Induction and synchronisation of spawning in cultivated turbot (Scophthalmus maximus L.) broodstock by implantation of a sustained-release GnRH-a pellet

Cultivated turbot were successfully spawned using sustained-release pellets containing a gonadotropin-releasing hormone analogue (GnRH-a), [D-Ala(6)-P ro(9)-Net]-luteinising hormone releasing hormone. Significant synchronisati on of females was obtained, reducing the spawning season by about half. The number of spawning females was increased, and all sexually mature females ovulated. The delay between ovulations decreased from more than 2 days in c ontrols to about 36 h in GnRH-a treated fish. The mean batch volume increas ed from 144 to 214 mi, but total volume of eggs for the whole spawning seas on did not change. At a production scale, fertilisation rate was significan tly lower in the GnRH-a group than in the control (76.6 and 89.5%, respecti vely). Hatching rates were not significantly different between experimental groups. (C) 2000 Elsevier Science B.V, All rights reserved.