Zebra mussel numbers declining in Lake of the Ozarks

MDC attributes decline to warm water temperatures, but cautions that it is still necessary to be extra vigilant to prevent the spread of the invasive species

The number of zebra mussels in Lake of the Ozarks has declined overall and disappeared completely in some areas.

The number of zebra mussels in Lake of the Ozarks has declined overall and disappeared completely in some areas.

According to the Missouri Department of Conservation (MDC) over the past several years, the number of zebra mussels in Lake of the Ozarks has declined overall and disappeared completely in some areas.

Zebra mussels were introduced into the Lake in 2006. For several years following their introduction, the invasive mussels spread rapidly. Populations became established in the Osage River below Bagnell Dam and in the Lake, itself, from the dam to the Gravois Arm. However, for the last couple of years, zebra mussels have declined or disappeared altogether from some areas of the Lake and MDC Fisheries Biologist Greg Stoner says the warm water temperatures during the summer is probably a factor in the invasive species decline.

The summer of 2011 was hot and this year is much worse with Lake water temperatures reaching hovering around 90 degrees. Those high water temperatures are enough to stress or kill the mussels that are native to the much cooler waters of the Caspian Sea. Disease and natural predators may be other factors that have contributed to the decline, Stoner said.

Despite the recent decline however, the MDC says public awareness and preventing the spread of the mussels on boats and other marine equipment are the best are still the best way to stop, or at least slow down, the spread of the invasive species.

In the case of zebra mussels, once they start multiplying they clog water intakes, disrupt aquatic life and cause untold damage to boats, docks and other native species. The good thing is that the public can avoid carrying the mussels from one waterway to the next by simply cleaning boats, fishing tackle and other water-related gear before moving it from one waterway to another.

The invasive zebra mussel, native to the Caspian Sea region of Asia, was accidentally brought to North America in the ballast water of an international ship in 1986. Since then, the mussels have rapidly reproduced and infested waters throughout the Great Lakes and the Mississippi, Arkansas, Ohio, Tennessee and Cumberland rivers and several of Missouri’s largest lakes.

It’s easy to forget they’re lurking about, but ditching the hitchhikers before launching a boat or introducing other marine equipment into the Lake is something everyone can do to help keep Missouri’s native aquatic species healthy. So whether you live at the Lake year-round, are a second homeowner or just visiting remember to check your boating and fishing gear and heed the following tips from the MDC for keeping the invasive species at a minimum.

Zebra mussel prevention tips

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.


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 water from the motor, livewell, bilge and transom wells and any other water from your boat and equipment while on land before leaving any body of water.


Trash leftover bait in a land-based container, never dump bait in the water. Do not transport live bait from one waterway to another, especially if the bait container has been submersed into the first waterway.


When you get home thoroughly rinse and dry the hull, drive unit, livewells (and livewell pumping system), bilge, trailer, bait buckets, engine cooling system and of your boat. Use a hard spray from a garden hose to rinse the boat completely.

If your boat was in infested waters for a long period of time, or if you find any attached adult mussels, use hot -104 F - water instead of cold for rinsing purposes, or take the boat to a carwash and use the high-pressure hot water to clean it.


Boats, motors and trailers that may have become 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).

On boats that remain in the water, zebra mussels can attach to drive units, cover or enter water intakes, and clog, overheat and eventually destroy a marine engine.

If possible, leave outboards or outdrives in the up position. Periodically inspect hulls and drive units, and scrape free of mussels. Pump hot water through the engine's intake on a regular basis to prevent mussel growth inside the cooling system.

Identify the Enemy

Learn what these zebra mussels look like (at least those you can see). If you suspect you have discovered a new infestation report it the nearest MDC field office.


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