and it was 0.33 when all data were included in the analysis.

Genetic considerations on acquisition and maintenance of reference populations of tilapia

The maintenance of reference populations of Tilapia is discussed, examining genetic considerations to be taken into account to conserve the gene pool to prevent genetic drift and prevent detrimental levels of inbreeding. The importance of knowledge of the proper effective breeding number and its use in management of the reference population is described.

Considerations about effective dissemination of improved fish strains (in Arabic)

Aquaculture production systems in developing countries are largely based on the use of unimproved species and strains. As knowledge and experience are accumulated in relation to the management, feeding and animal health issues of such production systems, the availability of genetically more productive stock becomes imperative in order to more effectively use resources. For instance, there is little point in providing ideal water conditions and optimum feed quality to fish that do not have the potential to grow faster and to be harvested on time, providing a product of the desired quality.


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