We investigated the seasonal occurrence pattern among Acartia species in Gamak Bay, Southern Korea by comparing their biweekly abundance from April 2020 to April 2021 with their egg production rate (EPR) and hatching success (HS). The five Acartia species showed clear seasonal succession. Acartia omorii and Acartia hudsonica occurred mainly during the cold season and disappeared in summer, whereas A . erythraea , A . sinjiensis , and A . ohtsukai showed the opposite pattern and co-occurred during the warm season. Peak abundances of the warm-season species were mainly associated with water temperature and salinity. EPR ranged from 1.5 to 26.7 eggs female -1 day -1 , and mean HS was lower in the cold-season species than in the warm season species. Eggs of the warm season species hatched rapidly, mostly within 72 h, whereas those of the cold-season species often showed delayed hatching, extending to 120 h. These differences in reproductive timing and hatching phenology suggest species-specific seasonal strategies among co-occurring Acartia species. Our results indicate that hydrographic seasonality, together with species-specific reproductive characteristics, helps explain the annual succession of Acartia populations in this semi-enclosed coastal embayment, and may also provide insight into similar succession patterns in other semi-enclosed or hydrographically dynamic coastal systems.
Lee et al. (Fri,) studied this question.