Kentucky may best be known for its bluegrass, but the state’s lakes and rivers are also home to a number of threatened fish and shellfish species that contribute to such worldwide industries as cultured pearls and caviar.

Three Tennessee Tech biologists are studying freshwater organisms in the state to learn more about the reasons for their declines.

Phillip Bettoli tracks paddlefish movement in Kentucky Lake by working with commercial fishers who net for the caviar-producing females. Jim Layzer monitors the effect of dam-regulated water flow on mussels in the Green River, and Hayden Mattingly analyzes blackside dace minnow populations for possible migration patterns.

Bettoli’s paddlefish project. After a collapse of Eurasian beluga sturgeon, Mississippi River basin paddlefish have been substituted as an international source for caviar, and Biology Professor Phillip Bettoli’s project aims to determine the extent of over-fishing to find out if current state regulations are sufficient to protect Kentucky Lake paddlefish populations.

Fisheries biologist Phillip Bettoli, right, and a Kentucky Lake paddlefish. With him on the trip was a biologist from the Tennessee Wildlife Resources Agency, left, and a commercial fisher, center.

“Paddlefish were once common throughout the 22-state Mississippi River basin, but their range has shrunk and populations have declined in most locales either because of over-fishing or destruction of their natural habitat,” says Bettoli, a Ph.D.-level research scientist with the U.S. Geological Survey whose work is stationed on campus.

Although the Kentucky Lake population seems to be relatively abundant right now, his study shows signs that it too is being significantly over-fished.

“We’ve discovered that the population is exploited at unsustainable rates during periods of average or below average rainfall, when river flows are low and commercial fishers can easily deploy their nets,” he says.

His study has also found that the percentage of paddlefish catch actually harvested by the commercial fishers is less than 10 percent. The rest — more than 90 percent — is considered “by-catch” that is simply returned to the water.

“Any non-targeted organism that encounters fishing gear is referred to as 'by-catch.' Dolphins caught by tuna fishers are by-catch, for example, and so are sea turtles caught by shrimp fishers,” explains Bettoli.

In the case of paddlefish, by-catch refers to the immature of either sex and adult males of the species — in other words, those that don’t produce eggs for the much-coveted caviar.

Bettoli’s project — in addition to recording many other factors — monitors the initial and delayed mortality rates of the by-catch paddlefish.

Initial mortality rates are easy to determine because that simply means counting the number of fish that are already dead when they’re removed from the nets, but delayed mortality rates — the number of paddlefish that die after being released back into the water — is somewhat more difficult to track.

Attaching a radio tag to a captured paddlefish.

For that, Bettoli and his research assistants attach radio transmitters to the fishes’ bodies to monitor their movement for several days — and that’s not always an easy task, he says.

“A few days ago, when it was pretty cold and rainy, we were out on the water tracking radio-tagged fish to see who lived and who died after being released the day before,” he says. “We’re currently tracking a batch of 18 fish, and most are still alive.”

In addition to a passion for the project, Bettoli’s sense of humor helps get him through the rainy days. “After many years of careful research, we’ve determined beyond a shadow of a doubt that dead fish don’t swim upriver,” he jokes.

Layzer’s mussel research. Biology Professor Jim Layzer — who, like Bettoli, is a Ph.D.-level research scientist with the U.S.G.S. and stationed at TTU — has studied what he calls "living rocks," freshwater mussels, for 17 years.

Although mussels can live for decades, they make no sound, can’t see and seldom move from their secure spots, usually burrowed into river bottoms — but in spite of their humble characteristics, they have incredible adaptations for reproducing and serve an important function in the cultured pearl industry of Japan and other nations.

Varieties of mussels found in Kentucky Lake.

“Small pieces of mussel shell are used as implant beads in oysters to start the growth of cultured pearls in Japan and other nations, and Tennessee commercially harvests — primarily from Kentucky Lake — more freshwater mussels than any other place worldwide,” Layzer says. “No other country in the world equals the variety of freshwater mussels found in the United States. Europe has only 12 different species, but there are about 300 different species here, most of which are native to the Mississippi River watershed."

