The Maryland darter, one of the rarest fish in the world, has been missing in action for 33 years. Now, it is headed to the extinction list. The impending move comes after one last intensive “fish hunt” by Maryland wildlife officials and private groups this summer and fall. The hunt focused on several tributaries of the Susquehanna River, where Maryland darters have been known to live, as well as a few streams and creeks that seemed to have suitable habitat.
The fish was the only animal of any kind known to be found solely in Maryland.
In the largest search ever mounted for a Maryland fish, crews repeatedly used snorkeling, seining, water shocking and even bottom-dragging electric trawling nets — all with no success.
Unfortunately, the use of eDNA, a recent breakthrough technology for sleuthing out the presence of rare or elusive fish and animals without actually catching it, could not be used for the Maryland darter. That’s because all known preserved specimens were originally kept in formaldehyde, which damaged their unique DNA markers.
“Yeah, it’s almost certain that it is extinct,” said a downcast Rich Raesly, a biology professor at Frostburg State University who was the last human to see a Maryland darter — in Deer Creek below the Conowingo Dam in 1988. Raesly and his students have looked for another in vain ever since.
Even Jay Kilian, who for some 13 years has coordinated multiple search parties for the darter for the Maryland Department of Natural Resources, is almost ready to throw in the towel. “There are many examples of rediscoveries of species previously declared extinct,” he noted, but added that the empty results from the recent survey mean the possibility of a Maryland darter still swimming somewhere “is very, very low.”
One faint remaining hope is that a tiny population of darters may still inhabit the Susquehanna’s mainstem, which is all but impossible to sample.
The U.S. Fish and Wildlife Service, which has already prepared a draft order declaring the Maryland darter extinct, says there is only a 1% chance that the fish was missed in the last great search, which was to continue into early November.
What caused the blinking out of the darter, a 3-inch fish that dined on snails and caddis flies and sported a dark V-shaped saddle and blotches of tannish-brown? According to an evaluation by the USFWS, the largest factors are decreasing water quality from farm runoff and fluctuating water levels created by the nearby Conowingo Dam.
A native star is born
In 1912, two biologists from Cornell University doing a federal survey of ray-finned fish in the Chesapeake Bay were seining in Swan Creek, a fast-flowing stream in the upper reach of the Bay near Havre de Grace.
“On a long, stony riffle where the bottom was comparatively free from boulders and the current so swift that one would not have expected to find fishes of any kind,” a pair of small fish with “a very striking appearance” danced in their seine nets.
Nobody had ever seen one. Lewis Radcliffe and William Welsh gave it the scientific name Etheostoma sellare and the common name Maryland darter. But the fish immediately showed itself to be extraordinarily elusive. No sooner had the scientists announced their discovery in a scientific journal then it disappeared — for 50 years.
In 1962, the darter was “rediscovered” when yet another Cornell contingent, researcher Leslie Knapp and his students, found an adult female concealed among a school of tessellated darters in Gasheys Run, a Swan Creek tributary. The finding sparked a flurry of new efforts to find the fish that lived in the fast lane of strong riffles.
Another was found in the stream three years later. That same year, darters were found for the first time farther north in Deer Creek, a fast-moving stream that flows into the Susquehanna River below the Conowingo Dam. From then until the last one was observed in 1988, only Deer Creek yielded darters.
In a heyday of sorts, between 1965 and 1977, Knapp, Raesly and their students observed 77 Maryland darters.
Recognizing the scarcity of the fish species, the Maryland darter was declared federally endangered in 1967. Despite new protections afforded by the listing, the bottom dropped out again; only 25 were recorded between 1978 and the last sighting in 1988.
The Maryland DNR launched a plan to help the darters rebound by capturing and reproducing them in captivity. But before the project could get off the ground, the darters were gone.
The lower portion of Deer Creek was designated a critical habitat by the USFWS in 1984. Many farmers signed easements when approached by the Deer Creek Watershed Association to protect the shoreline, and Harford County officials restricted development in the area.
But there also was pushback. In 1995, the Maryland Farm Bureau asked the USFWS to declare the darter extinct to remove land use restrictions. The agency denied the request.
Meanwhile, the state deployed major search efforts from 2008 to 2010, in 2012 and again in 2020. Raesly continued to take his students on watery searches on his own.
