Influence of seasonal and spatial seagrass vegetation (Plantae, Zosteraceae) on fish assemblages in southern Geoje Island, Korea

Seagrass beds are vital marine ecosystems that provide habitat and resources for diverse fish communities. This study evaluated the effects of spatial and seasonal seagrass vegetation on fish assemblages inhabiting seagrass ( Zostera marina Linnaeus, 1753) beds around Myeongsa (typically a sandy shore) and Daepo (denser seagrass beds) in the southern coastal region of Geoje Island. Fish samples were collected monthly from September 2009 to November 2010 using a beach seine and push net. A total of 51 fish species (42 species at Myeongsa and 36 species at Daepo) from 31 families were identified across both study sites. The two study sites exhibited distinct seagrass vegetation patterns, with denser seagrass at Daepo and relatively sparse seagrass at Myeongsa. At Myeongsa, Takifugu niphobles (Jordan et Snyder, 1901), Aulichthys japonicus Brevoort, 1862, and Syngnathus schlegeli Kaup, 1856 were the most dominant species (in terms of frequency of occurrence). In contrast, Daepo was dominated by Rudarius ercodes Jordan et Fowler, 1902, Hexagrammos agrammus (Temminck et Schlegel, 1843), and Paracentropogon rubripinnis (Temminck et Schlegel, 1843), highlighting habitat-specific differences between fish assemblages and common fish species. Fish species richness, abundance, and diversity varied substantially depending on habitat type and season. Myeongsa, which was dominated by Takifugu niphobles , had the highest fish abundance, whereas Daepo exhibited a more balanced and diverse species composition. Non-metric multidimensional scaling analysis further demonstrated that habitat and season significantly influenced fish assemblage structure, with seasonal variations in abundance correlating with changes in seagrass biomass and temperature. Our findings provide baseline data for the conservation and management of seagrass-associated fish communities in Korea and contribute to broader efforts to sustain biodiversity within coastal habitats.