Up and down the Mississippi River, people once collected tons of mussels for the pearl button industry. Factories stamped out pearl buttons from the shells, sometimes wiping out 50,000 tons of mussels annually in the early part of the last century. In recent years, the biggest threat to local mussel species has come from the zebra mussel. That invasive species came to North America in the ballast water of ships and has since disrupted many local ecosystems. Today, there’s a new effort underway to bring back local species like the Higgin’s Eye Pearly Mussel, and it’s in an unlikely place. The Great Lakes Radio Consortium’s Todd Melby has this report:
Up and down the Mississippi River, people once collected tons of mussels for
the pearl button industry. Factories stamped out pearl buttons from the shells,
sometimes wiping out 50,000 tons of mussels annually in the early part of
the last century. In recent years, the biggest threat to local mussel species
has come from the zebra mussel. That invasive species came to North America in
the ballast water of ships and has since disrupted many local ecosystems. Today,
there’s a new effort underway to bring back local species like the Higgin’s
Eye Pearly Mussel. And it’s in an unlikely place. The Great Lakes Radio Consortium’s
Todd Melby has this report:
Urban areas like Minneapolis-Saint Paul might seem like an unusual
location to boost the population of an endangered species.
But it’s here, below a busy bridge that spans the Mississippi River, that
biologists are searching for a safe place for their project. Divers have
just come up from the bottom of the river with a few mussel specimens.
“Well, we’ve got Big Toe, Maple Leaf, Three Ridge. Good enough I think.”
That’s Mike Davis rattling off the names of mussel species. Davis is
a biologist with the Minnesota Department of Natural Resources. The fact that
some mussels live in this part of the river makes Davis think that this
might be a good spot for the Higgin’s Eye. The Higgin’s Eye, which has an olive-
colored shell, has been languishing on the Endangered Species List since
Just two decades ago, this part of the river suffered from sewage runoff. The river is cleaner now and some mussels have returned. But not the Higgin’s Eye. And that has Roger Gordon worried. He’s a biologist with the U.S. Fish and Wildlife Service.
“They function as the kidneys of the river, more or less. They siphon everything that
goes through the river. They are a very good indicator species if we have a problem in the environment. They are usually the first species to get hit hard and disappear.”
For the past decade or so, it’s been the zebra mussel that’s been hitting the Higgin’s Eye. But the zebra mussel hasn’t made it to this part of the river. That’s why biologists are on a small flotilla of boats on this morning with 800 large-mouth bass. The bass and the Higgin’s Eye have a strong connection. Attached to the gills of those bass are thousands of Higgin’s Eye larvae.
“Right now, we’re counting fish in the cage. We have a known number of fish, 25 in
this case, that we’re going to place in these cages. And hopefully over the next several weeks, they’ll drop off and we’ll have clams in the river.”
Melby: “You’re putting them in the bucket?”
“Right now we’re putting them in a bucket and placing them in the cage over the
side of the boat.”
(sound of buckets banging and water sloshing)
The bass are put in cages so they don’t swim somewhere that’s not a good home for the Higgin’s Eye. In the wild, adult females mussels shoot embryos at unsuspecting fish swimming overhead.
“The larvae have a chemo-receptor in them. When they touch flesh, they actually shut. It’s a one-shot deal. If that fish clamps on a fin or an eyeball or a lip, it’s a no-go. He’s not going to develop. But if he’s lucky, and he just happens to be going through a gill arch of a fish and it’s the right fish, the right species of fish and the right size fish, it
will shut on that gill.”
But the Higgin’s Eye population is too low to leave to chance.
(Bubbling sounds of fish hatchery)
So Gordon and his colleagues bumped up the number of mussel larvae
per fish here at a federal fish hatchery in Genoa, Wisconsin. Instead of just a
few larvae per fish, the bass dropped into the Mississippi have several dozen
larvae attached to their gills.
That prep work took place inside the “Clam Shack,” which is really
just a metal pole barn that biologists built themselves.
“We didn’t have any money to do this. We scraped up and saved up at the end
of the year. We had seven or eight-thousand dollars. The hatchery guys just got together and built this little building.”
Since beginning their work two years ago, they’ve added approximately
12,000 mussel-rich fish to rivers in Wisconsin, Illinois, Iowa and Minnesota.
“We’re probably going to have to build another little building
like this. But we’ll scrape along and do what we can.”
Back on the river, Mike Davis of the Minnesota DNR calls the return
of the Higgin’s Eye historic. But with the zebra mussel closing in on native
mussel species like the Higgin’s Eye, he’s also a bit wistful.
“The former dead zone of the Mississippi may become
one of the last refuges for the Mississippi’s mussel species.”
In September, divers return to that same spot to check on the Higgin’s
Eye. They hope to find thousands of young clams nestled safely in their new
home. For the Great Lakes Radio Consortium, I’m Todd Melby.