Comparison of methods to improve induction of spermiation in wild-caught carp (Cyprinus carpio carpio), a threatened species from the Caspian Sea basin

Wild carp (Cyprinus carpio carpio) forms the basis of an important fishery in the Southern Caspian Sea Basin which is increasingly underpinned by the release of cultured juveniles. A significant bottleneck to hatchery-rearing of juveniles is the spermiation of male broodstock. Therefore, four approaches to improving spermiation were investigated. The effectiveness of two delivery methods for the sustained release of salmon gonadotropin releasing hormone analogue (sGnRHa; i.e., via intramuscular cholesterol pellet vs emulsion injection) on the spermiation success and duration, sperm quality and quantity over 14 days in wild-caught carp were compared to single injection of sGnRHa with Pimozide® (Linpe method) or carp pituitary extract (CPE). The consequence of the spermiation treatments on resulting embryonic quality was evaluated for subsequent fertilization and hatching success from wild male carp (mean weight ± S.D. 1021 ± 112 g). All hormonal treatments, except for Linpe method, led to 100% spermiation of treated fish compared to only 25% in the control with no hormone intervention. The duration of spermiation, as well as the various quantitative variables of the sperm and the mean total sperm production were all generally improved with the sustained hormone delivery compared with the acute treatments. The GnRHa-FIA was the most effective method for improving spermiation.