Why Do Muskies Gulp Air?
by Gord Pyzer
I was texting the other day with friend, Charlene Snow, the owner of Eagle Lake Island Lodge located between Vermilion Bay and Dryden, Ontario. Charlene is a muskie-fishing fanatic like me and reported that several of her guests this season have spotted muskies swimming just below the surface with their heads exposed and their mouths wide open. Why in the world would a solitary apex predator behave this way, she wondered?
I’ve had muskies show up unannounced when I’ve been fishing and suspend just below the surface, all the while watching me intently, but I’ve never witnessed one with its head and mouth above the water in a Loch Ness pose. So I contacted two of the brightest minds in the muskie science field to get their thoughts on what the fish may be doing.
Dr. Sean Landsman authored the brilliant Project Noble Beast when he tracked muskies on the Ottawa River. Sean is currently an instructor at the Institute of Environmental and Interdisciplinary Science, at Carleton University in Ottawa and president of the American Fisheries Society’s Science Communication Section. He suspects the behaviour is related to buoyancy regulation.
“Muskies are physostomous, so they have a little duct that connects their swim bladder to their esophagus and thus, the outside world,” he says. “This means they can gulp air to try and increase buoyancy or burp air to lose buoyancy. But why they need to do this is unclear. Are they having some sort of physiological issue that is preventing them from moving gas into their swim bladder? Did they just eat a large meal and need to compensate for the added weight by increasing buoyancy? To the latter, there’s some research with farmed salmon smolts that demonstrate smolts gulping air after ingesting lots of food.”
Winter lake trout and whitefish anglers are familiar with how physostomous species will burp air out of their swim bladders to compensate for the pressure change when they’re hooked and brought to the surface. Walleye, yellow perch and bass anglers, on the other hand, are aware of what can happen to non-physostomous or physoclistous fish. Being unable to regulate their air bladders and compensate for a change in pressure, their bladders swell up like balloons when they’re brought up to the surface from deep water, making safe release problematic.