Although we can enjoy catching many kinds of fish in the seas of Kochi, we need to be cautious when handling some potentially dangerous fish. Please be especially careful of a fish called "gonzui" which closely resembles a catfish and has poison in the dorsal fin. If stung, you’ll feel intense pain and bleed as well. If you catch one, keep the fish immobilized by placing your foot on the fish’s belly to hold it down (wear thick-soled shoes or boots as the spines penetrate thin shoes) then remove the hook.
A fish called “aigo” also has poison in the dorsal fin and the ventral fin, but it has lower toxicity than gonzui. If you are stung, please wash the sting with water and remove the poison by squeezing the affected area. And then soak the sting in the hottest water you can bear without burning yourself for 30 minutes to 1 hour, so that the poison will lose its potency and the pain will subside. After that you should go to a hospital immediately to receive medical treatment.
Taken from vol.14 PDF