The waters behind the fish

Northern Alabama · Beaverdam Spring & Creek, Limestone County

A handful of cool, clear, vegetation-rich limestone springs feeding the Tennessee River in northern Alabama — and today, effectively one: the Beaverdam Spring and Creek system. This is the entire world range of the spring pygmy sunfish (E. alabamae), a fish twice believed extinct after the springs it was first found in were impounded or dried, and now federally listed under the Endangered Species Act. Constant-temperature spring water thick with aquatic plants is not just its habitat but its life support.

• Elassoma alabamae

The Carolinas · blackwater ditches & stream margins

The flat, swampy coastal plain of North and South Carolina — tea-dark, acidic water creeping through pine savanna, canal and ditch systems, and the vegetated margins of blackwater streams. Home to the family's two rarest Carolinians, both described only in 1987: the Carolina pygmy sunfish (E. boehlkei) of the Waccamaw and lower Santee drainages, and the bluebarred pygmy sunfish (E. okatie) of a few drainages between the Edisto and the Savannah. Both survive as scattered, small populations in a landscape of ditching and development.

• Elassoma boehlkei
• Elassoma okatie

Florida & south Georgia · the Everglades, the Okefenokee & the Gulf drainages

The peninsula's sloughs, marshes and swamp edges — from the Everglades and the St. Johns north to the vast peat-stained Okefenokee Swamp — plus the shorter rivers of the eastern Gulf coast. Warm, shallow, plant-choked water, often acidic and tannin-dark. Three species divide it: the Everglades pygmy sunfish (E. evergladei), the hobby's staple, across the peninsula and north along the Atlantic plain; the Okefenokee pygmy sunfish (E. okefenokee) in the swamp and the peninsula's interior; and the Gulf Coast pygmy sunfish (E. gilberti), split from it in 2009, in the Gulf-slope drainages from the lower Suwannee west past the Ochlockonee.

• Elassoma evergladei
• Elassoma gilberti
• Elassoma okefenokee

Southern USA · the Mississippi valley, from Illinois to Texas

The great lowland spine of the banded pygmy sunfish (E. zonatum) — the swamps, oxbows, sloughs and backwaters of the Mississippi valley from southern Illinois down to the delta, west into the bayous of Louisiana and east Texas, and east along the Gulf coastal plain through the Mobile basin. Where the other six species are local, zonatum is everywhere quiet water grows thick with plants — the family's type species and its proof that the pygmy sunfish design works at continental scale.

• Elassoma zonatum