In search of a tiny fish known as the Maryland darter, scientists have donned snorkels and scuba tanks. They’ve dragged nets, even electrified ones, through ice-cold waters of the Susquehanna River and its creeks, and yet turned up no trace of a creature not seen since 1988.
During hundreds of hours of searching since that sighting, they’ve used any method they can think of to detect what is said to be the only animal species that can’t be found anywhere except Maryland.
Now, they’ve decided, it likely can’t be found anywhere at all.
A process to declare the Maryland darter extinct is expected to begin next year.
Its story, perhaps nearing an end, is one that ecologists say explains a lot about the Chesapeake Bay at large.
While its disappearance may not have caused visible ripples in the northern Chesapeake waterways that were its home, the Maryland darter was one part of a diverse and unique web of wildlife. Though the fish were easy to miss — both because they were few in number and each no more than 3 inches long — they were no less integral to vibrant stream and river ecosystems, feeding on snails and fly larvae while serving as food for bass and eels.
But stressors, nearly as imperceptible as the darters themselves, were too much for its small numbers to bear. Waters clouded by sediment and algae, a product of development and agriculture on nearby lands, became less hospitable to darters and their prey. The darters became so few in number that something like a big storm may have become enough to knock out entire generations of a fish with a life span of only a few years.
Richard Raesly, a Frostburg State University professor who is the preeminent expert on the Maryland darter, said the tragedy makes him think of a fable known as the rivet-popping hypothesis. Posited by the ecologists Paul and Anne Ehrlich in 1981, it suggests that the variety of species in an ecosystem is as important as rivets on the wing of a plane: Take out a few, and the craft still flies.
“But if you keep taking them out, eventually there is going to be a failure,” Raesly said. “The disappearance of one species or two species might not cause an ecosystem to collapse, but it is indicating that the health of the ecosystem is declining.”
For now, the most sensitive species are the ones at risk. But others could be next, ringing an alarm bell for those like Scott McDaniel, executive director of the Susquehannock Wildlife Society in Darlington.
“It’s kind of a heartbreaking event when you’re losing something that’s been here long before humans were ever on this landscape,” McDaniel said.
The Maryland darter was so unique to waterways like Deer Creek in Harford County, where it was last seen, that it embodied this spot of earth, he said.
“And now it’s gone.”
The Maryland darter was only ever known to inhabit a narrow corner of the ninth-smallest state. From the 1960s through the 1980s, scientists captured about 100 specimens in steep, fast-flowing, rocky and gravelly sections of the lower portions of tributaries to the Susquehanna River.
A relative of the yellow perch and walleye, it appears unremarkable, its sandy-colored scales speckled with brown spots.
But it became a priority for conservation in the 1960s, after survey results warned the Maryland darter population was dangerously small. In 1967, it was added to the federal list of endangered species.
That triggered a series of searches for the darter. Under the designation, a review of the species’ health and abundance must take place at least every five years, at which point its place on the endangered species list must be reconsidered.
Repeatedly, fruitless surveys meant the Maryland darter remained on the list. There was some hope, along with some fear the worst might be happening.
“Rare species, if you don’t find them for a year or two and you say they’re extinct, they have a way of coming back,” Raesly told The Baltimore Sun in 1991. “But at this point the outlook is very poor indeed, and if I don’t get any throughout the rest of this summer and into the next spring, I think I would have to say they have probably gone extinct.”
Despite that outlook 30 years ago, Raesly and colleagues weren’t ready to give up. The next — and what was thought to be the last — series of searches for the darter took place from 2008 through 2012, and involved hundreds of man hours and a long list of strategies.
They snorkeled. They trawled, dragging nets from behind a boat. They seined, using a net that hangs vertically in the water to trap fish. They tried electrified equipment, which sends a shock through the water that is harmless but brings fish to the surface, making them easier to spot or catch.
They surveyed at different times of year, wondering if the darters might be easier to find in the winter, when such wildlife searches aren’t usually conducted. They searched waterways where the fish had been seen in the past, and where they hadn’t, but could find similar habitat: Deer Creek, Gasheys Run, Swan Creek, Octoraro Creek and the main stem of the Susquehanna itself.
The most recent effort, which began in 2020 and wraps up this year, cost close to $50,000. That is a larger than usual price tag that reflects just how difficult the search has been, and how thorough, said Julie Slacum, manager of strategic resource conservation at the U.S. Fish and Wildlife Service’s Chesapeake Bay office in Annapolis.
Still, no Maryland darters turned up, though five other darter species were present. A statistical analysis suggests the pursuit has been so thorough that there is a less than 1% chance the species survives but has evaded search efforts.
Raesly was the last person known to have laid eyes on the fish, during a 1988 survey of Deer Creek, a rocky river that stretches across northern Harford County and empties into the Susquehanna about halfway between the Conowingo Dam and Interstate 95. He said the distinction gives him some pride — like that of a birder who has spotted a rare variety — but mostly sadness.
“There’s always that thrill of discovery when you step into a stream and you wind up locating something that even other biologists ... rarely encounter,” he said.
What the scientists say is one last effort now is expected to end this year. Unless any turn up this time, the Maryland darter’s extinction is all but official: the federal wildlife Service has proposed removing the species from its endangered list. That regulatory process is set to begin next spring.
If there is a silver lining to the Maryland darter’s demise, it is that it could help intensify efforts to conserve other vulnerable animal species. Removing one species from the endangered list means more resources for the others.
Ideally, that happens because a population has rebounded from the brink, though, Slacum said.
“This is not what we hope for,” Slacum said. “We hope to recover species.”
One such vulnerable species is the bog turtle. Another is the Chesapeake log perch, a fish with a similar range as the Maryland darter, but that extends up the Susquehanna into Pennsylvania. Conservation measures to save them would be similar to those employed in hopes of protecting the Maryland darter and many other species, such as improving forested buffers around streams to catch pollution and sediment that would otherwise flow into waterways.
While dedicated searches for the Maryland darter aren’t expected to continue beyond 2021, scientists will continue looking closely for them in state waters. Jay Kilian leads those efforts as a biologist with the Maryland Department of Natural Resources, conducting the Maryland Biological Stream Survey across the state to assess the health of waterways and the abundance of life within them.
The survey samples some 250 streams a year, a reach that most certainly covers suitable habitat for the Maryland darter, he said. It’s a nice insurance policy to ensure biologists are on alert for the darter’s possible reemergence, though Kilian said he believes if the fish were out there, he would have seen one by now.
Still, when it comes to rare wildlife, hope is hard to lose. Though the Maryland darter became the target of study and conservation in the 1960s, it was actually discovered in Swan Creek some 50 years earlier. It swam for all those decades completely undetected by scientists, despite efforts to find it again.
Another darter species, the stripeback darter, was once thought to have vanished from Maryland waters (though it remained in at least one other state). But it reappeared in Maryland in the 1990s after 50 years of being considered missing.
Could the Maryland darter be alive, just in a similar stretch of elusiveness?
Kilian said it’s unlikely, but always possible: “It’s really hard to prove the absence of a species.”
Baltimore Sun librarian Paul McCardell contributed to this article.