Okay. I've had an interesting conversation, during which I took notes, with a local marine biologist, particularly regarding the carcasses left on the ice complaint. It turns out the sealers try to take as much as they can that is of use: the pelt, the large flippers which have most of the meat, and as much of the blubber (to be rendered for omega 3 oils) as they can. They are hampered in taking more because of limited space on their boats. Why don't they have bigger boats? Because Canada caved to the antisealers years ago and banned anything but small vessels taking part in the seal hunt. But in fact, there isn't that much meat on a seal body: it's mostly blubber except on the flippers, which are of course taken - up to the point the sealers run out of cargo space.
It's a certainty anything left on the ice gets eaten, by seabirds and by fish and other sea life, so unless you think humans should be the only beneficiaries of their own kills, nothing is wasted.
Lonesome EJ is partially correct regarding pups being killed. Seal pups are called yellowcoats for about three days after birth, then their coat turns white. About eighteen days later, they start to moult and turn silver with a spotted pattern. Sealers can legally kill a pup at eighteen days, but in fact the pelt is not good because of the moult until about thirty-three days, at which point sealers can take them and profit - but they are small pelts compared to an adult seal.
No one alive can ever remember there being as many seals as there presently are. While no one is blaming the seals for the decline of the codfish, it's a fact that the seals do have an impact on the recovery of the codfish. Seals are voracious eaters and they are wasteful killers. If they find a particularly large school of fish, they will bite the liver containing middle out of every fish they can catch and drop the rest. They mostly take big mature breeding age fish, understandable as an adult seal is a big two metre long animal with great big teeth. This I can vouch for directly, as I have a seal skull, misidentified as a bear by most people because of the large, thick canines.