Egg quality of an Asian catfish of the Mekong river (Pangasius hypophthalmus) during the process of maturation induced by hCG injections

In captive Pangasius hypophthalmus, oocyte maturation and ovulation are induced by hormonal injection following a given protocol: preparatory injections (500 VI.kg-) and decisive injection (2000 VI.kg-). The aim ofthis work is to specify the timing of ovulation and the effects of varying latency period on the quality of ova. Oocytes and ova were collected by intra-ovarian biopsy and hand stripping. Ova quality was estimated by fertilisation rate, hatching rate and proportion of deformed larvae. Ovulation occurred as a synchronous process 8h30 to 9h30 after the last hormonal injection. The first ova obtained (8h30 after injection) were of good quality (85% hatching). At this time, the ovulation rate was 100010. Three hours after ovulation, ageing of ova started to occur: the proportion of deformed larvae increased (24%) and hatching rate collapsed (35%). In P. hypophthalmus, the optimised latency period was found to be 8h30 and corresponded approximately to the completion of ovulation