The effects of gonadotropin-releasing hormone analog on yellowtail kingfish Seriola lalandi (Valenciennes, 1833) spawning and egg quality

•We examined the usefulness of GnRHa implant in yellowtail kingfish (Seriola lalandi) to increase the number of contributing parents.•Genotyping showed that GnRHa implant increased number of females contributing eggs.•However, GnRHa implant was associated with reductions in egg quality, likely related to suboptimal timing of implantation.

Communal spawning behaviour in marine aquaculture species often results in a few individuals contributing disproportionate amounts of gametes. This can lead to a reduction in genetic variability and increases the risk of inbreeding among successive generations. Therefore, long term sustainability of captive breeding programmes for such species partly depends upon maintaining a sufficiently high proportion of parents contributing high quality gametes during spawning. The current study was conducted to evaluate if the use of slow-release gonadotropin-releasing hormone analog (GnRHa) implants could increase the number of females spawning high quality gametes, and thus increase genetic variation in a captive population of yellowtail kingfish Seriola lalandi (Valenciennes, 1833). Broodstock fish received implants with or without 500 μg of GnRHa during the spawning season. GnRHa treatment was associated with a higher proportion of females contributing to spawning. However, compared to eggs from non-GnRHa-treated broodstock, GnRHa significantly decreased the floating rate, fertilisation rate, number of viable eggs and egg oil globule diameter. Overall, the use of slow-release GnRHa implants is a useful tool to increase parental contribution to spawning, but this benefit must be carefully balanced against lower egg quality.