Caitlin
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Here is a wonderful article about mussels grown in tanks
A million healthy mussels
DAN KEGLEY -- Staff
Smyth County News
Thursday, April 26, 2007
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Hosts for the mussels, Redline darters are held in special tanks below which filters catch the mussels after they abandon their colorful hosts.
Dan Kegley [/FONT]
Editor?s note: This is the first of two stories.
Ospreys wheel and soar above the trees, never straying far from the river or the ponds below, calling seemingly in high-pitched glee. Kingfishers whiz past like blue darts, their rattling calls sounding like naughty laughter.
These two fish-eating birds may well be happy in the air and splashing into the waters of the Holston River?s South Fork and the adjacent Buller Fish Culture Station near Thomas Bridge. Even the ducks, turtles and geese there act as thought they know it is a special place.
Above, heaping helpings of creamy white clouds sit pretty on an endless blue platter of sky, above heavy mountains that stretch upward as though to sample them.
In the middle of it all, tucked inconspicuously near the foot of a ridge amid the acres and acres of ponds and waterways of the fish operation, the Virginia Department of Game and Inland Fisheries? Wildlife Diversity Division is doing a different kind of work. While the culture station puts, as a sign at the entrance says, fishing license dollars to work supporting sport fisheries, the Aquatic Wildlife Conservation Center is about promoting other species in the region?s fresh waters.
Of special interest are species ?of special concern,? another way of saying the animals are in some degree of trouble because of reduced populations.
Emphasis at the aquatic center is on propagating mussels, raising new generations of these freshwater relatives of clams, oysters and scallops that live partly buried in the bed, or substrate, of rivers. Healthy rivers have lots of mussels. Unhealthy rivers, well, that?s why the center exists in part, to reintroduce mussels where former conditions caused their decline.
Mussels filter the water as they sit on the river?s bottom, taking in hopefully only good, clean water. But they take in whatever is in the water as well, and when that?s toxic, it?s bad news.
The center is in the heart of mussel country. Biologist Nathan Eckert calls Southwest Virginia a ?hotspot of aquatic biodiversity,? and it is peerless in its populations of mussels. Of the world?s 1,000 mussel species, about 300 are found in United States waters, Eckert said. One-third of these mussels live in the Tennessee River system of which Smyth County?s three forks of the Holston are a part. In the rivers called Holston, Powell and Clinch, 45 mussel species are found.
That location and its facilities won it the honor of hosting overnight last fall a group of traveling mussels. The special guests were endangered oyster mussels collected from the Clinch River in Tennessee and bound for translocation into the Upper Clinch River near Cleveland Friday. They needed a place to stay between capture and release. The center is one of only a handful in the country dedicated to research, conservation and propagation of the freshwater animals.
It gets complicated pretty quickly, but here?s a short take on the mussel?s life cycle. The female mussel produces larvae, called glochidia. For each species of mussel, there is one or two host species of fish. The larvae attach to the host fishes? gills, mature a bit, drop off as subadults, and grow to maturity and reproduce, unless a predator like flatworms and hydra or raccoons and muskrats interrupts the cycle.
The biologists have gotten pretty good at propagating mussels in captivity, creating for them suitable environment indoors, filtering out nasties like flatworms from the South Fork Holston?s wholesome water that is the reason the fisheries people and the diversity people share common ground at the Buller station.
That water in all its freshness comes into the aquatic center where it swirls around in pans called rearing units, with gravel, limestone and sand and baby mussels, recreating to a high degree the riverine environment mussels need.
Working under regional non-game biologist Mike Pender in Blacksburg, the local biologists are full-timers Eckert and Joseph Ferraro and part-timers Amanda Wood and Jonathan Orr. They know how to harvest glochidia from gravid females ? those with developing young in special structures, and infest the appropriate host fish, then collect the tiny juveniles and get them started on lives of independence.
How tiny? When they drop off their host fish, mussels are ?one quarter of one millimeter in size,? Eckert said. For reference, he said, there are about 25 millimeters in an inch.
As larvae, they?re of course smaller, notable as a cloud in a beaker of water.
A larva looks a little like Pac-Man, their two shells, or valves, open. That?s about the extent of the action under the microscope. To see which ones are living, the biologists add the merest pinch of salt.
Magnified, the salt crystals look like houses compared to the glochidia. As the visible wave of salinity spreads through the water with the larvae, its tricks them into thinking a fish is present, and each little Pac-Man closes. In a real fish, the idea is to clamp down on a bit of gill tissue and hold on for a couple of weeks.
Eckert said a 50:50 ratio of living and dead larvae is good enough to go ahead with propagation in endangered species. Between 50,000 and 100,000 glochidia are released from the mother and 30 to 90 percent will become juveniles.
?We try to get as many on the fish as possible,? he said.
When the juveniles drop from their host, they are captured in a fine-mesh filer. Eckert and the others count them, placing samples in Petri dishes with grids inscribed on the bottom that helps the counters keep their place. The dishes are placed under microscopes, and a kind of census is taken.
From there they go to tanks of flowing water to sit and grow, developing rings in their shells like the growth rings of trees that can similarly be used in judging the animals? ages.
As they grow they graduate to larger rearing units, eventually getting to the big blue three-foot diameter tanks in a separate building.
About the end of May, Eckert said, the center will pass a milestone, producing its one millionth mussel. This is the center?s fifth year of working to restore mussels to the Upper Tennessee River system, Eckert said. That?s the Holston, Powell and Clinch Rivers.
?We asked, ?Can we set up a facility to being in common species of mussels and hold them long term??? Eckert said. ?We have to have natural water. After a couple of years, we saw we could hold common and endangered and then propagate the juveniles, grow them and stock the Clinch and Powell.?
Eckert knows the numbers without looking. The center produced 30,000 in 2003, 94,000 in ?04, 285,000 in ?05, and 520,000 in?06.
They?ve been in business long enough to now do recapturing in the wild of previously released specimens and get meaningful data about their survival, and ultimately of the program?s success.
One of the next projects is to try keeping host fish in cages in ponds outdoors and seeing whether their indoor success can be replicated in even more natural environs.
dkegley@wythenews.com
