Good old saw bills. Saving a lot of fish when one of those hits the dirt. On par with a cormorant.
Nasty creatures! Wish you could shoot them and leave lay like a varmint. All the ones I have shot smelled like a week old herring and the dog would not even touch them.
They are also very efficient fish predators. We observed them and kept track at a lake I used to work on and found an average merganser would account for approximately 30 coho fingerlings in a day when the fish were plentiful. When there is a group of ~100 mergansers hanging around in an area you do the math. We also researched the minimal basic metabolic rate on a merg and found they required somewhere around 2-3 oz. minimum of fatty fish to survive, I don't remember the exact figures but it was right in there somewhere.
