Induced ovulation of Southern flounder Paralichthys lethostigma using gonadotropin releasing hormone analogue implants

Implanted pellets that provide a sustained release of [D-Ala(6)Des-Gly(10)] LHRH-ethylamide (GnRHa) were used to induce maturation and ovulation of Southern flounder Paralichthys lethostigma. Of the 12 females whose ovaries contained follicles with a maximum diameter greater than or equal to 500 mu m, 11 ovulated for the first time within 90 h of hormone implantation, Only 1 fish with a maximum follicle diameter less than 500 mu m ovulated within 2 wk after implantation, Ovulated eggs were manually stripped from the females and mixed with sperm from several males, Most females were spawned 1 to 3 times on consecutive days with variable fertility, One female was spawned 11 times producing 668,000 eggs, Fertility was evaluated by examining the incubated eggs for early stages of embryonic cleavage, The percentage of fertile eggs in subsamples of incubated eggs ranged from 7-95%, The results indicate that GnRHa implants can be used to induce repeated ovulation in this species, The variability in fertility is discussed in relation to egg quality.