Natural History

Imagine seeing one of these swimming around in a Midwestern lake.

The question of how far up a river a bull shark can live has often brought debate. Although one was found over 2,000 miles  up the Amazon in Peru, it is thought that bull sharks cannot survive very far up North American rivers, and they certainly could never be found in the cold rivers and lakes of the Northern tier of states. Or could they?

It is well-known that bull sharks can tolerate fresh water. In fact, their tolerance for fresh water has resulted in taxonomists naming them after the rivers and lakes they frequent. In Southern Africa, the species is called the Zambezi shark.In Australia, it is known as the Fitzroy creek whaler, and in Lake Nicaragua it is called Nicaragua Shark. In all of these cases, it was thought to be an endemic river species. Now, we know them all to be bull sharks.

Several species of true river sharks can be found in Asia and tropical Australia. These are in the genus Glyphis. The most famous is the Ganges shark, which is quite endangered. It is often considered quite dangerous and is blamed for attacks on Hindu pilgrims. However, it is very likely that this species is taking the blame for bull shark attacks.

Now, in North America, the only river shark we have is the bull shark. It is the species that is most likely responsible for the shark attacks that happened at Matawan Creek, New Jersey, in 1916. It is likely that a great white was preying on people on the Jersey Shore at the same time, for a great white was caught in in Raritan Bay with human remains in its stomach. It is also possible that the shark had been feeding on corpses lost at sea. After all, the First World War was raging at the time, and great whites have been known to swim vast distances across the ocean. However, there were shark attacks on the coast during that time period. These could be attributed to a great white, which are known to hunt in the surf.

Because they happened at roughly the same time as the shore attacks, the attacks in Matawan Creek were blamed on the same shark. However, great whites cannot swim up freshwater estuaries. They cannot regulate their salt content in that sort of water, and they die. Bull sharks, however, can swim up fresh water rivers rather easily. Most experts believe the Matawan shark was a bull shark.

Officially, bull sharks have made it up the Mississippi as far as Illinois. In the town of Alton, Illinois, which is above St. Louis, two commercial fisherman caught a bull shark in the river. This shark had been raiding their fish traps, and they decided to catch the culprit once and for all. They set a big trap, one that would catch the biggest muskellunge or pike.  They were certainly shocked to find that it was a shark raiding their traps.

Now, there is another interesting story that should be added. Although now official record of it exists, a man was supposedly attacked by a shark in Lake Michigan in 1955. This attack supposedly happened at one of the beaches near Chicago. The shark may have traveled through the Illinois River and then took a trip up the Michigan and Illinois Canal. However, the canal was disused and parts of it had already started falling in. It could have made it up the St. Lawrence Seaway and into the Great Lakes system. How it made it through the locks and dams on the St. Lawrence is a very good question. Further, bull sharks have been found only as far north as Massachusetts. None have been reported in the Gulf of St. Lawrence, where they could enter the river and seaway.

This story may be an urban legend.

However, I have found a more recent story that might add some credence to the Lake Michigan shark legend.

In the winter of 2006, sharks were documented in Minnesota and Wisconsin. Yes, you read that correctly.  Not only are both of those state quite far from the ocean, they are also known for their less than temperate winters. The Mississippi’s source is in Minnesota, and Minnesota and Wisconsin are the first two states it passes on its way to the Gulf of Mexico.

Our story begins in Minnehaha creek, not far from the city of Minneapolis. There, a ten year-old girl named Laura Zimmerly found three shark’s teeth. She brought the teeth to Minnesota DNR biologist Dan Marais. Marais’s first reaction was that these were fossilized shark teeth. Fossilized shark teeth were not uknown in the Upper Mississippi region. However, two of the teeth were rather obviously not fossils. They looked like they had just fallen from a shark’s jaws.

The two teeth were sent to the fisheries department for further analysis.

The teeth were those of a juvenile bull shark.

Now, that was in the autumn of 2005. The two teeth were interesting, but because they were of a juvenile, no one really got excited about them. The case of the Minnesota shark teeth was classified, and no one made a big deal about it.

