The cod fisheries were able to be harvested beyond their ability to recover because . the Cod fisheries were tightly regulated, with catch limits imposed on all fishing vessels the Canadian and U. S. governments excluded all foreign fisheries in a zone extending 200 miles around the habitat Cod were caught by large commercial trawlers with purse nets enabling a very high level of removal when the number of cod declined, humans switched to fishing for other species the cod that were harvested were of post-reproductive age, thus having little affect on the overall population growth