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A bucket full of yellow/brown mussels.
Information icon Juvenile fatmucket mussels approximately 6cm in length. Photo by Chris Barnhart, Missouri State University.

There was a mussel called fatmucket…

Scientists introduce species into traditional habitats

A shelled creature called Arkansas fatmucket – yes, you read that correctly – is going to be released into a couple of Arkansas rivers this week.

The goal: baby Arkansas fatmuckets.

That bivalve’s full name: Arkansas fatmucket, a species of mussel found only in the state from which it derives part of its name. Since 1990, it has been listed as threatened under the federal Endangered Species Act.

Scientists with the U.S. Fish and Wildlife Service and the Arkansas Game and Fish Commission plan to place 120 specimens in the South Fork Ouachita and the Ouachita rivers, the mussels’ traditional habitats.

There, they hope, Lampsilis powellii will do what nature intended, and the mussel will flourish.

The species has suffered “significant population declines” in the past two decades, said Chris Davidson, deputy field supervisor with the Service’s Arkansas field office. On Tuesday, he’ll don a wetsuit and snorkeling gear to slip the mussels into pre-selected spots.

Run-off from development and dirt roads have hurt the bivalve’s habitat, Davidson said. The fatmucket thrives in relatively calm water, 2- to 4-feet deep. It prefers sandy, pebbly river bottoms –- not silted streambeds.

The mussels’ disappearance was a biological alarm, said Bill Posey, the Arkansas agency’s assistant chief of fisheries.

“They are excellent barometers of the aquatic environment,” he said.

When biologists noted that some of the mussels’ beds weren’t as heavily populated as they were in years past, they exchanged phone calls and worried emails. The species was in danger of extirpation – becoming extinct in its traditional range.

Hitching a bass ride

If you were to give human attributes to a mussel, you’d conclude that the female Arkansas fatmucket is sneaky. Once impregnated, she carries larvae of her young – but only for a little while.

While the larvae are still tiny, she dangles a wiggly protuberance from her body. A passing fish – a largemouth bass, say – that stops to investigate is likely to swim away not knowing that it’s a surrogate parent. The female mussel has spewed her offspring on its gills.

A bright green mussel dangles a fleshy white protuberance.
Arkansas fatmucket mussel lure. Photo by Chris Barnhart, Missouri State University.

The tiny Arkansas fatmuckets will get a free ride for about two weeks, long enough to mature sufficiently to live on their own. Then they drop off the fish and land on a stream bottom. Nature then takes its course.

Two years ago, scientists took over nature’s job. They collected pregnant females – the proper term is “gravid” – and took them to a facility at Missouri State University. Biologists there placed them in a facility filled with curious bass. The bass did their jobs; the larvae grew.

In the summer of 2016, the young bivalves got moved to the Kansas City Zoo, where they remained until recently. Now, biologists say, the mussels, each in shells about 2-3 inches long, are ready to return to the waters from which the species sprung.

Biologists have selected sites where they believe the mussels will thrive. That leads us, dear reader, to a rhyme suitable for scientist and layman alike:

There once was a mussel called fatmucket
That biologists placed in a bucket.
“The species ain’t dead,”
The scientists said,
“So into the water – chuck it!”

Contact

Mark Davis, Public Affairs Specialist
mark_r_davis@fws.gov, 404-679-7291

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