INDUCTION OF SPAWNING IN TURBOT (SCOPHTHALMUS-MAXIMUS L) BY A SUDDEN CHANGE IN THE PHOTOPERIOD

Between 1987 and 1988, a broodstock of 17 females and 26 males in two 25 m3 tanks was subjected to controlled photoperiods. Fish were first exposed to a constant photoperiod of 8 h of light per day, and subsequently a sudden change to 16 h of light per day was produced from one day to the next. After two months most of the females ripened and spawned, and all the males produced milt in the same period. Consequently, high percentages of fertilization and hatching were obtained. Methods of controlling the spawning of turbot are discussed, and a quality criteria for turbot eggs is stated in this paper.