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Genetic improvement of fish uses many techniques, from chromosome set manipulations to crossbreeding, selective breeding and transgenesis. Chromosome set manipulations are well described in many species, and are used mainly for sterility (triploids) and for producing monosex populations (gynogenesis, androgenesis). The possibility to obtain inbred clonal lines exists in several species and has potential interesting applications but is not being currently used in practice. Transgenesis offers potential for creating new genotypes, but causes potential risks to the environment, and is rejected by the consumers, and therefore is not used.

 Selective breeding is interesting in fish because it can provide cumulative genetic gains over generations, which can be high due to the high selection intensities that can be applied in prolific species like fish. Basically, three types of methods may be used: methods using individual performances only (mass or individual selection), methods using family information (family, combined, genealogical selection), and methods using marker information (Marker Assisted Selection). Mass selection is relatively cheap and allows rapid progress on simple traits, but indirect criteria are needed for improving lethal traits (e.g. fillet yield, fat content). Family based methods allow selection on multi-trait indexes, but are constrained by the cost of family information, which may be obtained by separate rearing of progenies until tagging size or by DNA fingerprinting. The relative merits of both methods will be analysed. Finally, marker-assisted selection is not yet applied but offers interesting potential for selecting on criteria for which phenotyping is difficult. Different uses of markers in selection will be discussed.

Marc Vandeputte is an agronomist from Paris-Grignon Agronomy School, and has both a MSc in Aquaculture Biology and a MSc in Quantitative Genetics. After various experiences in fisheries and aquaculture development in France and Africa, he joined INRA (National Institute for Agricultural Research) in 1996, and is the Head of the Fish Genetics Laboratory from 2000. He works on selective breeding of  trout, carp, seabass and shrimp.

Contact details: e-mail: mvande@diamant.jouy.inra.fr