Changes in catch and revenue structures of coastal and offshore fisheries in the South Sea under climate change: Evidence from mean temperature of the catch (MTC) and mean temperature of ther revenue (MTR)

This study examines changes in the thermal composition of catch and revenue structures in the coastal and offshore fisheries of the South Sea of Korea under ongoing ocean warming. Using annual data on fisheries production and revenue from 1990 to 2025, the study applies the Mean Temperature of the Catch (MTC) and the Mean Temperature of the Revenue (MTR) to assess whether fisheries production and economic value have shifted toward warm-water species. In addition, functional groups and major species are analyzed to identify the principal contributors to these structural changes. The results indicate that both MTC and MTR increased significantly over the study period, with MTC rising by approximately 0.5°C per decade and MTR by approximately 0.3°C per decade. These findings suggest that both catch and revenue structures in the South Sea have gradually shifted toward species with higher thermal affinities. At the functional-group level, fish and cephalopods exhibited significant increasing trends, whereas crustaceans showed no statistically significant long-term changes. Species-level analysis identified warm-water species such as Spanish mackerel, yellowtail, and silver pomfret as major contributors to the observed increase in catch composition. However, changes in catch share and revenue share were not always consistent across species, indicating that shifts in production structure do not necessarily translate into equivalent changes in economic value. Overall, the findings suggest that fisheries responses associated with ocean warming extend beyond biological changes in species composition and are also linked to changes in economic value structures. These results highlight the importance of climate-adaptive fisheries management that considers not only changes in catch composition but also the economic significance of individual species and evolving market conditions.