Fish help in restoration of mussel population
CHARLESTON, W.Va. -- To help restore mussel populations wiped out by two major chemical spills, West Virginia fisheries biologists have sought assistance from a few finny friends.
"Most mussel species require a fish host to reproduce successfully," said Janet Clayton, the Division of Natural Resources biologist in charge of the agency's mussel-restoration efforts.
"So, to make sure the mussels we want to restore get the fish hosts they need, we take larvae from [recently spawned] mussels and we put them in the gills of the fish."
The process sounds simple, but it's anything but.
Clayton and her colleagues first must spend untold hours snorkeling and scuba diving, probing creek and river bottoms to find mussels that have bred. Once they've captured their brood stock, they gently pry the mussels' shells open and flush the larvae out with water from a hypodermic syringe.
They then inoculate the fish hosts by allowing the fish to swim through a tank teeming with salt grain-sized larvae, or by using a syringe to inject larvae-rich water into the fishes' gills. When the larvae mature, they drop off the fish and sink to the bottom of the holding tank. Biologists collect the mature larvae and distribute them along the river bottom.
"While the larvae are living in the gills of the fish, they're essentially parasites," Clayton said. "But they don't harm the fish at all."
The propagation process is expensive and labor-intense, but Clayton said it's necessary if natural resources officials ever hope to correct the damage wrought by a 1999 chemical spill on the Ohio River near Parkersburg and a 2009 spill on Dunkard Creek north of Morgantown.
"We could try to restore damaged populations by relocating them from places where they're plentiful to places where they were wiped out, but that's just robbing Peter to pay Paul," she said. "Ideally, we'd prefer to restore populations through propagation."
It will take quite a bit of propagation to restore the mussel beds wiped out by the 1999 Ohio River spill. According to the U.S. Fish and Wildlife Service, chemicals from the Eramet Marietta metals plant in Marietta, Ohio, killed 990,000 mussels along 30 miles of river.
Resource agencies eventually reached a settlement with the company and its affiliates that earmarked $2.04 million for mussel restoration efforts. Biologists began the restoration work in 2007.
The Dunkard Creek kill, while not as far-reaching as the Ohio spill, was no less devastating. It killed everything -- fish, mussels, crustaceans and even insects.
Inspectors officially placed the blame on a bloom of golden algae, most likely created by salt-laden water escaping from a large underground coal mine.
"There was no [mussel] brood stock left on Dunkard Creek," Clayton said. "Left to its own, it would never have recovered."
Clayton and her colleagues devised a way to restore the creek's mussels and fish populations at the same time.
"Rather than spend a lot of time in [mussel] propagation, we collect our brood stock, extract the larvae, inoculate fish with them, and then stock the fish into the creek," she said. "We're also relocating some adults into the creek. We did our first inoculation and release last year, and we did one again this year."
Some mussel species can use a variety of fish species as hosts, while others require specific hosts.
"The species-specific ones definitely complicate the process," Clayton explained. "When a host fish is commercially available -- bluegills, for example -- we just raise them in one of the state's hatcheries or go out and buy what we need.
"For other species, such as creek chubs and stonerollers, we go out and seine them from creeks. One mussel species, the pink heelsplitter, requires us to go out and capture freshwater drum. So even getting the fish hosts involves a lot of work."
Restoration efforts on the Ohio have centered on nine mussel species: three-ridge, Ohio pigtoe, pimpleback, maple leaf, washboard, black sandshell, sheepnose, pocketbook and fat mucket.
"So far we've had limited success with five of those species," Clayton said.
Four species -- the creeper, giant floater, fluted shell and fatmucket -- are being reintroduced to Dunkard Creek.
Collecting larvae from breeding mussels can involve some pretty precise timing.
"There are two basic types of mussels -- long-term brooders and short-term brooders," Clayton said.
"Long-term brooders hold their larvae for several months, so they're pretty easy to collect from. Short-term brooders aren't as easy.
"We know the general time frame when their larvae become mature, so we collect some adults, put them in containers and wait for them to release their larvae. When we see lots of mature larvae, we go out and collect more adults and continue the propagation process from there."
Sometimes, though, knowing the right time isn't enough.
"Last year, [streams'] water warmed so quickly that the mussels spawned early and we just about missed our first species," Clayton said. "This year was the opposite. We got very few larvae off our first species, and the water since then has been too high to collect more brood stock."
So why go to all this trouble to restore creatures many people are unaware even exist? In a word, ecology -- the way creatures interact with their environment. Clayton said mussels are important to streams' ecosystems because they filter impurities from the water.
"A bed containing 200,000 mussels can filter a million gallons of water a day," she said. Imagine how much money we could save in water-treatment costs if our native mussel communities were restored."
Reach John McCoy at firstname.lastname@example.org or 304-348-1231.