Spawning dynamics and egg production characteristics of captive Seriola dorsalis assessed using parentage analyses

Abstract

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.

The status of California yellowtail Seriola dorsalis as a commercially ready species for marine U.S. aquaculture

“…Although recent HSWRI research has demonstrated that small groups of one female and two males will spawn volitionally, male to female ratios in production-scale broodstock tanks are typically at or near 1:1 in groups containing as many as 37 individuals. Recent advances in microsatellite-based parentage analysis research have enabled HSWRI scientists to learn more about which fish within groups are contributing to each spawning event (Schmidt, Hyde, Purcell, & Drawbridge, 2021;Stuart & Drawbridge, 2013). Results from this work have shown that CYT exhibit lottery polygyny spawning dynamics in which only a small proportion of females contribute to spawning while the majority of males contribute to all spawns (Schmidt et al, 2021).…”

“…When held at ambient temperatures and photoperiods in San Diego, California, CYT broodstock typically begin volitional spawning in March when water temperatures are between 14 and 16 C and continue until August or September when temperatures can reach as high as 22 C. Although parentage analysis has shown that an individual female is capable of spawning as often as every other day, the average time between spawns for an established group can range between 11 and 20 days depending on age, size, health, time in captivity, and fish hierarchies (Schmidt et al, 2021). Once mature and well established in groups, females have exhibited mean batch fecundities of 240,000-460,000 eggs per spawn and mean annual fecundities of 3.3-8.2 million eggs per female per year (Schmidt et al, 2021). Captive bred broodstock generally reach sexual maturity at around 24 months, but typically do not exhibit dependable high-quality egg production until at least 3-4 years of age (approximately 4-5 kg).…”

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

“…Studies like these, along with other broodstock diet studies, have shown that the lipid composition of eggs is directly correlated and influenced by the lipid composition of the broodstock diet (Watanabe et al 1984a(Watanabe et al , 1984bMourente and Odriozola 1990;Harel et al 1994;Almansa et al 1999). This influence of dietary lipids is especially evident in CYT because they are continuous synchronous spawners, exhibiting a prolonged spawning season from March to September (Schmidt et al 2021). Unlike asynchronous spawners, CYT spawn multiple times per season and immediately transfer nutrients from their diet into their eggs through a short vitellogenic period (Izquierdo et al 2001).…”

“…This influence of dietary lipids is especially evident in CYT because they are continuous synchronous spawners, exhibiting a prolonged spawning season from March to September (Schmidt et al. 2021). Unlike asynchronous spawners, CYT spawn multiple times per season and immediately transfer nutrients from their diet into their eggs through a short vitellogenic period (Izquierdo et al.…”