Then in Februrary of 2006, a pickup truck went through ice in Lake Pepin. Lake Pepin is a widening of the Mississippi between Wisconsin and Minnesota. It is also a lake with its own lake monster, known as “Pepie.” (Now that first photo looks hoaxed). However, when that truck went through the ice, a real live monster made sought refuge within the vehicle.

Salvage divers reported a shark that had moved into the vehicle. Now, it could have been a sturgeon, so Wisconsin’s DNR sent biologists to go check it out. In about 18 feet of water, the biologists discovered a five foot-long bullshark resting within the truck. It was comatose and near death. The cold water and the lack of trace elements in the Mississippi River water were taking their toll upon the creature. It had sought out the truck as a place of safety.

Now, the story of the Minnehaha shark teeth suddenly became of importance to the authorities. Minnesota’s DNR sent a team of researchers who used electric current to stun the fish of creek. Among the fish that were stuned were two very small bull sharks. These baby sharks were christened “Frankie” and “Lenny” (from the movie Shark Tale). They were sent to the Minnesota Zoo, where they were reacclimatized to salt water.

Now, it is thought that the five-foot in Lake Pepin and these two juveniles in Minnehaha Creek swam up the Mississippi becaus of Hurricanes Katrina and Rita. The storms washed large amounts of pollution into the Gulf of Mexico, which killed off lots of prey species for the bull sharks. Bull sharks tend to live very close to shore, and they also tend to live near river mouths. With the temporary extirpation of typical prey species, these sharks swam up the Mississippi. Because the locks and dams were being opened to prevent flooding, the sharks continued to swim up the river until they were very far from their typical range in the Mississippi.

However, the teeth that Laura Zimmerly found were tested for their age. The DNR tested the tannin stains on the teeth. Tannin is the residue from leaves that drop into the river. The longer the teeth were in the creek, the more stain they would have. The teeth were found to have been in the creek for seven years. That means that bull sharks have been occasionally frequenting the Upper Mississippi for a really long time. It also means that bull sharks are coming up these rivers with far more frequency than had previously been assumed.

Minnesota authorities banned swimming and diving in Minnhaha Creek below the famous Minnehaha Falls that summer. No one wanted to be the first Minnesota shark attack victim.

Now, closing down the creek below the falls to swimmers sounds rational, but I have to offer this caveat. The bull sharks of Lake Nicaragua are only able to enter the lake the lake through the San Juan River, which has fast flowing rapids and falls. The sharks were once thought to be trapped in the lake. However, the sharks never seemed to be reproducing in the lake. It was later found that the sharks were jumping the rapids  on their way into the lake. I doubt that the bull sharks could jump Minnehaha Falls, but it was also doubted that they could ever make it that far up the Mississippi.

Now, I have not read of any sharks making it up into my neck of the woods. The rivers in my area all drain into the Ohio, which drains into the Mississippi. Bull sharks have been found in the Ohio, but they have not been found outside the Lower Ohio drainage.  As far as I know, no sharks have been found in the Upper Ohio or its tributaries. But if a shark could make it to Minnesota, it certainly could make it to West Virginia, and it might be able to survive a little longer in the winter. In fact, if the winter was a very mild, it might be able to survive.

However, if there is going to be a shark in West Virginia, it is more likely to be found in the Potomac drainage system. The Potomac is much closer to a body of salt water (Chesapeake Bay), and the sharks have been seen in the Potomac as far up as Washington, D.C.

Now, things wouldn’t be so bad if bull sharks weren’t known for their very high levels of aggression. In fact, most shark attacks in the world are probably from bull sharks. Bull sharks have very high levels of testosterone. In fact, they have higher levels than bull elephants in musth. These high levels might make them more aggressive than other species. Further, they are typically found only in shallow water near river mouths. Those are the same sorts of areas where people swim and fish.

So bull sharks can turn up just about anywhere. However, I doubt that Minnesotans will be ice-fishing for them any time soon.

And they definitely won’t . Please read this post before leaving ANY comments that call me an idiot. I’m a fibber in this case, not an idiot. Remember, I’ve been reading Montauk Monster conspiracy theories for a week, so I thought I’d try my own hand at some “grade A bull-plop,” as “Mr. X” (Homer Simpson) once said.