Effects of hormonal treatment before water warming on synchronisation of spawning time, oocyte size, and egg quality...

Inducing reproduction during periods of the year when spawning typically does not occur is an important goal for the feasibility of commercial fish farming. Pre-seasonal propagation of pikeperch generally occurs about 3 months before the natural spawning season. The objective of this study was to assess effects of imposing a thermal schedule for control of water temperature and differing salmon gonadotropin releasing hormone analogue (sGnRHa) dosages on final stages of oocyte growth, and egg quality by optimizing protocol duration and synchronizing spawning time. In Experiment 1, there was analysis of thermal schedule effects for water temperature control when hormonal administrations occurred before or after water warming (WARMING and STABLE, respectively). In Experiment 2, there was assessment of the sGnRHa dosage effects during the warming schedule. In both experiments there was analysis of oocyte diameter from time of sGnRHa administration until the late stages of maturation. There was greater synchrony in time of spawning in specimens of the WARMING group with lesser variability in time from sGnRHa administration to spawning. In Experiment 2, values for reproductive variables were variable among the different groups, without any differences between treatments. Oocyte diameter at the time of sGnRHa administration was correlated with embryo survival. For effective pre-seasonal pikeperch propagation, the selection of breeders based on oocyte diameter, and administration of 5 μg/kg sGnRHa immediately upon transport to hatchery, followed by a 1 °C/d temperature increase to 10 °C, are effective methods for induction of spawning during periods when spawning does not naturally occur.