Monday, November 8, 2021

Goodbye Maryland Darter, We Hardly Knew You

Because there were never very many of you to begin with: The long goodbye to the Maryland darter - Fish to be declared extinct after final search comes up empty (Bay Journal)

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.

Maryland Darter

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.

Deer Creek, Maryland

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.
MD biologist looks for darter

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.

There are lots of successful darters, and more than a few examples of extremely rare and endangered darters. See "Snail Darter" if you don't remember the controversy. While I'm sure some factor in their ecological niche determines whether a species like this is widespread and resilient to land use changes, or highly localized, and vulnerable to changes in its habitat. 

Here's hoping the Maryland Darter manages to elude scientists for many more years, and then emerges again, and blows them a raspberry.

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