Thank you for your reply! That's all very interesting. I can believe fishermen would feed sharks like that, it seems so irresponsible. I remember reading that bear attacks at campsites were greatly reduced by making sure all food was locked up so the bears wouldn't come looking for it and then associate people with deliciousness. It seem like the same sort of principal might apply here. I'm sure there are many factor at play here, and I thought your idea about overfishing open waters playing a role was particularly intriguing.