The US generally has sustainable fishing and farmed-fishing laws and monitor catches and stocks. I don't know if there is a law that tracks nets per boat, but maybe there should be. Regardless, if you keep track of where your fish comes from (US wild caught and US farm-raised [farmed excluding salmon because they eat more protein than they produce]), then you (as far as I know) are not contributing to these problems. Buying fish exported from countries lacking oversight is the real problem.