Chinese fishmen enter the sea of Japan

Today, I watched Chinese fishmen entered the sea of Japan, and fished on TV. It was illegal fishing. And many Korean and Japanese were hurted by Chinese fishmen. I know all Chinese are not bad, but I can't understand their thought. The reason why Chinese fishmen entered the sea of Japan is pollution of the sea of China. Many industries of China polluted the sea, and fish disappeared from the sea. So Chinese fishman entered the sea of Japan. But I think Japan doesn't do any strict policy in spite of this situation. If the Japanese govement allow the entering more, we will can not stop the entering soon, and more fishmen will enter the sea of Japan. The sea of Japan is valuable resource for us. So I think we should insist our right of sea, and demand Chaina a appropriate measure.