As far as the "Belching", I have not read any research on the topic, but I will make an educated guess. As I mentioned to Ty once, fish can fill their swim bladders in two ways. They either have specialized cells in the lining of the swim bladder that takes oxygen from the blood stream or they have an opening that connects the GI tract to the swim bladder and fill it by "gulping" air. Musky and Pike have the latter type. It is possible that when we take fish out of the water, they unintentionally overfill their swim bladder. This may be disorienting to the fish. I have never had to "burp" a musky, but have seen it be useful on other species I have sampled.