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In pelagic fish species, studying reproductive behaviour and spawning dynamics is challenging. In culture scenarios, these parameters are difficult to investigate for broadcast spawners such as Seriola. Hubbs‐SeaWorld Research Institute has been culturing California yellowtail (S. dorsalis) since 2003 and now it is poised to become one of the first commercial offshore aquaculture marine finfish species in Southern California. Brood fish are typically kept in large tanks and spawn volitionally throughout the spawning season. This method is successful in yielding a consistent supply of eggs; however, it limits the understanding of spawning group dynamics or individual brood fish contribution, information that will be important to scaling production to commercial levels. In this study, genetic‐based offspring parentage analyses were used to evaluate captive spawning dynamics in S. dorsalis over two consecutive spawning seasons. The analyses determined that typically one female released eggs during a spawning event, compared with an average of six males who released milt during these same spawning events. Notably, the analyses revealed that a single female dominated spawning output in both years, participating in 63 spawning events and producing 49.7 million eggs. The largest single spawn contribution by a female was 2.5 million eggs, corresponding to a batch fecundity estimate of 110,000 eggs kg−1. The spawning interval for the most productive females was 5–6 days. Using genetic tools to characterize spawning events will help to improve breeding programme designs for S. dorsalis, and this information can serve as a proxy for estimating spawning capacities of this species in the wild. [ABSTRACT FROM AUTHOR]

It is likely that Seriola spp. have nutritional requirements for long-chain polyunsaturated fatty acids (LC-PUFAs) and are unable to meet physiological demand for these nutrients via biotransformation of C 18 polyunsaturated fatty acids (C 18 PUFAs). However, it is unclear whether 20:4n-6 (arachidonic acid, ARA), 20:5n-3 (eicosapentaenoic acid, EPA), and 22:6n-3 (docosahexaenoic acid, DHA) are each required or, as in other fish, EPA is comparatively unimportant in maintaining performance of Seriola spp. Accordingly, we assessed growth performance and tissue fatty acid composition of juvenile California Yellowtail Seriola dorsalis (formerly Seriola lalandi ) fed a fish oil-based positive control diet (FISH), a soybean oil-based negative control diet (SOY), or experimental diets based on soybean oil supplemented with ARA, EPA, DHA, ARA and DHA, or all three of these fatty acids combined to achieve 50% or 100% of the concentrations typically observed in fish oil (SOY + 50% ARA, SOY + 100% ARA, SOY + 50% EPA, SOY + 100% EPA, SOY + 50% DHA, SOY + 100% DHA, SOY + 50% ARA and DHA, SOY + 100% ARA and DHA, SOY + 50% ALL, SOY + 100% ALL). As expected, fish fed the SOY diet exhibited significantly reduced growth relative to those fed the FISH diet. Supplementing with ARA alone had no effect on growth performance, and independent supplementation with EPA or DHA did not yield predictably positive effects on growth. However, fish fed the SOY + 100% ARA and DHA feed grew as well as those fed the FISH diet, and those raised on the SOY + 50% ALL and SOY + 100% ALL diets outperformed all others. Fatty acid composition of the fillet, liver, eye, and brain tissues was significantly affected by dietary treatment. As expected peripheral tissues were more modified than central tissues, and tissues of fish fed the soybean oil-based feeds exhibited higher levels of 18:2n-6 and lower levels of LC-PUFAs than those fed the rest of the experimental feeds. This effect was less overt among feeds supplemented with ARA and DHA or all three fatty acids. Results indicate that soybean oil can completely replace fish oil in California Yellowtail diets, assuming adequate levels of DHA and ARA are provided. Furthermore results illustrate the value of supplementing fish oil-free feeds with ARA, EPA, and DHA, but suggest that ARA and DHA are the primary drivers of LC-PUFA essentiality in this species. Statement of relevance The current manuscript provides valuable insights for fish nutritionists, for the aquafeed and aquaculture industries regarding fatty acid essentiality for marine carnivorous finfish. Our study supports the hypothesis that some LC-PUFAs are more physiologically important than others, with DHA and ARA being the primary drivers of fatty acid essentiality for juvenile California Yellowtail. [ABSTRACT FROM AUTHOR]