From the Arctic National Wildlife Refuge to the alpine streams of the Rocky Mountains to the Little Tennessee River, freshwater is an important habitat for wildlife, and often a hotspot of biodiversity.

Fish like Dolly Varden, Arctic grayling, delta smelt, longfin smelt, bull trout, greenback cutthroat trout, rio grande cutthroat trout, blackside dace, Carolina madtom, spotfin chub, wounded darter, cumberland darter, sicklefin redhorse, Yaqui catfish and many other species all rely on these freshwater habitats.

Unfortunately, humans have many impacts:  draining, dredging, damming and channeling wetlands, rivers and streams; converting wetlands into cropland, pasture and subdivisions; mining the underlying resources; filling streams and weltands for roads or flooding them for reservoirs and lakes; and using them for dumping grounds for waste and sewage.

Climate change is increasing stream and river temperatures throughout the country, which is problematic for many native fish like salmon and trout, which can die if temperatures are too high. 

Defenders' Impact

Defenders is fighting for clean water protections throughout the country, and especially in the Southeast, which is a hotspot of freshwater biodiversity.

We are bringing enforcement lawsuits against polluters for illegally discharging pollutants from coal ash landfills and other point-source pollution.

In the Northwest, we are advocating ways to reduce pollution with our Orcas Love Raingardens program and remove outdated dams from rivers in the region to restore salmon.

We are relocating “nuisance” beavers in the Rockies and Plains to promote healthy wetlands and waterways and provide habitat for freshwater fishes and other aquatic species.

We are also working across the country to protect aquatic connectivity for freshwater fish and we participate in reintroduction projects for species that have been displaced, like the Rio Grande cutthroat trout and greenback cutthroat trout. 


Habitat loss and fragmentation, sedimentation, climate change, invasive species and pollution are all threatening freshwater fish across the country.

What You Can Do

Limit pesticide use. Obey all signs and instructions about washing boats, gear and boots to avoid transporting invasive species. 

Agnatha, Chondrichthyes, Osteichthyes
Freshwater fish range in size from the least killifish, which only about an inch long, to sturgeons, which can be 15-30 feet long and weigh nearly one ton.
a few weeks or months to years or decades (sturgeons can live for over 50 years)

Freshwater fish are found in the widest rivers and the deepest lakes to some of the smallest headwater streams all across the country.


Many populations are small and fragmented, making population estimates extremely difficult.


Some fish, like salmon, smelt and sturgeon, are anadromous and migrate upstream from the ocean to spawn. Some fish give birth to live young, but others lay eggs.


Most freshwater fish eat a combination of insects and other invertebrates, some plants or smaller fish.


Students, parents and faculty from FernLeaf Community Charter School remove invasive plants and plant new growth along the bank of Cane Creek in Fletcher, N.C.
Fletcher, N.C.

Shade Your Stream Program Plants New Life Along North Carolina Creek

The banks of Cane Creek came alive Friday with hard work — much of it by small, determined hands. Students of the FernLeaf Community School

Freshwater Fishes Blog Posts

Wildlife and Wild Places

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