Concepts, alternatives, and environmental considerations in the development and use of improved strains of tilapia in African aquaculture

The status of African populations of farmed tilapia is reviewed and discussed in light of the need for improved strains for commercial aquaculture. Many tilapia populations currently held on African fish farms have been genetically compromised through one or more of the following: inbreeding, negative selection, genetic drift, and unregulated hybridization. Their performance is currently 20–40% lower than the wild populations with which they have been compared and almost 100% less than some improved lines.

Response of two generations of selection to increased body weight in channel catfish, Ictalurus punctatus, compared to hybridization with blue catfish, I. furcatus, Males

Two generations of selection for increased body weight in Kansas (AU-KS-2) and Marion (AU-MS-2) lines of channel catfish, Ictalurus punctatus, resulted in a 12% and 11% increase in body weight at market size, respectively. The second generation of selection produced no improvement in growth, and there was a slight negative response to selection for body weights during the second generation. Cumulative realized h2 was 0.17"0.03 and 0.15"0.03 for AU-KS-2 and AU-MS-2, respectively, based on growth performance measured against a randomly bred, Kansas control for the two generations.

A practical quantitative method to estimate relative reproductive activity in Oreochromis niloticus.

Exact quantitative measurements of reproductive traits such as variation in age and size at maturity, frequency of spawning and their relationship with growth performance require regular draining of ponds and sampling of all individuals, which is impossible to carry out during routine production cycles. The method proposed here attemps to utilize the information on morphological and behavioral changes associated with reproduction that can be routinely recorded during regular random sampling of individuals, to construct a reproduction index.

Management of broodstock and quality control of fish seed in Hungary

Common carp (Cyprinus carpio) breeding has a long tradition in Hungary. However, recent economic changes in Eastern Europe and new developments in aquaculture necessitated the need for ensuring quality of the brood stock used in hatcheries and the legal and institutional frameworks needed to implement the program. In addition to good research and development programs and gene banking, it became essential to establish an appropriate legal framework, organize, coordinate and control breeding activities, and provide financial support.

Tilapias: 'Everyman's fish'

Tilapia culture is in an explosive growth phase and is being supported by increasing R and D efforts. Future possibilities include genetic improvement of growth performance and environmental tolerance in cultured tilapias, and the establishment of accredited breeding centres. Tilapia semen has been stored successfully in liquid nitrogen. Improvements are also anticipated in the use of waste-fed culture systems, such as the production of artificial detritus as cheap supplemental feed.

Genetic improvement of farmed tilapias: growth performance in a complete diallel cross experiment with eight strains of Oreochromis niloticus.

A complete diallel cross experiment was carried out with eight strains of Nile tilapia (Oreochromis niloticus). The strains represented four wild populations collected from various locations in Africa and four populations that had been reproduced over a large number of generations for tilapia farming in Asia.

A review of carp genetic research and possible approaches to genetic improvement of Asian carps.

Currently available information on all aspects of genetics relevant to improving the production efficiency of carpsunder various farming systems is reviewed. With the virtual closure of the life cycle of many of these carps within the culture environments and a rapid increase in artificial propagation, there is a need to monitor scientifically the broodstock management practices and possible genetic changes taking place in the cultured stocks.

Current trends in the Asian tilapia industry and the significance of genetically improved tilapia breeds.

Tilapia production is increasing rapidly in Asia, and is one of the most popular aquaculture activities in PR China, Philippines, Indonesia, Taiwan and Thailand. The most popular farmed tilapia species is still the Nile tilapia (Oreochromis niloticus) cultured in over 40 countries. Tilapia culture is a profitable enterprise and even small farmers can afford to culture tilapia to augment their income. Tilapia is consumed mainly by poor people, as it is relatively low priced.

Performances of Nile Tilapia (Oreochromis niloticus) selected for high growth rate after three generations

A selective breeding study for live weight based on a fully pedigreed population of GIFT (Genetically Improved Farmed Tilapia) strain was carried out at the Aquaculture Extension Centre, Department of Fisheries, Jitra, Kedah. Progeny were generated in three spawning seasons, 2002, 2003 and 2004. Two lines were created from the 2002 progeny, based on high breeding values (selection line) and for average breeding values (control line).


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