7 local animals making a comeback thanks to clean water

Reduced pollution in the Potomac is welcome news to local wildlife

ATlantic Horseshoe crabs ( Limulus polyphemus)  are one of several species making comebacks thanks to cleaner water in the potomac river.

ATlantic Horseshoe crabs (Limulus polyphemus) are one of several species making comebacks thanks to cleaner water in the potomac river.


If you haven't heard the news, the Potomac River is the healthiest it has been in decades. And as happy as we are about that, we can't possibly be as happy as the fish, birds, and four-legged friends we share this river with.

Thanks to improving water quality and conservation efforts, we're seeing a return of some spectacular animals that have long been in decline.

Here are some of the animals that are heading back into our neck of the woods — or should we say bend in the river. 


Bald Eagles

Photo courtesy of Richard Orr.

Photo courtesy of Richard Orr.

In the 1970s, bald eagles, and other fish-eating birds like osprey and blue heron, had all but died out in our region. When recovery efforts began in 1977, local states set a goal of 300 nesting pairs.

Today, scientists estimate there are over 3000 nesting pairs of bald eagles in the Chesapeake Bay region. There are even several breeding pairs in Washington, D.C. - something conservationists couldn’t have imagined 40 years ago.

The bald eagle's comeback is thanks in large part to the banning of pesticides like DDT, which made eagles' eggs too thin to survive. But improving local water quality is also playing a role as eagles rely on fish for food. Cleaner water and improving fisheries means eagles are once again calling the banks of the Potomac home! 

🌟 Species Fun Fact: The stunning comeback of bald eagles’ doesn’t only mean can you regularly spot them along the river, it has also provided a vital data set for scientists working on the recovery of other endangered species.


American Shad



The Potomac River is a regional success story for the American shad, a fish that once supported the highest-dollar commercial fishery in the region but has faced massive population declines. 

While the exact causes of shad’s return to the river aren’t entirely clear, a cleaner river, harvest moratoriums, stocking programs, dam removals, and the restoration of tidal grasses seem to have played a part, according to the Interstate Commission on the Potomac River Basin.

So just how well are the fish doing? At last check, the Potomac's shad population was exceeding restoration goals at 130 percent of the target! Shad’s comeback in the Potomac is uniquely successful as the Susquehanna, James, and other Bay rivers have seen minimal gains.

🌟 Species Fun Fact: Shad are an anadromous species, meaning they live in the ocean but return to the freshwater rivers and streams in which they were born to spawn. That means a shad could swim over a thousand miles just to get back to its home in the Potomac!



seahorse potomac river

Seahorses? Here? That's right. A species called lined seahorses (Hippocampus erectus) can be found throughout the Chesapeake Bay and some of its tributaries in the summertime. They thrive in salty water, so if you're looking to spot one, head south toward the lower portions of the Bay. 

Seahorses are a sensitive indicator of water quality because seahorses rely on underwater grasses for food and shelter. Underwater plants can only grow in clean water with the right amount of oxygen and sunlight. Increasing seahorse populations mean that the Bay’s water quality is improving and that salinity levels (how much salt is in the water) are in a healthy range. However, we need to keep fighting for this precious creature as increased rainfall and runoff threaten the Bay’s delicate balance!

🌟 Species Fun Fact: Seahorses aren’t strong swimmers, so they rely on their color-changing camouflage abilities to evade predators. This also makes them tough fro scientists to find!


Blue Crabs

blue crab chesapeake bay potomac river

In 2019, local blue crabs are at their most plentiful in 7 years. Blue crabs are a notoriously fickle population, but harvest restrictions and conservation efforts seem to be paying off.

Blue crabs need thick underwater grasses to survive and reproduce. Dead zones and algal blooms have drastically reduced the amount of underwater grass in the Bay. Yet, despite record rainfall and warmer waters in the past year, Bay grasses have been resilient. This is in part because of the positive feedback loop they create: clean water grows healthy grasses, which in turn clean the water, creating a habitat for more grasses to grow and wildlife to thrive.

🌟 Species Fun Fact: Blue crabs don’t just feed humans, they are vital to the diets of waterbirds and fish like striped bass, red rum, catfish, and sharks. Juvenile blue crabs are even eaten by other blue crabs, which can make raising them via aquaculture difficult.



Beaver potomac river

Of all the animals on this list, it was the beaver that's been closest to extinction. But the last few decades have been kind to nature's engineers, and scientists are now learning just how beneficial these animals are to the environment. In fact, a recent study found beavers can actually reduce nitrogen pollution by building dams

The Chesapeake Bay cleanup effort has also provided beavers with new habitat in the form of runoff control ponds and culverts, which beavers love to colonize. As more cities and town tackle pollution problems, beaver populations could even rebound further, Stephanie Boyles Griffin, a biologist with the Humane Society, reports.

🌟 Species Fun Fact: Beavers are now known to do so much for water quality that they are considered a “keystone species,” which is a species that is vital to the survival of all other species within an ecosystem.



raven washington dc potomac river

In 2016, for the first time in 100 years, a raven’s nest was spotted in the District. 

Ravens usually nest on mountain sides or cliffs, so as cities along the East Coast grew ravens left for more rural areas. But this incredibly intelligent bird is making a comeback around the Potomac and finding a home where we might least expect it — among our urban infrastructure on the undersides of bridges.

“They think they’re up on the side of a mountain face, nesting in a cavity,” Dan Rauch, a biologist with the District’s Department of Energy and Environment told The Washington Post. “They don’t know it’s a bridge.”

🌟 Species Fun Fact: Both ravens and crows are from the brainy corvid family of birds and can be tricky to tell apart. You can learn to spot the difference with this guide, but one key difference is that crows usually travel in large groups whereas ravens are seen in pairs or on their own.


Horseshoe crabs

horseshoe crab potomac river

horseshoe crab potomac river

Horseshoes crabs have roamed the earth for 450 million years. They're older than dinosaurs.

But in the last few decades as their numbers in the Chesapeake Bay and Delaware dropped, conservationists became concerned and local governments took action to protect the crabs. The hard work paid off as horseshoe crabs now swarm local beaches by the thousands.

Their return is also good news for migratory shorebirds, who rely on horseshoe crab eggs for food. This is especially encouraging news for the rufa red knot, a threatened shorebird that migrates along the East Coast in the summer.'

🌟 Species Fun Fact: Horseshoe crab blood isn’t only blue, it is very valuable to medical researchers (a quart of it can be sold for $15,000!). Luckily for these ancient creatures, a synthetic substitute is being developed to spare them from strange practice.


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