Bull Sharks in the Great Lakes, or Just Plain Bull?


According to one of the online sites I monitor, there was apparently a shark sighting reported in Lake Michigan near Frankfort, Mich., and that’s not the first one I’ve ever heard about in this water.

So are there sharks in the Great Lakes?

My guess is no. The chance of there being a shark in the Great Lakes is worse than the chance I’ll win the Lottery or that a meteorite will fall from the sky and sink my boat next time I go fishing. However, while channel surfing during the Discovery Channel’s Shark Week in midsummer, one title from a program caught my eye—”Monsterquest: Jaws in Illinois.” It told a tale of oceanic sharks swimming up the Mississippi River as far as Illinois.

Southern Illinois is still a long way from Lake Michigan, but they are connected. The tip in downstate Illinois is also a long way from the Gulf of Mexico too. So I suppose if a shark with a case of northerly wanderlust could make it to the Illinois River north of St. Louis, it could make it the rest of the way.

What kind of shark could it be? A bull shark? This species isn’t as well known as the famous great white in Jaws, but it has a unique trick—its kidneys can recycle salt vital to the animal’s cells. Normally, a freshwater dip would dilute the salt in a shark’s body, causing its cells to rupture and kill it. Recycling the salt its body already contains allows bull sharks to adapt to a freshwater environment. Bull sharks are one of a very few of the 375 species of sharks with this physiological-altering ability, and they do it better than any other.

These have been found in freshwater around the world, including in water thousands of miles up South America’s Amazon, in lakes in Central America, and, evidently, as far up the Mississippi as Illinois according to National Geographic.

“Bull sharks couldn’t really deal with the winter temperatures in the Great Lakes, or the scarcity of food, but it’s possible that if one swam in, it could live for a while,” said Amber Peters, an assistant professor specializing in marine ecology in Michigan State’s Department of Fisheries and Wildlife.”

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No shark reports have been officially, “scientifically” documented in Lake Michigan. There have been “fin” sightings as was the case in Frankfort. There have been reports of dead sharks apparently washed up on the beaches in Lake Huron, Erie and Ontario, but there’s no way to tell whether they came on their own or were planted there as pranks. I couldn’t find any reports for Lake Superior.

Of course, the lack of saltwater and appropriate food, and the colder temperatures in the water are hardly the only obstacles keeping a shark from reaching the Upper Great Lakes. Actually, the prevalence of Asian carp in the Mississippi and other Midwestern waterways could provide a never- before abundant food source for the bull sharks. However, even one venturing up the Mississippi River Basin would have to get through the electric barrier at Chicago that’s designed to keep invasive species out of Lake Michigan. One venturing from the Atlantic Coast into the St. Lawrence River would have to negotiate that seaway’s lock system and then make it through the locks in the Welland Canal or swim up and over Niagara Falls to access the Upper Great Lakes.

Most likely, shark fin “sightings” on the Great Lakes are either an apparition brought on by the sun, waves, fantasies or alcohol—or they could just be lake sturgeon. A big sturgeon does have a healthy, shark-like dorsal fin and tail, and they have been known to swim near the surface.

But maybe this is just the newest “invasive species” to show up. I caught a bull shark once in the Florida Keys and it was one of the toughest customers that ever stretched my line. Of course, I don’t often have the chance to hook-up with fish around 8 feet long and that weigh 200 pounds or so. If they want to populate the lakes, bring ‘em on. I’m ready for a rematch.

Bull sharks have attacked humans though. I don’t know if they’ve actually eaten anyone, but reports of arm and leg amputations due to their bites aren’t hard to find.

All in all, I’ll continue worrying about errant meteorites about as much as I will with bull sharks in the big lake. But then, just a couple of them patrolling Lake Michigan’s shoreline would certainly add a measure of adventure, don’t you think?