The history and current status of aquaculture genetics in Israel.
A review. Genetic improvement efforts in Israel have focused mainly on common carp (Cyprinus carpio) and tilapias and (only recently) on marine fish species. The breeding programme for carp started in the late 1950s and concentrated on growth rate under different culture practices. Originally, the main approach was mass selection, but when this failed to produce results, efforts shifted to evaluating inbreeding and crossbreeding (resulting in wide commercial use of an F1 cross). Chromosome set manipulation has become the major method in recent genetic research in carp, aimed at producing triploid populations and gynogenetic ornamental carp lines. Colour inheritance in ornamental carp is also being investigated. Hybridization among other cyprinids, including grass carp (Ctenopharyngodon idella), bighead carp (Aristichthys nobilis) and crucian carp (Cyprinus auratus), has been examined, but has been found to be of little value for aquaculture. Genetic improvement of tilapias has focused on the all-male interspecific hybrid Nile tilapia (Oreochromis niloticus) × Jordan tilapia (O. aureus). Evaluation of other hybrids did not identify any that is better under Israeli conditions. Sex inversion is also practiced, and current studies are devoted to production of all-male populations by breeding sex-inverted individuals. Other studies involve colour inheritance and the performance of red tilapias and chromosome set manipulation. Since the realized heritability of growth rate in the gilthead sea bream (Sparus aurata) has been estimated to be 0.45, a mass selection programme has been initiated. Preliminary results so far suggest a 20% response in growth rate per generation. Some efforts are being devoted to testing the benefits of crossbreeding and hybridization with Diplodus sargus and red sea bream (Pagrus major). The hybrid was found to be sterile. Chromosome set manipulation aimed at obtaining triploids and gynogenetic (clones) sea bream are also being examined. Genetic engineering efforts are currently directed mainly towards developing methods of producing transgenic carp and gilthead sea bream carrying exogenous somatotropin genes.