In a popularity contest, the homely little catfish known as the chucky madtom stands no chance against majestic, endangered sport fishes such as the Chinook salmon. Yet the catfish's plight is far more dire: none have been seen in the wild since 2004.

Conservation groups are putting the spotlight on lowly species such as the chucky madtom in a bid to bring attention to the plight of aquatic creatures in the southeastern U.S. Some 70 kinds of snails and mussels, along with two fishes and a crayfish from the region, are believed to have gone extinct. Dozens of other species, including the chucky madtom, are on the brink, devastated by agricultural chemicals, dams and invasive species. Sediment-laden runoff has also taken a toll, particularly on filter feeders. “If water conditions never improve, then they'll just die,” says Tierra Curry, a biologist at the Center for Biological Diversity.

Thanks to the Southeast's stable geology, its wealth of isolated river basins and a lack of Ice Age glaciers, the region is a locus of aquatic biodiversity. The majority of the freshwater mussel, snail and fish species in the U.S. can be found there.

Many animals suffered when hydropower dams started popping up. The construction of seven dams on the Coosa River in Alabama from 1914 to 1967 proved uniquely harmful, wiping out an estimated three dozen species.

More recent threats include increased water withdrawals for human use and mountaintop-removal mining. “It's the conservation crisis that nobody hears about,” says Paul D. Johnson, program supervisor at the Alabama Aquatic Biodiversity Center. “It's certainly unequaled in the United States. There's nothing close to this.”

A few southeastern mussels received endangered status in 2013, but higher-profile species gobble up most of the available funding. In 2012 the U.S. government spent roughly $500 million to protect steelhead trout and Chinook salmon alone, compared with around $13.5 million total on all freshwater snails and mussels. “For them to really survive,” Curry says, “it's going to take cash.”