What is a Fish?
Fishes are vertebrates belonging to any of three taxonomic groups: superclass Agnatha, class Chondrichthyes, and superclass Osteicthyes. Fishes with bony skeletons and fins are members of superclass Osteicthyes, while fishes with skeletons formed of cartilage are members of class Chondrichthyes. Fishes such as lampreys that lack jaws are members of superclass Agnatha . Fishes include familiar animals such as Catfishes (order Siluriformes) and Salmons (order Salmoniformes). Thought of as "cold-blooded," fishes are ectotherms, meaning they are unable to regulate their own body temperature independently of the temperature of their surroundings. Fish characteristics include anatomy adapted for aquatic life including gills, streamlined body shape, fins, and skin covered by scales. Reproduction strategy among fishes can vary, ranging from bearing live young to egg laying.

Southeastern Species of Greatest Conservation Need Learn more about regional fish species of greatest conservation need by browsing our species information Web application.

In Alabama, Kentucky, Mississippi, and Tennessee, fishes are represented by numerous taxonomic orders seen below:

Superclass Agnatha

Lampreys (order Petromyzontiformes)

Class Chondricthyes

Ground sharks (order Carcharhiniformes)

Superclass Osteicthyes

	Bonytoungues (order Osteoglossiformes)
	Bowfin (order Amiiformes)
	Catfishes (order Siluriformes)
	Cods (order Gadiformes)
	Cyprinodonts, killifishes (order Cyprinodontiformes)
	Cyprins, Minnows, Suckers (order Cypriniformes)
	Eels (order Anguilliformes)
	Flatfishes, Flounders (order Pleuronectiformes)
	Gars (order Semionotiformes)
	Herrings (order Clupeiformes)
	Leporins, Piranhas (order Characiformes)
	Mudminnows, Pikes (order Esociformes)
	Mullets (order Mugiliformes)
	Needlefishes (order Beloniformes)
	Paddlefishes, Spoonfishes, Sturgeons (order Acipenseriformes)
	Perch-like fishes (order Perciformes)
	Pipefishes, Sticklebacks (order Gasterosteiformes)
	Salmons (order Salmoniformes)
	Silversides (order Atheriniformes)
	Smelts (order Osmeriformes)
	Tarpons (order Elopiformes)
	Trout-perches (order Percopsiformes)

Ecological Importance of Fishes
Fishes play several important roles in aquatic ecosystems. As consumers, they help regulate populations of aquatic organisms they prey upon, including aquatic invertebrates, plants and algae, and other fishes and smaller animals. Scavenging fishes contribute to water quality by removing decaying organic matter from the ecosystem as they feed. As prey items, fish, fish fry (juvenile fish), and fish eggs are consumed by a variety of predators, both terrestrial and aquatic.

Fishes of the Southeastern United States
The southeastern United States is home to an unparalleled diversity of temperate freshwater fishes. Within southeastern U.S. states including Arkansas, Louisiana, Mississippi, Alabama, Florida, Georgia, North and South Carolina, Virginia, and Kentucky, there are 530 freshwater fish taxa, representing 66 percent of all freshwater species in North America (Hamilton, 2003). The Southeast has approximately 485 known species of native freshwater fishes, representing 27 taxonomic families (Walsh, Burkhead, and Williams, 1995). Of those 27 families, five have the greatest diversity: perches, minnows, madtoms and bullhead catfishes, suckers, sunfishes and basses. Freshwater species diversity can be attributed to the abundant major river systems in the region, including the Ohio, Tennessee, Cumberland, and Mobile Rivers and tributaries.

In Alabama, Mississippi, Kentucky, and Tennessee, freshwater and marine fish species number as follows: in Alabama, there are 340 species including 12 exotic species; in Kentucky, there are 263 species including 14 exotic species; in Mississippi, there are 253 species including 13 exotic species; in Tennessee, there are 307 species including 10 exotic species [source: NatureServe Explorer Database].

For more about marine and freshwater fishes of Alabama, Mississippi, Kentucky, and Tennessee, refer to the NBII catalog query for fishes on our "Fishes Web Resources" page listed on the navigation menu at left.