Bull Sharks Keep Being Spotted in the Mississippi River — And Experts Have No Idea Why

In 1937, a five-foot shark was pulled from the Mississippi River near Alton, Illinois, well over a thousand miles from the sea. It was identified, photographed, and filed away. Then it happened again. Bull sharks are the one shark built to leave the ocean behind. They can switch their bodies over to fresh water and swim up rivers for hundreds, sometimes thousands, of miles, and the Gulf of Mexico they set out from is warming and pushing farther inland every year. This is the case for how a shark ends up a thousand miles up the middle of a continent, what the physical evidence actually supports, and where that evidence runs out. Two records on the Mississippi are confirmed. Everything above that number is where it gets complicated. New wildlife documentary every week. Subscribe. Sources: Thomerson et al. (1977); Burr et al. (2004); Shell & Gardner (2021) on the Alton and Rush Island records; Pillans et al. on bull shark osmoregulation; Thorson's Lake Nicaragua tagging work. Primary literature over press coverage throughout. #bullshark #wildlifedocumentary #rivermonsters