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A combination of predators, water temperature and disease may be responsible for easing the fears of an overpopulation of an invasive species of mussels in Lake of the Ozarks.
The Missouri Department of Conservation has been tracking the progression of the zebra mussel since it was introduced to the lake about five years ago. Once the mussels took hold, the population was reproducing rapidly, causing concerns about the long term impact of the species. But for the last two years, MDC fisheries biologist Greg Stoner says there are signs it may be slowing down.
For the second year in a row, Stoner said he is seeing fewer and fewer zebra mussels on the lake and downstream from Bagnell Dam on the Osage River. The zebra mussel reproduction appears to have peaked and is now on the decline.
About three years ago, Stoner said the mussels had established a good population from below the Bagnell Dam on the Osage River downstream and upstream to the Gravois Arm.
Reports of colonies the mussels attaching themselves to boats, docks and rocks were common, he said.
Now in some areas the numbers have significantly declined or disappeared altogether.
“Two years ago, areas that were covered are now rid of the zebra mussels,” Stoner said. “We are seeing a trend and that’s good news. We think one factor is the water temperature. We can reach water temperatures on the lake into the 80 and 90s. Those temperatures cause stress on the mussel.”
Stoner said an area under the State Highway 5 bridge in Gravois Mills is the only area he has found so far where the mussels seem to be reproducing. He believes a nearby spring keeps the water temperature on the cooler side.
Disease may also be a factor. When zebras congregate in a colony, they are clustered together or packed tightly, he said. If there was some kind of disease, it would spread rapidly and kill off large numbers.
Stoner said natural predators also seem to be doing their part to help with the efforts to rid the lake of the mussels.
Several species of native fish which usually feed on shad seem to prefer the zebra mussel or “junk food” as it is often referred to. The blue cat and drum are feeding on the adult mussels, reducing the reproduction and aiding in the decline.
When an invasive species moves in there is often a population explosion, he said, they fill a niche not being being filled by a native species, but in time they overshoot the carrying capacity of the environment. Something is missing that slows down their reproduction.
A combination of predators, water temperature and disease may be responsible for easing the fears of an overpopulation of an invasive species of mussels in Lake of the Ozarks.
The Missouri Department of Conservation has been tracking the progression of the zebra mussel since it was introduced to the lake about five years ago. Once the mussels took hold, the population was reproducing rapidly, causing concerns about the long term impact of the species. But for the last two years, MDC fisheries biologist Greg Stoner says there are signs it may be slowing down.
For the second year in a row, Stoner said he is seeing fewer and fewer zebra mussels on the lake and downstream from Bagnell Dam on the Osage River. The zebra mussel reproduction appears to have peaked and is now on the decline.
About three years ago, Stoner said the mussels had established a good population from below the Bagnell Dam on the Osage River downstream and upstream to the Gravois Arm.
Reports of colonies the mussels attaching themselves to boats, docks and rocks were common, he said.
Now in some areas the numbers have significantly declined or disappeared altogether.
“Two years ago, areas that were covered are now rid of the zebra mussels,” Stoner said. “We are seeing a trend and that’s good news. We think one factor is the water temperature. We can reach water temperatures on the lake into the 80 and 90s. Those temperatures cause stress on the mussel.”
Stoner said an area under the State Highway 5 bridge in Gravois Mills is the only area he has found so far where the mussels seem to be reproducing. He believes a nearby spring keeps the water temperature on the cooler side.
Disease may also be a factor. When zebras congregate in a colony, they are clustered together or packed tightly, he said. If there was some kind of disease, it would spread rapidly and kill off large numbers.
Stoner said natural predators also seem to be doing their part to help with the efforts to rid the lake of the mussels.
Several species of native fish which usually feed on shad seem to prefer the zebra mussel or “junk food” as it is often referred to. The blue cat and drum are feeding on the adult mussels, reducing the reproduction and aiding in the decline.
When an invasive species moves in there is often a population explosion, he said, they fill a niche not being being filled by a native species, but in time they overshoot the carrying capacity of the environment. Something is missing that slows down their reproduction.
“I have had a monitor under a dock in South Buck Creek at what was the epicenter of the zebra mussel infestation, last week there was not a single live mussel,” he said. “We definitely need to continue to be viligent, we probably will never be rid of them and the population may fluctuate. We may have cool summer and see an increase in production. Then a hot summer then knocks them back down. Once the mussels are here, the concern is hauling them to another waterway and introducing them into an environment where they would thrive."
About zebra mussels
According to the Missouri Department of Conservation, once the zebra mussels arrive, there is no affordable way to get rid of them. They pose a serious threat not only to boats and structures on the water but to native mussel species. Once eggs are laid by adult mussels, the species spreads.
There’s no question the mussels can survive in the lake and create havoc for the environmental balance of the water, cause extensive damage to boats and docks and if reproduction flourished pose a threat to the operation of Bagnell Dam.
The small mussels adhere to boats, docks and other structures, encrusting any solid surface.
Thousands can be found on a single square foot of space. Because of their huge numbers, the mussels clog intake valves and create numerous problems for hydroelectric power plants such as the one at Bagnell Dam.
Public awareness and education efforts continue to be the most effective means of preventing the spread of the nuisance species.
The lake had managed to avoid the infestation of zebra mussels . There had been several close calls where boats arrived and while waiting to be launched zebra mussels were found attached to hulls or intake valves. Those boats were caught before hitting the water by employees at marinas who knew what they were.
It wasn’t until 2006 that first mussels were found in the lake.
Since then the mussels have been found at various locations and have spread to the Osage River. Boats being trailered from infested waters to other locations are a common way for the species to be introduced to a waterway.
Preventing the spread
To prevent the spread of zebra mussels throughout Missouri and North America - and to keep your own equipment from being fouled - please observe the following “clean boating” suggestions when transporting your boat from waterway to waterway.
Inspect: Thoroughly inspect your boat’s hull, drive unit, trim plates, trolling plates, prop guards, transducers, centerboards, rollers, axles, anchor, anchor rope and trailer.
Scrape off and trash any suspected mussels, however small.
Remove all water weeds hanging from the boat or trailer before leaving any water body.
Drain: Drain water from the motor, livewell, bilge and transom wells and any other water from your boat and equipment while on land before leaving any water body.
Dump: Trash leftover bait on land, away from water, before leaving any water body. Leftover live aquatic bait that has contacted infested waters should not be taken to uninfested waters.
Rinse: When you get home - before launching your boat into uninfested waters - thoroughly rinse and dry the hull, drive unit, livewells (and livewell pumping system), bilge, trailer, bait buckets, engine cooling system and other boat parts that got wet while in infested waters; use a hard spray from a garden hose.
If the boat was in infested waters for a long period of time, or if there are any attached adult mussels, use hot (104 F) water or tow the boat through a do-it-yourself carwash and use the high pressure hot water to “de-mussel” the boat. Do not use chlorine bleach or other environmentally unsound washing solutions.
Dry: Boats, motors and trailers should be allowed to dry thoroughly in the sun for at least five days before boating again.
In the Slip: In infested waters, the best way to keep a hull mussel-free is to run the boat frequently (small juvenile mussels are quite soft and are scoured off the hull at high speeds).
