But the authorities can't control them. If you want numbers from Korean side: there were more than 10000 Chinese cutters conducting illegal fishing this year until November. From that number South Korean had caught 'only' around 450 of those. The Chinese fishermen tactics is going into South Korean EEZ in swarms of around 200 cutters at the time. It's coordinated and you just can't catch them all because dealing with a single one takes considerable amount of time and there's not enough South Korean CG manpower to cover it around the vast areas of the seas. Those numbers should show you how big the problem is for Koreans and it's not a great PR action for PRC in South Korea for sure.As for fishing issues with South Korea, there's more than what you post. Evidence that civilian agreements are constructive and producing results.
As for the Japan and whales - I think that everyone has their own view on that matter and there's not much to add to convince anyone that it's bad/good. And I wouldn't call that illegal as well. Calling it 'brute', 'ugly' etc is OK with me but that's another issue and won't threaten the species or people who live from fishing.