Contribution No. 17, SEAFDEC.

Spent Penaeus monodon females were tagged around one eyestalk with numbered brass tags, stocked in a concrete tank with males, and periodically examined for ovarian rematuration over a six-month period (February to August, 1977). The females were either artificially-induced (ablated spawners from concrete tanks and marine pens) or wild spawners. Most of the wild spawners were ablated after spawning; some remained unablated to serve as controls. Out of a total of 349 experimental females, 35 or 10 1% had a second spawning and 5 or 1 4% a third spawning; none of the 74 controls spawned subsequently. The average number of days for maturation and rematuration were: ablation to first spawning, 22 6 days; first spawning to second spawning (for females ablated before the first spawning), 11 days; first spawning to second spawning (for females ablated after the first spawning), 15 days; and second spawning to third spawning, 10 4 days. Fecundity of rematured spawners is comparable to that of first spawners; there is insufficient data on hatching rate and fry survival.