The main culprit appears to be the decline in the salmon population which they eat. What I didn't know about Grizzly bears is that they used to cover much more of the continent and were pushed back to Canada and Alaska when Europeans arrived. The Guardian:
A furious row has erupted in Canada with conservationists desperately lobbying the government to suspend the annual bear-hunting season following reports of a sudden drop in the numbers of wild bears spotted on salmon streams and key coastal areas where they would normally be feeding.
The government has promised to order a count of bears, but not until after this year's autumn trophy hunts have taken place. It has enraged ecology groups which say that a dearth of salmon stocks may be responsible for many bears starving in their dens during hibernation. The female grizzlies have their cubs during winter after gorging themselves in September on the fish fats that sustain them through the following months.
