Evaluation of cGnRH IIa for induction spawning of two ornamental Synodontis species

Efficacy, reliability, and safety are of principal concern for spawning aids used in reproduction protocols for aquaculture species. Ovaprim®, a salmon gonadotropin releasing hormone analog (sGnRH IIIa, D-Arg6-Pro9-Net, 20 μg/mL) and a dopamine antagonist (Domperidone, 10 mg/mL), is currently the preferred choice for induction spawning of ornamental fishes. However, this preparation may be unreliable or completely ineffective in some cases. cGnRH IIa (D-Arg6, Pro9-NHet) has garnered recent interest as an alternative GnRH subtype which offers increased biological activity, reliability, and may ultimately help to increase on farm productivity and expand the diversity of species able to be cultured. The objective of this study was to evaluate the efficacy of cGnRH IIa and Ovaprim® on various quantitative and qualitative measures of spawning performance in Synodontis nigriventris and Synodontis eupterus. Four hormone doses were evaluated (50, 100, 200 μg/kg cGnRH IIa; 10 μg/kg sGnRH IIIa), each of which also contained an equal concentration of a dopamine antagonist (5 mg/kg domperidone). Fish were palpated to check for ovulation at 16, 20, and 24 h post injection. Upon successful ovulation, eggs were manually stripped, weighed, and fertilized. A subsample was photographed under a dissecting microscope for subsequent determination of fertilization success and egg diameter. Hatching success for individual spawns was calculated from subsamples of fertilized eggs stocked into hatching containers. Results indicated similar ovulation success among the four hormone treatments at the 16, 20, and 24 h time periods. Total fecundity, fertilization, embryo diameter, hatching success, larval notochord length, and larval mortality did not vary significantly among treatments. These results suggest that cGnRH IIa exhibits comparable spawning performance to the industry standard Ovaprim®, for induced spawning of S. nigriventris and S. eupterus. •We evaluate the effect of Ovaprim and cGnRH IIa on egg and larval quality in Synodontis spp.•Ovaprim and cGnRH IIa are effective at FOM, ovulation, and spawning in Synodontis spp.•The 100 μg/kg cGnRH IIa + 5 mg/kg domperidone treatment can be recommended for spawning applications with these species