The 5¢ flanking region (1712 bp) of the growth hormone (GH) gene of the gilthead sea bream Sparus aurata was cloned, sequenced and characterized. It contains a consensus sequence for TATA box and several Pit-1 binding site motifs. Consensus sequences related to cyclic AMP response element, glucocortiocoid response element, and several other transcription factors were identified by comparison to consensus sequences in fish or mammalian GH genes. The promoter contains two microsatellites (di-and tri-nucleotides repeats) with additional upstream microsatellites (triand tetranucleotides), 10-mer tandem repeat, and two long inverted repeats. Analysis of the proximal dinucleotide microsatellite by polymerase chain reaction revealed polymorphism among individuals from a hatchery population and an association of alleles 250 and 254 with growth performance. Segregation analysis of this marker in one family showed Mendelian inheritance. These results suggest that the microsatellite in the promoter region (termed saGHpCA) might be considered as a candidate genetic marker for broodstock management and growth selection programs of Sparus aurata.

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The experiments were designed to evaluate the suitability for mariculture of the diploid and triploid hybrids of gilthead seabream Sparus aurata and red seabream Pagrus major, both of which are members of the Sparidae family. Performance testing of the hybrids was carried out in comparison with the parental species under the same controlled environment. The reciprocal diploid hybrids as well as the triploid hybrid did not exhibit any significant growth advantage over diploid parental species either before or after sexual maturity. The adults, both reciprocal diploid hybrids and triploid hybrid (female S. aurata× male P. major), were clearly immature and had only vestigial gonads; neither ovaries nor released milts were observed. Histological examination of the gonads, carried out during associated periods of the first and second maturation cycles of the parental species, showed that all the hybrids were completely sterile. Despite their sterility, the growth of the hybrids did not display any positive effect, and for this reason their commercial culture appears to be questionable. On the other hand, the use of sterilization through hybridization and chromosome set manipulation may be important when there is a need to restrict the ecological impact on a wild population.

The European sea bass (Dicentrarchus labrax) is one of the most important commercial marine fish species in the Mediterranean basin. However, broodstock domestication and selective breeding on a production scale have yet to be exploited. We reared progeny of sea bass from three different strains and their crosses throughout the entire growth cycle to market size. Data sets were analyzed to assess whether culture performance differs among different strains and crosses reared under controlled laboratory conditions using both separate and communal rearing techniques. Strains and crosses of sea bass varied significantly for traits of economic interest such as growth, survival, body composition, sex ratio, sexual maturation patterns of males, and frequencies of body shape abnormalities. Lack of evidence for substantial heterosis for growth among reciprocal crosses was also detected. Significant sexual dimorphism for length and weight was evident in all strains and crosses. At market size, the resulting weight advantages of females varied between strains and crosses; overall average weight advantage for females was about 39%. Length and weight of individual fish were strongly correlated during different time intervals. This may be useful for the choice of selection criteria, raising the possibility that the response to selection for weight at market time may be achieved by conducting selection on young fish. Generally, the results showed a high culture potential of sea bass strains originating from the southeastern areas of the Mediterranean Sea, suggesting that these domesticated strains can be exploited in future selective breeding programs.

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