Of those 300 species, however, as many as 70 percent are endangered, threatened or extinct and in need of special protection, according to the U.S. Fish and Wildlife Service.

To help protect the varieties of freshwater mussels living in Kentucky’s Green River, Layzer has been working with The Nature Conservancy since 2000 on a research project to develop and test a conservation regime that can be used by the U.S. Army Corps of Engineers to regulate water flow through the river’s dams.

“The basis of my research is monitoring how the mussels respond to this new discharge regime,” he says. “During times of unusually heavy rains, those dams hold the excess water in reservoirs. Then it’s released over an extended number of days, creating a river flow that’s somewhat abnormally high for the season — and while that’s great for flood control, we’ve found that practice seems to harm mussel populations more than an actual flood would."

That’s because mussels generally reproduce the same way they “eat” — by siphoning microorganisms like plankton and sperm from the male species into their shells, thus fertilizing the female’s eggs. Far from looking like their parents, however, infant mussels are born as larvae that must live on the body of a “host” fish for several weeks until they reach maturity and drop to the river bottom.

“But the high flows in the Green River prevent the juveniles from dropping off their fish hosts as they should, and many wind up in unsuitable habitats, where they die,” Layzer says.

Certain mussel species depend on certain fish species to serve as hosts too, so the vitality of the host fish populations has a direct impact on mussel populations.

“In fact, my ongoing research seems to indicate that no single factor is responsible for declining mussel populations in regulated rivers,” he says. Other factors threatening freshwater mussels, he concludes, are pollution, sedimentation, habitat loss and dams that discharge cold water. Although the dams on the Green River don’t discharge cold water, Layzer says his research at other locations indicates that the number of juvenile mussels are much lower below the discharge.

Mattingly’s minnow monitoring. While some people like to spend lazy afternoons catching minnows from small, shaded streams, Biology Assistant Professor Hayden Mattingly is involved in a research project — funded by the U.S. Fish and Wildlife Service — to monitor the movement patterns of blackside dace minnows.

The tiny blackside dace.

Native to only eight southeastern Kentucky counties and three northeastern Tennessee counties, the minnows spawn from April to July in silt-free, gravel areas in the upland streams of forested areas.

“Anything that contributes large amounts of silt to the streams where blackside dace live — it could be agricultural runoff, mining and logging practices, highway or dam construction or any other number of activities — could also affect the fish,” Mattingly says.

Because the fish’s natural range also coincides with the coal-rich region of Tennessee and Kentucky, surface mining is believed to have a significant impact on its population, according to one wildlife conservation web site.

Rather than trying to determine what factors are contributing to the blackside dace population decline, however, Mattingly’s research monitors the minnows’ movement patterns for signs of migration.

Biologist Hayden Mattingly, right, and student Jason Detar count blackside dace captured from a forest stream.

After gathering data from 72 sites within 28 streams, Mattingly and his research assistant used backpack electrofishing — which brings the fish to the water’s surface for counting — to estimate blackside dace populations.

“We studied two streams for about a year, looking at each one every six to eight weeks, to track movement patterns, and we found that about 60 percent of the population in one stream was highly residential, while about 80 percent of the population in the other stream was residential,” he says.

That means a sizeable minority of the fish have likely dispersed and migrated to other parts of the stream or to nearby tributaries, and that is a positive sign.

“Although the majority of blackside dace seem to spend their lives in the tributary where they were hatched, it’s healthy for a portion of the population to migrate because that increases the gene flow, which is generally positive for any species,” Mattingly says.

The next step of his research is to try to learn how far and how many blackside dace actually are migrating and use that information to create a dispersal model to show what percentage of the population might relocate to any given stream.

“The farther the relocation, the lower the percentage of successful migrations, of course.”

Mattingly says he hopes his research findings can be used to make better-informed decisions regarding species conservation.

“When you’re directly involved in this type of research, you really come to understand how important it is that we as a population must focus on how to meet our own needs in ways to keep natural habitats healthy for native animal species,” he says.