Lake Mead National Recreation Area

Lake Mead National Recreation Area

Invasive Species: Zebra Mussels

August 29, 2008, 10:53 am

Mussels are a key part of our aquatic ecosystems. They’re filter feeders, meaning they filter the water as they eat the debris that floats in it. They also serve as a food source for birds, fish, small animals and even humans.

Usually there’s not much more to say about these mollusks, but one particular species, the Zebra--or Quagga--Mussel, has made a journey that highlights not only its hardiness, but also the vulnerable balance of native ecosystems. Zebra mussels are small, freshwater mollusk species named for the stripes that commonly line the outside of their shells. Their sizes and shapes range can vary – oblong to almost circular, measuring anywhere from the size of a fingernail to two inches long – so it can be tricky to identify at first.

The species is native to the lakes of Southern Russia but has been introduced, and has since caused quite a stir, in North America, the British Isles, Spain and Sweden. In these places the species has overgrown, and while it filters the water and provides food for bottom feeders in waterways, it’s more of an unchecked pest than anything. Zebra mussels are prolific. An adult female can produce between 30,000 and a million eggs in a year, which are fertilized during spring spawning sessions. What’s more, there are too few predators to keep the species in check.

Having so many mussels around may not seem like a big problem on its face, but it has proven to be quite costly not only to the other members of its ‘host’ ecosystem but to humans as well. Many native lakes in North American have seen their native mussel populations drop due to the invasion of the zebra. It tends to latch onto the hardest substrates in the watery environment. In silty sands, these objects are the native mussels themselves, which are then often killed by the attachment of the zebra. The U.S. coastguard estimates the cost of economic losses and control measures around the zebra to be worth about 5 billion dollars each year! These are hearty creatures that can survive out of water for several days or weeks if the temperature and humidity allow for it. Since 1988 they’ve have reproduced and weathered their way to richly populate all of the great lakes and begin a sprawl into the major rivers in the U.S.

Scientists predict that the zebra mussel will continue to spread its population range by riding along the bottoms of small vessels and tourist ships. Zebra mussels can disrupt the food chain in freshwater ecosystems, ruin facilities like docks and rams, clog pipelines and engines and litter beaches with their smelly shells.

But you can help to stop this trend of their growth in the U.S. Before launching your boat, you can check it thoroughly. Remove all mud, plant and animal debris from the boat, trailer and other equipment to enter the water. When you’re out of the water, drain the boat, motor and live well so that it can dry out – the boat needs to be completely dry for at least five days before entering another body of water. Doing your part will help protect freshwater ecosystems around the US and in our national parks, as well as reduce the dollars spent to reduce the damage caused by this prolific species.