Influence of broodstock nutrition on egg quality and fatty acid composition in California Yellowtail

Abstract

California yellowtail (CYT; Seriola dorsalis) are continuous spawners and rely entirely on their diet to supply nutrients like fatty acids (FAs) to their eggs to support early development. The objective of this study was to determine if commercial diets can replace fresh fishery products (FFP‐D) without compromising egg quality and biochemical composition, specifically FAs. In 2017, one group (1 female and two males) of broodstock was fed a formulated reference feed (REF‐D; Bio‐Oregon). This pilot experiment showed that it was possible for a minimum of one female and two male broodstock to spawn repeatedly in a tank which led to a replicated diet experiment in 2018 where 18 yellowtail broodstock were divided into six replicates tanks, with 1 female and 2 males per tank. Three tanks were fed a FFP‐D control and three tanks were fed a commercial diet (COM‐D; Breed‐M, INVE). For each spawn event, egg quality metrics were collected along with samples for FA analysis. The 2017 REF‐D treatment produced eggs that met arachidonic acid (ARA) and eicosapentaenoic acid (EPA) requirements and had comparable egg metric parameters as FFP‐D with higher viability and average batch fecundity. However, it had insufficient docosahexaenoic acid (DHA) and no tank replicates. The 2018 COM‐D treatment produced eggs with large egg and oil diameters and met ARA and EPA requirements but had very poor spawn and hatch success with insufficient DHA levels. The FFP‐D treatment produced below average viability and batch fecundity rates and was unable to meet most EFA requirements, but it yielded the greatest number of spawns events. None of the experimental treatments including the control were able to fully meet nutritional requirements of CYT broodstock. These results reveal crucial data about current CYT broodstock diets that would facilitate future research of developing nutritionally complete diets especially in terms of EFAs.