SEXUAL DIMORPHISM IN GROWTH AND MATURATION OF TURBOT, SCOPHTHALMUS-MAXIMUS (RAFINESQUE, 1810)

Sexual dimorphism in growth and maturation of individually tagged turb ot (n = 421), Scophthalmus maximus Rafinesque, was studied in a long-l asting (20 months) growth experiment with four temperature regimes. Th e influence of onset of puberty and subsequent maturation on growth wa s evaluated. There were no initial size differences, but the final wei ght of females was larger than that of males at all temperature regime s, except at the lowest temperature. Surplus energy (sum of increase i n somatic weight and gonad weight) in females was on average greater t han in males from 8 months prior to first spawning. Significant growth (as specific growth rate, SGR) differences between maturing and immat ure fish were detected from the age of 9 months post hatch. Maturing f emales had the highest growth rate and reached the largest size (1.8 k g in 20 months), whereas male body weights reached a plateau and level led off around 1.0 kg. To optimize production characteristics in turbo t aquaculture and achieve more homogeneous growth, methods should be d eveloped to produce all-female broods.