Why do the bears get bigger here? The reasons aren't fully understood, but they almost certainly have something to do with genetics, a stable population of about 8,000 bears, ample food supply and relatively low hunting pressure. I can vouch for the size of the bears here from personal experience. The two largest black bears I've ever seen in the wild were both encountered at different times on different sections of the island, while hunting primarily for moose and/or woodland caribou. I managed to shoot the smaller of the two. It weighed 450 pounds field dressed, squared over six feet (Newfoundland bears tend to be short and blocky, so "squared" is a very accurate description of the hide), and had a skull that green-scored close to 20 inches. The one that got away was considerably larger.
A good first contact, when planning a hunt in Newfoundland, is Dan Chaisson in the Provincial Tourism Office. He can give you a list of outfitters and make some general recommendations based on your priorities. Dan is a hunter himself and can help point you in the right direction, though he can't direct you to any one outfitter.
Wayne Barney, the bear biologist for the island, is also well worth talking to, although like all biologists, he's reluctant to deal in absolutes. According to Barney there are bears everywhere on the island with the possible exception of the Avalon Penninsula, which doesn't have any hunting outfitters anyway. The populations are highest in the forest lands of........(continued)