The feeding characteristics of the chub mackerel, Scomber japonicus from Jeju Island waters and the Yellow Sea were compared by analyzing the stomach contents. Large and small purse seines were used to collect 1437 individuals from Jeju Island waters and 1066 individuals from the Yellow Sea. The fork length of S. japonicus ranged from 21.0 to 43.6 cm for individuals from Jeju Island waters and 19.6 to 41.5 cm for those from the Yellow Sea. Based on the index of relative importance and variation in stomach contents according to fish size, S. japonicus was identified as a piscivore and a spatiotemporally opportunistic feeder. The proportion of fish in the diet increased as the body sizes of S. japonicus from both Jeju Island waters and the Yellow Sea increased, whereas the proportion of copepods, amphipods, and euphausiids gradually decreased. Differences in stomach content compositions were observed due to interactions between size and location. Thus, the feeding characteristics of S. japonicus are affected by the abundance and composition of prey in its habitat.

This study aimed to determine how spatial and seasonal variations influence the trophic structure of fish assemblages in the eastern Yellow Sea during 2023. Carbon and nitrogen stable isotope analyses revealed significant but spatially variable differences in δ¹³C and δ¹⁵N values among seasons and sites, without consistent overarching trends. These results suggest that phytoplankton-derived organic matter predominantly supports the regional food web, with isotopic niche shifts reflecting local differences in prey availability and hydrographic conditions. The findings contribute to the development of adaptive, ecosystem-based fishery management strategies amid increasing anthropogenic and climatic pressures.

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.

In this study, the stomach contents of the crocodile toothfish Champsodon snyderi from the offshore waters of the South Sea of Korea were analyzed to understand their feeding characteristics. Bottom-trawlers in the South Sea of Korea were used to collect a total of 228 C. snyderi individuals with lengths ranging from 3.6 cm to 12.3 cm. Based on the index of relative importance and variations in the stomach contents according to fish size, C. snyderi was identified as a spatiotemporal opportunistic feeder that consumes abundant prey resources in the South Sea of Korea. Although no distinct dietary shift was observed with growth, there was a decreasing and increasing trend in the proportion of amphipods and shrimp consumed, respectively, in association with increasing C. snyderi body size in the nearshore waters of the South Sea of Korea. In addition, differences in the stomach content composition were observed in relation to interactions between season and size. Our findings indicate that the feeding characteristics of C. snyderi are affected by the abundance and composition of prey within its habitat.