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

Objective: 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 whether commercial diets could replace a diet consisting of fresh fishery products (FFP-D) without compromising egg quality and biochemical composition, specifically FAs.Methods: In 2017, one broodstock group (one female and two males) 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 broodfish to spawn repeatedly in a tank, a finding that led to a replicated diet experiment during 2018 in which 18 CYT broodfish were divided into six replicate tanks, with one female and two males per tank. Three tanks were fed the FFP-D as a control, and three tanks were fed a commercial diet (COM-D; Breed-M, INVE). For each spawning event, egg quality metrics were collected, along with samples for FA analysis.Result: The 2017 REF-D treatment produced eggs that met arachidonic acid (ARA) and eicosapentaenoic acid (EPA) requirements and had egg metrics comparable to those obtained from the FFP-D, with higher viability and average batch fecundity. However, the REF-D treatment 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 was associated with very poor spawning and hatch success and had insufficient DHA levels. The FFP-D treatment produced below-average viability and batch fecundity rates and was unable to meet most essential FA requirements, but it yielded the greatest number of spawning events.Conclusion: None of the experimental treatments, including the control, was able to fully meet the nutritional requirements of CYT broodstock. These results reveal crucial data about current CYT broodstock diets that can facilitate future research for developing nutritionally complete diets, especially in terms of essential FAs.