Taurusharks are coastal creatures, but at least two of the animals were able to reach inland as far as St. Louis by up the Mississippi River, according to a team of researchers who have examined the fossil record of the shark and reported sightings over the years. .
The research duo – Ryan Shell, paleontologist at the Cincinnati Museum Center and Nicholas Gardner, librarian at WVU Potomac State College with degrees in ecology and evolutionary biology – examined hundreds of reports of sharks in the Mississippi River and compared these historical documents. with archaeological data. and paleontological evidence of bulldog sharks moving through these waterways in the distant past. Their results were published in the journal Marine & Fishery Sciences.
“I think Ryan mentioned something like ‘hey, bull sharks can go up the Mississippi, ”and my first thought was“ bull ****, ”Gardner wrote in an email.
Sharks are known to make forays into freshwater beyond the African, Asian, Australian, and American coasts they inhabit, and the fossil record contains evidence of bulldog sharks in the river, but not in its upper basin. . Some teeth are found inland, but not in natural fossil deposits and in association with teeth from other species, suggesting that they may have been traded inland.
No sightings are documented until the turn of the 20th century, but Shell and Gardner found two confirmed bulldog shark captures in historical records: one in 1937, in Alton, Ill., And another just outside. from St. Louis in 1995. The 1937 shark was an 84-pound and about 5 feet long, according to contemporary reportage by the Alton Evening Telegraph, which said the fish got stuck in a fisherman’s seine net. The 1995 specimen was recovered from the screen of an intake duct of a power plant, according to a 2004 report on the ecology of the waterway; the same report attributed the events of 1937 and 1995 to ephemeral or accidental stray fish.
In addition to these, the observation record is littered with incomplete or erroneous reports, which were often repeated from one source of information to another. These overlapping observations made up the majority of reports reviewed by Shell and Gardner.
“Anyone with access to a computer can build an authoritative website, and if someone doesn’t do the due diligence they need to do, boom, misinformation creeps in,” Gardner said. “We handled the biology side as best we could, now I’m curious as to what drives the hoaxes, misidentification, and more.”
The lack of bulldog shark fossil evidence in freshwater deposits could mean that the adventure of freshwater sharks is a relatively recent development in their behavior. More likely, researchers believe, occasional adventures in freshwater have been a habit of the creature for millions of years, but it just hasn’t been seen in the fossil record. Their third theory is that venturing into Mississippi is so rare for fish that the two specimens caught can be considered anomalous events.
Whatever the ancestral case, Gardner hopes environmental DNA (called eDNA for short) can help scientists understand just how common the behavior is. EDNA allows biologists to take samples of water, soil and even the air to find out what organisms live in that environment, based on the microscopic amounts of genetic information that fall from animals as they move through their habitat.