Yellowstone has its wolves. Alaska’s Chilkat Valley has its bald eagles. And the Connecticut River has its… freshwater mussels?
The Connecticut River, specifically, the upper Connecticut River – our part of it – provides a safe haven for the dwarf wedgemussel, a freshwater mussel listed under the federal Endangered Species Act. Places that provide sanctuary for our nation’s endangered and threatened species are very special places indeed. It’s easy to imagine that all of these safe havens are far away. Far away from here, at least. National parks. Remote wilderness. Places you’ll only see on TV. But one of these special places is the big, familiar river right in our neighborhood.
Freshwater mussel shells are dull on the outside, ranging in color from yellowish to almost black. Inside, though, it’s another story. The inner shell surface (or nacre) of freshwater mussels is smooth, shiny, and opalescent. It comes in colors including white, pink, purple, bluish, salmon, and mixes of those colors. In the days before plastic, freshwater mussel shells were harvested and used to make buttons.
Dull on the outside, something surprising on the inside – that tells you almost everything you need to know about freshwater mussels.
If freshwater mussels had a lifestyle magazine, it would have to be sold in a brown wrapper. This sometimes-transgendered group of organisms has anonymous sex then abandons its blood-sucking children to a tenuous fate.
Adult freshwater mussels, as relatives of ocean-going mussels and clams, are filter feeders. Males release their sperm into the water and never meet the females that later filter it out. Females hold on to the fertilized eggs either briefly or for as long as a year.
Some mussel species are hermaphrodites, having both male and female organs. The hermaphrodite thing is an insurance policy for an organism that doesn’t play an active role in its fertilization; if no sperm should happen along, a mussel can always self-fertilize. Most flowering plants are hermaphrodites too, after all.
When the mom mussel finally lets go of those youngsters, they have only one day to find a suitable home. Freshwater mussel larvae are called glochidia (pronounced glow-KID-ee-ya). A suitable home for glochidia is within the gills of a fish. Not just any fish, but particular species of fish for particular species of freshwater mussels. The glochidia will hang on for a few weeks as parasites. They may suck a little blood, but mostly they’re hitchhikers, trying to find good habitat that isn’t next door to mom.
There are about 1,000 species of freshwater mussels in the world. Zebra mussels are freshwater mussels native to Europe and Asia, but they are distantly related to our native mussels and have a different lifestyle. North America is the red-hot center of the planet’s freshwater mussel diversity. We have over 300 species on this continent, with the southeastern U.S. being the hottest hotspot, and the Midwest a secondary one. About two-thirds of these species are imperiled.
Vermont is home to 18 species of freshwater mussels. New Hampshire hosts 11 species. Vermont takes the lead here because Lake Champlain provides a link to all that diversity in the Midwest. But New Hampshire takes a rare honor among North American freshwater mussel sites. When it comes to the federally endangered dwarf wedgemussel, “the best populations in the world occur in New Hampshire,” says John Kanter of the New Hampshire Nongame and Endangered Wildlife Program.
The dwarf wedgemussel was once found at 70 sites from Canada to North Carolina. Now, says Susi von Oettingen, an endangered species biologist at the New England Field Office of the U.S. Fish and Wildlife Service in Concord, New Hampshire, “It’s gone from Canada; disappearing from North Carolina.”
The species is down to about 20 sites. But dwarf wedgemussels are holding their own in the upper Connecticut, where there are two major dwarf-wedgemussel sites. One runs from Dalton to Lancaster, New Hampshire.
“It’s the largest population we have for this species,” says von Oettingen. “It’s almost common there.”
The other site runs from Plainfield to Charlestown, New Hampshire, or, on the Vermont side of the river, from Hartland to Springfield.
The dwarf wedgemussel is the most extreme example, but many other freshwater mussels are finding a safe haven on the northern or eastern edges of their range in New England. Von Oettingen credits relatively high water quality for this. Vigilance is needed to maintain that high quality, but surely it’s worth some effort to have the upper Connecticut River right up there with Yellowstone and Chilkat Valley as a safe haven for threatened and endangered species.