Bull sharks typically live in warm ocean saltwater, but they are able to survive a long time in freshwater, and the two discoveries in Illinois were both on the Mississippi River. The sharks journeyed over 1,100 miles up the Mississippi River from New Orleans.
According to the Illinois Department of Conservation, two commercial fisherman from Alton, Herbert Cope and Dudge Collins, caught a bull shark in 1937. The fishermen suspected a fish was messing with their wood and mesh traps late in the summer, and they built a strong wire trap and baited it with chicken guts. The next day, they caught a five foot, 84-pound shark, which they displayed in the neighborhood Calhoun Fish Market. The shark attracted crowds for days, and biologists were able to conclude from photographs that it was indeed a bull shark. The second shark sighting involved a bull shark being caught in 1995 at a location south of St. Louis, near the Rush Island power plant.
Rare appearances of bull sharks in river systems and other freshwater ecosystems have been reported from five continents. Excluding the 1937 and 1995 discoveries, no other known bull shark sightings have been confirmed in the Mississippi River basin north of Louisiana. Experts have debated the random nature of these occurrences and also wondered how many of these large bodied, aquatic apex predators have entered the upper Mississippi River without detection to this day.