EFFECTS OF GNRHA AND PIMOZIDE TREATMENTS ON THE TIMING OF OVULATION AND ON EGG QUALITY IN ARCTIC CHARR (SALVELINUS-ALPINUS) AT 5 AND 10-DEGREES-C

The effectiveness of different gonadotropin releasing hormone analogue s (GnRHa) and/or pimozide for inducing ovulation in Arctic charr was i nvestigated 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 sync hronize 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)sal mon GnRH (D-Arg(6) sGnRH) at 100 mu g.kg(-1) were able to induce ovula tion in 80% of the females within 15 days (versus 2% in controls). Pim ozide alone or in combination with a low dose of D-Arg(6)sGnRH was abl e 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 c ontrols (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 negative ly correlated with the plasma gonadotropin (GtH2) level of the reprodu cing females except in groups receiving a sustained release preparatio n of D-Trp(6)LH-RH.