ASPECTS OF REPRODUCTIVE-BIOLOGY OF THE MEDITERRANEAN AMBERJACK (SERIOLA-DUMERILII RISSO) DURING THE SPAWNING PERIOD

Wild Seriola dumerilii were collected in the South Mediterranean Sea d uring the 1990, 1991 and 1992 spawning seasons. Macroscopic and cytolo gical characteristics of ovary and testis were analysed. Depending on the presence and the number of oocytes at different stages, a five poi nt maturity scale was proposed for ovarian maturity. Nine maturity sta ges of the oocytes are described. Oocyte size-frequency distribution h as shown a group synchronous ovarian development type. The testes have a typical lobular-type structure. Depending on lobules and sperm duct development and on the abundance of germ cells, testis maturity was c lassified in four stages. Maturity race according to age and size was also determined. 100% of 1-year-old fish show immature gonads. The pro portion di females with mature ovaries was 0, 12.5, 84.6 and 100 % at the age of 2, 3, 4 and 5 years respectively. The proportion of males w ith mature testes was 14.3, 40, 80 and 100 at the same age. The median standard length at which 50 % of the fish attained maturity is 109 an d 113 cm SL in males and females respectively.