Commercial fishing on the Mississippi River is for common carp and buffalo. Non-targeted species, such as this catfish, are released. The river contains large numbers of fish species as well as individual fish. NPS/Gordon Dietzman. The fish of the Mississippi River are mostly invisible unless we seek them out with a fishing rod. But these water residents play a vital role in the life of all the river’s neighbors, including people. Fish supply food for otters, eagles, humans, and other fish. Some are critical to the life cycle of mussels. Their presence (or absence) says much about water quality. More than 120 species of fish inhabit the river below St. Anthony Falls, a diversity made possible by the many habitats available in currents, pools, and backwaters.