Individual spawning control in different turbot (Scophthalmus maximus L.) broodstock under artificial and natural photoperiod

As fry output depends highly on management and control of the spawners, this paper examines the results with spawn obtained under a natural and artificial light cycle over a one-year period. The broodstock consisted of 55 females and 69 males, distributed with the same age and sex ratio in 5 tanks. Two of tanks were subjected to controlled photoperiod (group A) and the other three to natural conditions (group B). The spawning period of group A lasted from March until June, and that of group B from May to October. During this period, the spawning sequences of females were monitored individually. The total production of larvae was 2,233,254 larvae, of which 71.72 % were from the tanks with controlled photoperiod. In the fifth tank, fema1es which had not spawned in the previous years were tested, and no 1arvae were produced. This confirmed that the criterion for se1ection was adequate. A mean of 260,933 eggs per Kg of females were obtained, of which 45.56% were of good qua1ity. The mean ferti1ization and hatching indices were 71.40% for group A and 21.99% for group B (not inc1uding tank T-5).0,000