The survival, growth, gonadal development and sex ratios of gynogenetic diploid turbot Scophthalmus maximus between 9 and 36 months of age were investigated. Gynogenesis was induced by activation of freshly collected eggs with diluted (1 : 10 with Ringer) and UV‐irradiated (30000 erg mm −2 ) sperm, followed by a cold shock at −1 to 0° C for 25 min, starting at 6·5 min after fertilization. The exclusive maternal inheritance of...

European sea bass Dicentrarchus labrax of the north‐western (NW) and south‐eastern (SE) Mediterranean Sea strains were exposed to different temperatures (13, 17 or 21° C) during the larval rearing (11–51 days post hatching, dph) or nursery periods (55–95 dph), in order to examine the effects of temperature on sex differentiation and subsequent growth during the first year of life. Higher growth was observed during exposure to...

Starting from 66 days post hatching (dph), European sea bass Dicentrarchus labrax were graded successively to create a fast growing (L‐extreme) and a slow growing (S‐extreme) population. The L‐extreme population grew significantly larger (ANOVA, n = 89–101, P v . 66·7 ± 0·9 g, mean ± s . e .). When the two populations were sexed, the L‐extreme consisted of 96·5% and the S‐extreme of 30·2% females, while the ungraded control ha...

Gynogenesis showed little effect on general physiology and gonadal development in sea bass Dicentrarchus labrax . Meiogynogenetic fish showed well‐developed gonads indicating low occurrence of developmental imbalances even after gynogenesis induction in this species. In addition, the proportion of sexes of meiogynogenetic sea bass was similar to the diploid controls in two independent trials, which did not deviate significantl...

Twenty‐day exposures to 17α‐methyltestosterone (MT) (10 mg kg‐© 1 food) starting at 86 or 106 days post fertilization (DPF) resulted in a complete masculinization of sea bass Dicentrarchus labrax , as opposed to 46% females present in the controls. Earlier exposures failed to suppress ovarian development, resulting in a variable number of females (range 10·5–49·5%). All treatments assayed between 110 and 210 DPF induced a comp...

During their 3–4 first years of life, triploid sea bass Dicentrarchus labrax grew in a similar fashion to diploids in fork length but more slowly than diploids ( P 1 kg) sea bass. The condition factor was reduced in both ploidies during the spawning season which took place in winter when the temperature was low. These observations suggest that any growth advantage in triploids, which were functionally sterile, may be offset by...

Groups of sexually undifferentiated sea bass Dicentrarchus labrax were fed with the androgen 17α‐methyltestosterone (MT) during sex differentiation. MT treatment increased males from 79±3% in the controls (the usual 3:1 male:female sex ratio of cultured sea bass) to 100±0%, implying that in the treated groups one out of each five resulting males was a masculinized female (neomale). Thirteen males from the MT treated groups wer...