Pearls of the Gasconade
Sue Bruenderman and Scott Faiman float face-down in the chilly waters of the Gasconade River. Outfitted in wet suits and snorkeling masks, the Conservation Department researchers are doing what looks like a crawdad crawl along the streambed. Even though they wear weighted diving belts, they struggle to keep from being swept away by the swift current. Both run their hands along the bottom hoping to find mussels that have burrowed into the gravel.
Suddenly Bruenderman is on her feet, wavering as the water surges against her legs. She has pushed her snorkel mask onto her forehead. Cupped in her hands are nine brownish mussels, each one no bigger than a penny. If you're hunting for mussels, finding this many live ones seems like a good start. "They're Asian clams," says a disappointed Bruenderman, who is the state malacologist, an expert on mussels. As Missouri's native mussels have declined, this adaptable exotic species has flourished and competes with native species.
Minutes later Faiman, a fisheries research assistant, comes out of the water with better news. "I've probably seen 40 mussels," he says, hoisting his mesh bag full of the specimens he's collected. He reels off the list of species--pocketbooks, muckets, purple wartybacks and ellipses.
Despite Faiman's good luck in this spot, mussels are at the leading edge of an alarming decline hitting mussels and other aquatic animals native to Missouri--fish, crawfish, amphibians and semi-aquatic reptiles. Similar trends are reported nationwide. If the trend isn't reversed, more than a few will almost certainly disappear from the state or vanish into extinction.
Highly tolerant species, such as the Asian clam, are thriving. Others that make up much of the state's native aquatic fauna are increasingly threatened. Today, approximately 28 of Missouri's 65 mussel species are rare or declining and vulnerable to disappearing from the state.
Mussels are an important link in the food chain along the stream. Muskrats, otters and raccoons feed on them, as do some fish species. Mussels also filter water through their gills, storing sediment and contaminants in their bodies and shells. They can be thought of as nature's vacuum cleaners. They also are an important indicator of habitat and water quality. Water quality affects not only stream life but also public and private water supplies statewide.
Missouri's aquatic fauna is rich and distinctive. Few other states can boast of having two of the continent's greatest rivers and the diversity of stream organisms Missouri has. The web of life those streams sustain is diverse. All aquatic animal species, including 65 species of mussels, rely on clean water and suitable stream conditions to survive. Simply put, Missouri has much to lose if aquatic life declines.
Bruenderman and Faiman's field work here on the upper Gasconade is crucial to addressing the plight of mussels. Their study on the Gasconade and other rivers will be a blur of long days on the river and analyzing data back at the Conservation Department's Conservation Research Center in Columbia. Their research may influence everything from land management practices to endangered species policy. Such scientific work is slow and often tedious. Biologists will tell you that nature seldom reveals its secrets to the impatient or lazy.
The pair also is studying mussels in the Meramec and Little Black river basins. Today they are working just upstream from the Conservation Department's Schlicht Springs Access, about five miles south of Crocker in Pulaski County. Historically the Gasconade has harbored stable populations of about three dozen mussel species. It's also home to a number of those in trouble, including the sheepnose, scaleshell and elephantear.
The Gasconade provides a glimpse of the wider problems facing mussels. Within minutes of launching their boat, Bruenderman and Faiman are eye to eye with one of the problems. A black Angus cow is standing belly-deep in the river. "You'll see whole herds of cattle in the tributaries of the Gasconade," Bruenderman remarks. Cattle trails denuded of all grass crisscross the bank. Cattle increase soil erosion and damage habitat when they wade in streams. Their waste also adds nutrients that increase algae blooms and deplete oxygen in the water, harming or killing aquatic animal and plant life.
Along this section of the Gasconade, the right bank is covered with sycamores, cottonwoods and other growth that stabilize the bank. Treeless grazing pasture runs right up to the bank on the opposite side. Where pasture and river bank meet there is only a sheer 15-foot wall of exposed soil. Eroded soil is clearly pouring into the stream. "Odds are you aren't going to find many mussels there," Bruenderman says.
Such disturbances are gradual in their harmful effects on populations of mussels and other aquatic life, including fish that host mussels in their microscopic larval stage. "As more and more of the watershed is disturbed, you get gravel movement." Bruenderman explains. "The gravel comes down and fills in areas where there is diverse habitat. Where you had a mix of riffles, pools and holes it becomes homogeneous. The species that depend on those niches get pushed out." Specialized niche species--those that account for so much of Missouri's natural diversity--lose out to the generalists, the Asian clams and others better able to adapt.
Bruenderman and Faiman again head upstream in their 18-foot boat. Faiman opens the throttle on the 45-horsepower motor, causing the boat to buck slightly against the swift current. He eases the boat up to a long gravel bar. Bruenderman jumps out and disappears into a thick stand of sycamores and willows. Debris stuck in low-lying tree forks shows where high water has come and gone. It's a good place to find mussel shells.
In no time, Bruenderman cradles a dozen or so in her hands. "If we find shells, we know that now or at some point the site supported that species," she says. "We can also use it as an indicator of whether that site would be a good candidate for reestablishing a mussel community." Middens, places where muskrats or raccoons dined and left behind piles of shells, can serve the same purpose. Today, however, they often contain more Asian clams than native species.
Both biologists have hopes today of finding one of the state's rarer mussels--the snuffbox. It's part of the same genus that includes Curtis' pearlymussel, a species that mussel experts now concede is likely extinct. That makes the snuffbox the last of its genus in Missouri. The swift water of this riffle would be a good spot to find them, but the odds are against it. They have never been found in the Gasconade. Old males have turned up in the Meramec, but there are few signs the species is reproducing there.
Faiman returns to the water as Bruenderman searches the bank for more shells. Moments later he is once again doing the crawdad crawl along the bottom, his hands probing the streambed. He splashes to his feet and eagerly turns a mussel over and over in his hands. "I just found a scaleshell," he reports. It's a significant discovery. The U.S. Fish and Wildlife Service is considering the rare scaleshell for protection under the Endangered Species Act.
The scaleshell has declined across its range, leaving Missouri as its last stronghold. "We have the best population of them left in the country in the Meramec," Bruenderman explains. "We're seeing them here in the Gasconade as well." She comes close for a look as Faiman pulls out calipers to measure the shell and determine its age. Minutes later he gingerly returns the mussel to its watery home. Earlier in the day Faiman also released an elephantear mussel he discovered.
It's near the end of another day on the Gasconade, and Faiman eases the boat downriver. To the biologists' trained eyes it's been a day of sharp contrasts. They documented degraded stream habitat, but they also found positive signs in the number of species they turned up. They also found sizable pockets of stable habitat, places where mussels could thrive. And they verified that the Gasconade still sustains two of the state's rare mussels.
WHAT can you do?
- Intensive urban development increases runoff and water velocity, which worsens erosion and changes stream channels. Get involved with your local zoning board and city council to protect or improve stream quality.
- Avoid or minimize your use of lawn chemicals--fertilizers, herbicides and pesticides. If you use them, follow the directions for mixing and application. Remember, runoff pollutes local streams and groundwater.
- Control erosion from construction sites with silt fences and silt catch basins.
- Fence livestock at least 100 feet from the stream on each bank. Overgrazing kills vegetation that holds the soil in place and filters runoff water.
- If you're farming bottomland or planning watershed development, allow for a forested buffer along the streams. Look into the growing number of economicaly feasible agricultural alteratives, such as growing ginseng or walnut trees.