February 17, 2005
Zebra mussels confirmed in Grand Lake
Vinita — It is official, zebra mussels—the freshwater mollusks which have wreaked havoc on municipal water systems, docks and other solid structures in waters all across the country–have been found in Grand Lake. In early February, officials with the Oklahoma Department of Wildlife Conservation (ODWC) confirmed the presence of zebra mussels at the Disney State Park boat ramp.
“We inspected the boat ramp where the zebra mussel report came from,” said Cliff Sager, ODWC’s Northeast Oklahoma Fisheries Biologist. “We found three mussels attached to the substrate, confirming their presence in Grand. We also inspected the Cherokee State Park ramp and found no mussels. The numbers appear to be low in the areas we inspected, but it is safe to say that they are established in the lake.”
Unfortunately, no successful methods for eradicating the mussels has ever been developed. And their history in other bodies of water has proven that containing them can be a steep uphill battle. In fact, the United States Fish and Wildlife Service has dubbed the small mussels with the “D” shaped shell and dark and light stripes (hence the name) “public enemy number one” on the aquatic nuisance species list.
The history—and the problem—of the mussel’s North America “invasion” has been well documented. They traveled across the Atlantic Ocean attached to the hulls of ships coming from Eastern Europe. In the late 1980s they were discovered in the Great Lakes and since then, they have spread down the Mississippi River, causing expensive problems wherever they go. Industries and municipalities along mussel-infested waterways in the Great Lakes region spend millions annually trying to contain them.
The Zebra Mussel Problem
What makes a small, seemingly harmless mollusk such a nuisance? According to Dr. Darrell Townsend, Ph.D., superintendent of GRDA Ecosystems Management, there are plenty of reasons.
"When you introduce an invasive, non-indigenous species like a zebra mussel into a new environment, it can cause a lot of problems," said Dr. Townsend. "Given the fact that they can reproduce very rapidly, they not only impose a serious threat to biodiversity, but they can have serious management implications for recreation and power generation alike."
In fact, “it’s possible for them to reproduce one million offspring in a season,” said Everett Laney, fisheries biologist with the United States Army Corps of Engineers. In the late 1990s and again in the summer of 2003, Laney was the key presenter at a series of public meetings held to inform Grand Lake area residents about the zebra mussel threat. He is also chairman of the Oklahoma Zebra Mussel Task Force. That group, established in the early 1990s, has tracked the Oklahoma mussel invasion which now includes the McCllelan-Kerr Navigation System, Oologah Lake (summer 2003) and, today, Grand Lake. “And once they arrive, they are there to stay,” said Laney, during his seminars. “You really can’t eradicate them. You just try to control them.”
Yet even as biologists look for methods to control them, the zebra mussels continue to be full of surprise. Originally, the mussels were thought to be a cold water species. Researchers believed they would spawn a couple of times a season, but when the water got over 80 degrees, they would get stressed and only be able to survive a few days. In fact, it was believed spraying heated water onto the mussels would be an effective method for eradication. However, since their arrival in Oklahoma, the mussels have adapted. Researchers now know they will spawn in warm water, even surviving in water over 90 degrees for several weeks. Also, it was once believed the mussels grew at a rate of one centimeter per year, and thus, their size was a good way to determine their age. However, later research has shown they can grew by one centimeter per month in the nutrient-rich waters of Oklahoma.
The mussels thrive in nutrient-rich waters because they are filter feeders, and each adult mussel can filter a liter of water per day. As they do this, they remove almost every microscopic aquatic plant (phytoplankton or algae) and animal (zooplankton), leaving behind clear, but nutrient-poor water, causing problems for other species.
“As they filter the water, they disrupt the food chain by redirecting energy flow," said Dr. Townsend. "They can compete for food with some freshwater fish species, potentially disrupting growth and survival of many game species."
Recognizing the threat
Although the mussels have been confirmed to be in Grand Lake, there are still steps that can be taken to help hinder there spread across the water “and it’s in the best interest of all Grand Lake residents and visitors to follow these steps,” said Dr. Townsend. “Hundreds of boats are going in and out of Grand Lake all the time, so cooperation is an essential part of our efforts to try to keep this infestation in check.”
Adult mussels may attach to hard surfaces, and the young larval form of the zebra mussel, called veligers, may be transported in water. Veligers are transparent and small — about the size of the period at the end of this sentence — and may be able to survive in any residual water. This is why preventing the transport of water in the bilge or live-well of boats is critical to stopping the spread of zebra mussels. Boaters who frequent known zebra mussel waters should be especially cautious. The mussels attach themselves to, and grow within, water intakes of both inboard and outboard motors and the subsequent restriction of water flow can cause motors to overheat.
Meanwhile, GRDA is working in close cooperation with Dave Neel, United States Coast Guard Auxiliary Flotilla Commander, to erect zebra mussel warning signs at many public boat ramps to increase awareness and to help prevent further spread of this noxious invader.
Here are some steps you should keep in mind to help hinder the mussels spread:
• Boats should not be left in the water for extended periods of time. With regular use, engine heat should keep mussels from colonizing inside most engine parts.
• Always drain the bilge water, live wells and bait buckets.
• Inspect the boat and trailer immediately upon leaving the water.
• Scrape off any mussel found. DO NOT return them to the water.
• If possible, dry the boat and trailer for at least a week before entering another waterway. (If conditions are right, mussels can live for up to seven days on a boat hull outside the water.)
• Wash boat parts and accessories that contact the water using hot water (at least 140 degrees Fahrenheit), a ten percent solution of household chlorine bleach, or hot saltwater solution. Do not wash the boat at the ramp where these solutions could pollute the water. Always finish with a clean water rinse.
For more information on zebra mussels, or to report a possible sighting, contact the GRDA Office of Ecosystems Management at (918) 782-3382, or visit the GRDA Office of Ecosystems Management page on www.grda.com.
