WILLIAMSTOWN, W.Va. (AP) — “We’re in rare company,” said Tyler Hern, a biologist with the White Sulphur Springs National Fish Hatchery, as he examined a small tub containing 48 of what may be the rarest freshwater mussels in the world.
“Very few people have ever seen a shell from one of these, let alone a live individual,” Hern said, as he sifted through the gravel at the bottom of the tub to reveal additional members of the species.
A mussel as rare as its name is colorful, the purple cat’s paw pearlymussel once could be found throughout the lower Ohio River and many of its larger tributaries, including the Muskingum River in Ohio, the Green River in Kentucky and the Middle Cumberland River in Tennessee.
“Museum collections show that the purple cat’s paw was once found in the Ohio River from here to Cincinnati,” said Patricia Morrison, biologist for the Ohio River Islands National Wildlife Refuge, headquartered 2 miles upriver Williamstown, in Wood County.
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A century ago, the mussel, named for the color of its inner shell and a small protuberance on its outer shell that resembles a feline foot, was also once found in streams as distant as Illinois, Indiana and Alabama, according to a U.S. Fish and Wildlife Service fact sheet.
But the damming of the Ohio to accommodate river transportation followed by decades of virtually unregulated industrial discharge, dredging of the river bottom for sand and gravel, and the arrival of the invasive zebra mussel helped bring the purple cat’s paw to the brink of extinction.
By 1990, only two small nonbreeding populations of the mussel were known to exist — one in a reach of the Green River and the other in a section of the Cumberland River. The purple cat’s paw was placed on the federal endangered species list in July of that year.
In announcing the mussel’s endangered status, the U.S. Fish and Wildlife Service declared that, unless reproducing populations of the purple cat’s paw could be found or developed, “the species will become extinct in the foreseeable future.”
It appeared the mussel had indeed faded into oblivion, when the two known populations failed to reproduce and died. But in 1993, a biologist found the shell of a female purple cat’s paw on the shore of Killbuck Creek in north-central Ohio. The stream is a tributary of the Walhonding River, which flows into the Muskingum River and into the Ohio at Marietta, across the river from Williamstown.
During a search the following year, a small population of the rare mussel was found in the Ohio creek, but annual searches that followed the 1994 discovery either failed to turn up a trace of a population or found only tiny remnant populations that did not include females.
Then, in 2012, drought struck north-central Ohio, reducing the water level in Killbuck, and 25 live purple cat’s paws, including 10 females, were found in newly exposed portions of the creek bottom.
With the world’s only known population of purple cat’s paw pearlymussels barely numbering two dozen, while water quality in their host creek was deteriorating due mainly to agricultural runoff, “a decision was made to relocate them and breed them in captivity and not to just rely on nature,” said Michael Schramm, public outreach specialist for Ohio River Islands National Wildlife Refuge.
Biologists placed the mussels in in-stream holding cages so they could be easily found and gathered the following spring, when the females would, hopefully, be carrying larval mussels.
In 2013, six of the 10 females were bearing young in the larval stage. Three sites — the White Sulphur Springs National Fish Hatchery, the Columbus Zoo and Aquarium’s Freshwater Mussel conservation and Research Center and the Center for Mollusk Conservation in Frankfort, Kentucky — were given the task of propagating viable young mussels from the six larva-bearing females.
Three sites were used to propagate young mussels to guard against the possibility that an accident or miscalculation at a single facility would wipe out what was then the world’s population of young-bearing purple cat’s paw pearlymussels.
“We didn’t want to put all our eggs in one basket,” Morrison said.
In nature, mussel reproduction involves females releasing the mature larvae they are bearing directly into the water of their resident stream, where they attach themselves to the gills or fins of species-specific host fish — in this case, sculpins or darters — from which they receive nourishment.
After a few weeks, the larvae are transformed into young, microscopic mussels and drop off the fish to fend for themselves in the gravel and cobblestones of the stream bottom.
At the propagation sites, biologists extracted larvae from the Killbuck Creek mussels and placed them on host fish. Several weeks later, the first-ever purple cat’s paw pearlymussels propagated in captivity were born at the White Sulphur Springs hatchery. A total of 13 young members of the species survived to the juvenile stage during the first year of the captive breeding program.
The painstaking process was repeated in 2014 when more larvae-bearing mussels were found in the cage at Killbuck Creek. Meanwhile, scientists at the Center for Mollusk Conservation in Kentucky came up with a way to jump start the effort to propagate enough of the endangered mussels to begin a reintroduction program.
The Kentucky scientists had recently been successful in reproducing other species of mussels by replicating the growth medium found on host fish in laboratory petri dishes. That breakthrough made it possible to avoid the low-odds, hit-or-miss nature of mussel larvae connecting with host fish.
During the first year of in vitro propagation of purple cat’s paw pearlymussels at the Kentucky facility, nearly 100 larvae survived to the juvenile mussel stage.
“This year, they propagated over 3,000,” Morrison said.
Forty-eight mussels from the Kentucky propagation effort were taken to the Ohio River Islands Refuge headquarters on Sept. 27, where tiny green numbered identification tags were attached to their shells with a drop of glue after the shells were measured with calipers.
Measurements and tag numbers were recorded, and a bucket containing 48 of the rare mollusks was carried to an Ohio River channel a few hundred feet from the refuge headquarters, where a Fish and Wildlife Service boat was waiting.
Biologists from the refuge, the Wildlife Resources Section of the Division of Natural Resources and the White Sulphur Springs hatchery donned scuba gear and boarded the boat for a short ride to a site just off Buckley Island, one of 22 islands protected by the refuge, that was previously scouted for desirable habitat.
The divers carefully placed the mussels in small depressions they formed in the riverbottom rocks and cobbles within a GPS-recorded grid marked with metal stakes.
“We’re only putting in this many in the river today because it’s a pilot study to see how well they do within the next year,” said DNR biologist Janet Clayton. “We’ll come back next September to count and measure them to know how they’ll do from one year to another.”
If survival and growth rates are satisfactory, larger scale reintroductions can be expected, according to the biologist.
“Today is the culmination of 11 years of work from the time the Killbuck Creek population was found,” said Morrison. “For us, it’s a pretty great day.”
Information from: The Charleston Gazette-Mail, http://wvgazettemail.com.