Here we describe the first documented photothermal spawning control of California yellowtail ( CYT; Seriola dorsalis ) broodstock . Over one spawning season we tracked two groups of F1 generation broodstock and recorded metrics for spawns (egg production, viability), eggs (egg diameter, oil diameter, percent oil volume, hatch rates), and larvae (notochord length at hatch, survival to first feeding). Spawning Group 1 was comprised of two females (16.0 ± 0.1 kg) and five males (15.4 ± 2.4 ) that were held under ambient light and temperature and produced eggs from March through October . Spawning Group 2 was also comprised of two females (12.8 ± 3.1 kg) and five males (12.7 ± 2.2 kg) that were photothermally shifted to spawn from October through April.
The majority of spawning occurred between 13-14 hr of daylight and water temperatures between 15 – 21° C. Group 1 spawned 47 times , producing 22 million eggs and 486,873 eggs per spawn (Table 1). Group 2 spawned less (n= 34) and had lower egg production (20 million eggs), but the eggs per spawn was higher at 604,825 (Table 1) . E gg quality was similar between both groups. W e showed that spawning of CYT can be photothermally controlled with no impacts on egg production or egg quality.