Sea floor tow-nets damage the ocean bottom and lead to overfishing, so the catch from tow-nets has fallen considerably. In 1971 volume was about 180 kilos per hour, while by 1991 it had fallen to 80 kilos per hour. Pollution has also cut back on local fishing.
因為底拖網對海床造成傷害，以及過度捕捉，拖網漁船的收穫由民國六十年代到八十年代初期，每小時漁獲量的豐度指標由一百八十公斤降到八十公斤，整整少了一半多。