Spawning frequency and quality of harem (1 male, 2 females) and pair groups of Centropyge aurantonotus were evaluated. 4 pairs and 1 harem were successfully formed, while a second harem failed to establish. Breeders (Females: TL 4.6±0.2 cm; Males: TL 6.0±0.4 cm) were maintained in 400 L cylindrical tanks (27±1°C; 34 ppt; 14 h photoperiod) with 5 shelters and fed 4 times daily (commercial feed/seafood mix). Spawning was monitored over 52 days from September 2024 to July 2025 (6 in spring, 17 summer, 19 autumn, 10 winter). Of these, 21% were full moon, 29% waning, 17% waxing, and 33% new moon.
Spawning frequency varied among groups, showing no consistent seasonal pattern (Fig. 1A). Harems showed a markedly higher spawning consistency (80–100%) than pairs (10–100%), suggesting social structure plays a key role in reproductive output. The lower frequency in pair 1 may relate to advanced male age. No effect of lunar phase was found on spawning (p = 0.12), with all groups spawning at similar frequencies (21–39%). During a 7-day summer evaluation, total egg production (Fig. 1B) and hatching rate (Fig. 1C) were significantly higher in the harem group compared to pairs (p<0.01), reinforcing the potential of harems for more frequent and productive spawning in captivity. Further studies are needed to investigate year-round reproductive performance and the effects of environmental and biological factors on egg viability and larval success.
The use of harem structures appears to be a promising strategy for enhancing C. aurantonotus reproductive efficiency in captivity.