Bowfin
(Amia calva)

The bowfin (Amia calva) is a bony fish related to gars in the infraclass Holostei. Common names include mudfish, mud pike, dogfish, griddle, grinnel, swamp trout, and choupique.

It is regarded as taxonomic relicts, being the sole surviving species of the order Amiiformes, which dates from the Jurassic to the Eocene, persisting to the present.

Although highly evolved, the bowfin is often referred to as a primitive fish because they have retained some morphological characteristics of their early ancestors.

Bowfins are demersal freshwater piscivores native to North America, and commonly found throughout much of the eastern United States, and in southern Ontario and Quebec. Fossil deposits indicate Amiiformes were once widespread in both freshwater and marine environments across North and South America, Europe, Asia, and Africa.

Now, their range is limited to much of the eastern United States and adjacent southern Canada, including the drainage basins of the Mississippi River, Great Lakes, and various rivers exiting in the Eastern Seaboard or Gulf of Mexico. Their preferred habitat includes vegetated sloughs, lowland rivers and lakes, swamps, and backwater areas; they are also occasionally found in brackish water. They are stalking, ambush predators known to move into the shallows at night to prey on fish and aquatic invertebrates such as crawfish, mollusks, and aquatic insects.

Like gars, bowfin are bimodal breathers – they have the capacity to breathe both water and air. Their gills exchange gases in the water allowing them to breathe, but they also have a gas bladder that serves to maintain buoyancy, and also allows them to breathe air by means of a small pneumatic duct connected from the foregut to the gas bladder. They can break the surface to gulp air, which allows them to survive conditions of aquatic hypoxia that would be lethal to most other species.