NIFS said that it clarified the cause of changes in fishing ground formation and environmental changes of largehead hairtail industry in the coast of Jeju Island through Geographic Information System (GIS) analysis. 

The Subtropical Fisheries Research Institute of NIFS confirmed the fact that the water temperature at 20m depth has a lot to do with the formation of fishing grounds for largehead hairtail. The fact was the result from the analysis on the correlation between water temperature changes and fishing ground formation centering on August -the main fishing season for largehead hairtail- based on the data on the NSO* water temperature and hotspots** for fishing vessels focusing on the coastal fisheries in the southern sea over the past decade.

  *NIFS Serial Oceanographic Observation (NSO)  

  **Referring to the radio fishery information communication data (National Federation of Fisheries Cooperatives, NFFC) 

It turned out when the water temperature at 20m depth in August reached 21-23℃, the fishing ground formation was distinctive with the catch increasing (2017), but when the temperature rised to 27-29℃, the fishing ground became degraded or dispersed, resulting in the catch decreasing (2015, 2016, 2023, 2024). 

The largehead hairtail is the No.1 species of fishing yields as a representative specialty of Jeju Island, accounting for the largest share of regional fisheries and local economy. Based on the coastal fishery (coastal composite fishery)* around the southern sea including Jeju Island, however, the catch had dwindled to 3,957 tons in 2024 since 2008 when it hit the highest record 12,212 tons, which represented the operational conditions of fishing households getting worse. 

  *Coastal composite fishery is a fishing sector that catches fishery resources by using a wide range of fishing methods such as longline, octopus pot, shellfish shell fishery, etc. by using unpowered or small power boat (under gross tonnage of 10).  

  **Total catch (National): 63,739 tons in 2006 → 44,507 tons in 2024 (30.2% decrease) / Catch of Coastal composite fishery (Around Jeju): 8,149 tons in 2006 → 3,957 tons in 2024 (51.4% decrease) 

Starting in 2026, to project the changes in the fishing grounds by environmental changes in Jeju seas, NIFS will conduct close monitoring* of the marine organisms and environment from surface to bottom layer within approximately 60km of coast in line with the fishing ground formation period of key fish species.

  *Eggs, young fish, water temperature in each water layer, salinity, dissolved oxygen, etc. will be monitored at 40 stations of eight (8) lines in the sea areas of Jeju. 

The president of NIFS said, “When it is possible to project the changes in marine environment through spatial analysis as well as close monitoring of the environment in Jeju coast, it can reduce the unnecessary travel in looking for the fishing ground, bringing fishery cost cut back. Going forward, NIFS will continue contributing to improving fishery productivity by consistently providing fishermen with useful information based on scientific analysis.”