울릉도 해역의 어란 및 자치어 종조성과 해양환경 변화에 따른 시·공간적 변동(2021-2024)
Species Composition of Ichthyoplankton and Spatio-Temporal Variations in Relation to Marine Environmental Changes around Ulleungdo (2021- 2024)
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In response to increasing sea surface temperatures and the intensified Tsushima Warm Current in the East Sea, ichthyoplankton were seasonally sampled from 2021 to 2024 around Ulleungdo to assess species composition changes and evaluate spawning and nursery functions. Sampling was conducted at eight stations using bongo and ring nets, and environmental data were recorded with CTD. Fish eggs and larvae were identified morphologically, and COI gene analysis was applied to morphologically ambiguous samples. A total of 37 egg and 48 larval species were identified, with Engraulis japonicus and Maurolicus japonicus dominant in both stages. Cluster and SIMPER analyses revealed interannual variation in eggs and spatial differentiation of larvae after 2023, largely influenced by E. japonicus and M. japonicus. No significant correlation was found with temperature or salinity. However, the increased presence of warm-current larval species in 2023 and 2024, such as Thunnus orientalis, Champsodon snyderi, and Scomber japonicus, coincided with strengthened surface currents, suggesting possible transport from external spawning grounds. The continuous appearance of dominant coastal species supports the role of Ulleungdo as a stable spawning ground, while the irregular occurrence of warm-water species larvae suggests the potential use of the area as a nursery ground under changing oceanographic conditions.
Abstract
In response to increasing sea surface temperatures and the intensified Tsushima Warm Current in the East Sea, ichthyoplankton were seasonally sampled from 2021 to 2024 around Ulleungdo to assess species composition changes and evaluate spawning and nursery functions. Sampling was conducted at eight stations using bongo and ring nets, and environmental data were recorded with CTD. Fish eggs and larvae were identified morphologically, and COI gene analysis was applied to morphologically ambiguous samples. A total of 37 egg and 48 larval species were identified, with Engraulis japonicus and Maurolicus japonicus dominant in both stages. Cluster and SIMPER analyses revealed interannual variation in eggs and spatial differentiation of larvae after 2023, largely influenced by E. japonicus and M. japonicus. No significant correlation was found with temperature or salinity. However, the increased presence of warm-current larval species in 2023 and 2024, such as Thunnus orientalis, Champsodon snyderi, and Scomber japonicus, coincided with strengthened surface currents, suggesting possible transport from external spawning grounds. The continuous appearance of dominant coastal species supports the role of Ulleungdo as a stable spawning ground, while the irregular occurrence of warm-water species larvae suggests the potential use of the area as a nursery ground under changing oceanographic conditions.