A Fishing Ground Changed by the Warmth of the Kuroshio Current: The Story of Mackerel in Kinan, Wakayama Prefecture (1993-2005)

A Fishing Ground Changed by the Warmth of the Kuroshio Current: The Story of Mackerel in Kinan, Wakayama Prefecture (1993-2005)

--- (1993-2005)

A slight rise in sea water temperature along the coast of the Kinan region of Wakayama Prefecture has quietly changed the landscape of the fishing industry over the years. In the past, the only fish that lined the fishing harbors of this region were the fatty chub mackerel. In recent years, however, the number of mackerel has been declining, and sesame mackerel have begun to take their place in the nets. According to a survey conducted by the Wakayama Prefectural Fisheries Experiment Station, the water temperature at a depth of 100 m was 15 degrees Celsius until 1993, but it rose to 16 degrees Celsius in 1995 and to 17 degrees Celsius in 2002 and later. A change of only a few degrees has changed the sea for mackerel.

As a result, in 2003, sesame mackerel surpassed chub mackerel in terms of catch, and by 2005 accounted for about 80% of the mackerel caught in Wakayama Prefecture. However, this shift has not been a happy one for the fishermen. Goma saba has a low market reputation, and its price is only half that of masaba. The fruits of a fishery that they once took pride in are now weighed down by the loss of revenue.

This story shows how the distant topic of global warming casts a shadow over the lives of those who live with the sea. A change in sea temperature of just a few degrees can upset the balance of the ecosystem and even change the state of the economy. The sea in Wakayama is now quietly telling us: "As the sea changes, so does our way of life. Science, experience, and patience are being called into question as to how we can continue to live with the ever-changing sea.

The catch of sesame mackerel has been on the rise since the 1970s in the western Sea of Japan and the East China Sea, reaching about 50,000 tons per year in 2011. In contrast, the catch of chub mackerel plummeted in the early 1990s and has remained stagnant since then. Rising sea temperatures and changes in migration routes are believed to have spurred this reversal phenomenon.

---In contrast, the catch of chub mackerel has been stagnant since the early 1990s.

Related information
- Fisheries Agency, Fisheries Research and Education Agency: Mackerel Stock Assessment Report (2023)
- The same organization: Report on Mackerel Resources (2024)
- Wakayama Prefectural Fisheries Experiment Station: Kinan Region Fisheries Research Report (Wakayama Prefecture official website)