Effects of GnRHa and pimozide treatments on the timing of ovulation and on egg quality in arctic charr (Salvelinus alpinus) at 5 and 10øC. ; Effet de traitements au GnRHa et au pimozide sur le rythme des ovulations et la qualité des œufs chez l'omble chevalier (Salvelinus alpinus) à 5 et 10 °C

International audience ; The effectiveness of different gonadotropin releasing hormone analogues (GnRHa) and/or pimozide for inducing ovulation in Arctic charr was investigated at two different temperatures : 5 degrees C, a temperature suitable for spontaneous ovulation in Arctic charr and 10 degrees C, a temperature which inhibited ovulation in Arctic charr. At 5 degrees C all the different GnRH analogues tested were able to induce and synchronize ovulation. At 10 degrees C a sustained release preparation of D-tryptophan(6) luteinizing hormone releasing hormone (D-Trp(6)LH-RH) at 20 mu g.kg(-1) and an acute release preparation of D-arginine(6)salmon GnRH (D-Arg(6) sGnRH) at 100 mu g.kg(-1) were able to induce ovulation in 80% of the females within 15 days (versus 2% in controls). Pimozide alone or in combination with a low dose of D-Arg(6)sGnRH was able to induce some ovulation at 10 degrees C, suggesting that a dopamine inhibition of gonadotropin secretion could occur at 10 degrees C. Egg survival in groups receiving GnRHa at 5 degrees C was comparable to controls (73%) except in the group receiving GnRHa in combination with pimozide (45%). At 10 degrees C, egg survival was significantly lower than controls at 5 degrees C, except for the group receiving pimozide alone. At both temperatures, egg survivals of each spawn were negatively correlated with the plasma gonadotropin (GtH2) level of the reproducing females except in groups receiving a sustained release preparation of D-Trp(6)LH-RH. ; L'efficacité de différents analogues du GnRH et/ou du pimozide pour induire l'ovulation chez l'omble chevalier est étudié à deux températures : 5 °C, une température propice pour l'ovulation spontanée de l'omble chevalier et 10 °C, une température inhibant l'ovulation chez l'omble chevalier. A 5 °C tous les différents analogues du GnRH étudiés sont capables d'induire et de synchroniser les ovulations. A 10 °C, une préparation à diffusion prolongée du D-Trp6LH-RH à 20 μg.kg−1 et une forme à diffusion instantanée du ...