Abstract
Although several papers were dealing with intensively reared broodstocks, most of the published artificial reproduction protocols were applied in wild pikeperch breeders. Therefore, we aimed to evaluate the effects of ovulation induction agents, namely human chorionic gonadotropin (hCG) and salmon gonadotropin–releasing hormone analogue (sGnRHa) on the reproductive performance in pre-seasonal artificial propagation of cultured pikeperch. Breeders were harvested from an outdoor in-pond circulation system in mid-September and transferred to indoor facility in late January, conditioned and injected with either 50 μg kg−1 of sGnRHa or 500 IU kg−1 of hCG, with six females in each hormonal group. Stripped eggs from each female were sampled for chemical composition analysis, fertilised with the milt of two males, incubated and obtained larvae were further reared. No significant differences were noticed between the treatments in any of the analysed parameters of embryo survival nor larviculture performance. Rather high differences in intragroup variation were seen between the treatments, expressed in several-fold higher coefficients of variation in embryo survival in experimental and commercial conditions in the hCG group. Eggs obtained from females treated with hCG had a significantly higher lipid content (31.1% ± 2.0%) compared to sGnRHa-treated females (27.4% ± 1.8%). Fatty acid profiles of the eggs revealed differences in total n − 6 and linoleic acid 18:2n − 6 content while n − 3/n − 6 was significantly lower in the hCG group. Gonadoliberins reduced the variability in the spawning outcome. It appears that hormones can modify the eggs’ fat content during the pre-season artificial reproduction.
Highlights
The issue of producing pikeperch (Sander lucioperca L.) juveniles suitable for intensive ongrowing has gained considerable research attention during the last two decades (Zakęś and Demska-Zakęś 1996; Kestemont et al 2007; Ljubobratović et al 2017a)
Latency time was more variable in the salmon gonadotropin–releasing hormone analogue (sGnRHa) group; the timeframe between the first and last ovulation in the group was 92 h, while in the human chorionic gonadotropin (hCG) group, it took 29 h for all females to ovulate
While the commercial survival and pre-hatch survival in the sGnRHa group was rather stable at 50.2% to 79.3% and 75.6% to 94.4%, respectively, in the hCG, these parameters showed high variability, being in the range of 0% to 69.8% and 0% to 91.3% for commercial and pre-hatch survival, respectively
Summary
The issue of producing pikeperch (Sander lucioperca L.) juveniles suitable for intensive ongrowing has gained considerable research attention during the last two decades (Zakęś and Demska-Zakęś 1996; Kestemont et al 2007; Ljubobratović et al 2017a). Spawning induction of these fish after the grow-out phase has been the subject of a handful of studies far (Hermelink et al 2013, 2017; Zakęś et al 2013) These studies focused on the usage of recirculation aquaculture systems (RASs) for this task with a single study dedicated towards pond wintering of cultured breeders (Ljubobratović et al 2017b). Previous studies have shown that such induced pikeperch breeders could be propagated already in early winter with rather satisfying results in the main parameters of reproductive performance (Zakęś and Szczepkowski 2004; Ronyai 2007; Müller-Belecke and Zienert 2008). These early studies described egg quality parameters in terms of embryo survival and hatching only. The quality of the egg is defined as its competence to develop into a proper embryo (Bobe and Labbé 2010), recent studies found it crucial to incorporate additional parameters for more accurate evaluation of the quality of gametes in percids (reviewed by Schaerlinger and Żarski 2015)
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