Species Focus Area
Freshwater habitats hold a remarkable share of biodiversity in a very small share of the earth's water, and they are easily disrupted.
Springs, creeks, and small rivers concentrate endemic species found nowhere else. A single spring going dry can end a species outright.
Common threats
How people can help
These ten are not a scientific ranking. They were selected for conservation urgency, teaching value, and regional relevance, and each one has a complete, sourced profile.
Vulnerable (IUCN); ESA listing proposed for the eastern subspecies
Cryptobranchus alleganiensis alleganiensis
North America's largest salamander, breathing through its skin in fast, clean streams and disappearing as those streams fill with silt.
Vulnerable (IUCN) / Endangered (ESA)
Etheostoma fonticola
A thumb-sized fish living only in the Comal and San Marcos spring systems of central Texas, dependent on constant spring flow.
Vulnerable (IUCN) / Endangered (ESA)
Eurycea sosorum
A gilled salamander that lives only in the spring outlets at Barton Springs in Austin, Texas, and nowhere else on earth.
Critically Endangered (IUCN) / Endangered (ESA)
Zizania texana
An aquatic grass that grows in the wild in exactly one place on earth: the upper two miles of the San Marcos River in Texas.
Endangered (ESA) / Endangered (Texas)
Lampsilis bracteata
A freshwater mussel found only in central Texas rivers, filtering water for decades in one spot and dying when the river stops flowing.
Critically Endangered (IUCN) / Endangered (ESA)
Quadrula fragosa
A freshwater mussel once found across a dozen states, now surviving in a handful of river reaches, principally the St. Croix River on the Minnesota-Wisconsin border.
Endangered (ESA)
Heterelmis comalensis
A beetle the size of a grain of rice that lives only where Edwards Aquifer water emerges at two Texas spring systems.
Critically Endangered (IUCN) / Endangered (ESA)
Hybognathus amarus
Once the most abundant fish in the Rio Grande, now restricted to a fraction of the river and dependent on hatchery releases and managed flows.
Critically Endangered (IUCN) / Endangered (ESA)
Scaphirhynchus albus
A Missouri and Mississippi River sturgeon that has largely stopped reproducing in the wild because the rivers no longer flow the way its eggs require.
Critically Endangered (IUCN) / Endangered (ESA)
Cyprinodon diabolis
The rarest fish in the world, living entirely in one water-filled limestone cavern in the Nevada desert.