Abstract
Ichthyoplankton communities provide important information on spawning dynamics and early life-history processes of fish populations. This study investigated the species composition and seasonal occurrence of fish eggs and larvae in Yeongil Bay, in the East Sea of Korea, from January to December 2023. Samples were collected at seven stations and identified based on morphological characteristics and molecular analysis using mitochondrial DNA (COI and 16S rRNA). Thirty-six egg taxa (676 ± 739 eggs 1000 m−3) and 42 larval taxa (28 ± 35 larvae 1000 m−3) were identified. The dominant egg species were Engraulis japonicus (23.3%), Pseudopleuronectes herzensteini (11.8%), and Sardinops sagax (9.8%), while the dominant larval species were Sebastes inermis (29.7%), Sillago japonica (20.7%), and Sebastiscus marmoratus (5.5%). Egg abundance increased from spring and reached a peak in July, whereas larval abundance showed seasonal peaks in January and August. nMDS ordination showed seasonal variation in assemblage structure. Egg assemblages showed seasonal grouping patterns that corresponded with seasonal variation in surface water temperature and salinity, whereas larval assemblages showed relatively more complex seasonal patterns and were characterized by higher species richness and more extended seasonal occurrence. These results suggest that ichthyoplankton assemblages in Yeongil Bay exhibited seasonal variation in species composition during the study period, with E. japonicus eggs comprising the dominant component of the summer ichthyoplankton assemblage. Furthermore, the combined use of morphological and molecular identification improved species-level resolution and provided baseline information for understanding seasonal variation in ichthyoplankton assemblages in this coastal ecosystem.