But no darter was ever seen again.
The last darter
Raesly’s first encounter with the Maryland darter was in 1986 as a grad student at Penn State, which put him in charge of surveying for the fish.
One day in 1988, wearing a dry suit to stay warm while snorkeling in Deer Creek, he spotted one behind a boulder, lying on the bottom.
He and the fish watched each other for about 20 minutes. “At that time, I never thought it would be the last one I would ever see. It saddens me,” Raesly said of what was likely the last sighting of a Maryland darter on Earth.
The realization also instilled in him a determination to see things before they are gone. His family has taken vacations to
show their 17-year-old daughter creations that may also slip away: orca whales in the San Juan Islands and glaciers in the Canadian Rockies.
Collected to death?
Official records show 106 Maryland darters collected between 1912, when it was discovered, and 1988, when Raesly swam with the last one. It also is known that there are about 80 of the fish preserved in museum and university collections.
That gives rise to a question: Was the darter already on the brink of extinction and then pushed over the edge by scientists and collectors?
Raesly never kept any of the darters he found. Sacrificing 80 of them for scientific purposes over 76 years should not be blamed for the species’ end, he said. In retrospect, Raesly said that Maryland darters were likely well on their way to extinction for other reasons.
“It may have been a factor in their ultimate demise, but a number of water-quality factors prior to that started them on the downward trajectory,” he said.
According to records, most of the Maryland darters kept for preservation were collected by Knapp, the Cornell researcher who “rediscovered” the fish in the 1960s. He later worked for the Smithsonian Institution and wrote seven studies on darters of various species before dying in 2017.
Raesly noted that scientists typically retain a number of “voucher” specimens of a new species to document them. It wasn’t until 1975 that Maryland officials started requiring permits for keeping a darter.
But not all specimens were kept by scientists. For example, one of two Maryland darters at a University of Florida museum was donated by relatives of a private collector.
Kilian of the Maryland DNR expressed similar sentiments that the Maryland darter was likely doomed, with or without some of its members sacrificed for history. “Back in the day, preserving everything you caught was common practice among ichthyologists across the country. This led to many species’ descriptions and built the great museum collections that we have today,” he said.
“It is true that removing over 70 individuals from what was at the time probably a small population certainly didn’t help things. Of course, Knapp didn’t know that at the time. One could make an argument, though, that a species with a population that small was probably doomed to extinction even without that added collection pressure.”
The usual suspects
The USFWS evaluation of the Maryland darter in its draft extinction order cites, above all, changes to water quality and quantity in streams where the fish was known to live.
Pollution from agriculture and development runoff was listed as the main cause of declining water conditions needed by the darter to survive.
Sediment from erosion and runoff not only reduced water quality but also may have smothered darter eggs on the stream bottom.
Erratic water levels likely contributed as well. The Conowingo Dam, which was built in 1929, created several unfavorable conditions for the Maryland darter, according to the evaluation. Fluctuating water levels during power production created sedimentation problems and sometimes stranded fish in pools, which could get too warm for them to survive and increased predation by other fish.
“It is likely that the impacts from the Conowingo Dam and agricultural land uses reduced the Maryland darter to small, isolated subpopulations,” the USFWS evaluation said. “This likely made it more sensitive to even minor disturbances resulting from incremental increases in urban development, chronic inputs of sediment and nutrients from agriculture, and alterations in water flow.”
Increased predation may also have been a factor. With the creation of the Conowingo Dam, large predators such as eels could no longer continue upriver and may have made forays into downstream tributaries, eating darters.
Other possible negative influences include rising temperatures from climate change and water withdrawals for drinking and irrigation.
Clearly, the Maryland darter occupied a small niche of the Earth. It was not a major food source for other species. Does it matter that it is gone?
Yes, Raesly argued. “Every spot is unique. Many of those living things are often small and not noticed by man, but the fact is they do make a place unique. It’s a huge loss to humanity whether we are talking about rare alpine plants on Mount Washington in New Hampshire or the Maryland darter.”
Cover photo: Anastasia Simpson snorkels in Deer Creek, a Maryland tributary of the Susquehanna River, as part of an unsuccessful effort to sight a Maryland darter. (Dave Harp)