When the American Boat and Yacht Council organized the inaugural Aquatic Invasive Species Summit, it opened a much-needed dialogue on the serious negative impact that invasive species will have on recreational boating and, therefore, the importance of the industry’s engagement.
Many have heard of invasive species, but few really understand their threat. While there are many different species, zebra and quagga mussels are the most recognized. They showed up in the Great Lakes in 1988 and within seven years had spread to connected waterways in 18 states and two Canadian provinces. Since then, they have spread overland to countless isolated inland waters.
Although there are many potential carriers that could account for the overland spread — waterfowl, for example — transient recreational boats are suspected of being the primary means of such dispersal. Mechanisms associated with boats — trailers, live wells, bilges, hollow lifting strakes, motor wells to name a few — have been identified as capable of transporting mussels.
So what do we know about zebras and quaggas? An adult female zebra mussel can produce 30,000 to 40,000 eggs in each reproductive cycle and she's very prolific, reportedly turning out about 1 million each year. She begins to reproduce within just six to seven weeks of settling.
The offspring start as a free-swimming microscopic larvae or plankton, correctly called veligers. The veligers will drift in the water for several weeks, but eventually settle onto any hard surface they find. And, because the larvae is microscopic, it can be carried in water contained in anything.
Zebra mussels are filter feeders, sucking the plankton out of about one quart of water per day. They open their shells to dump decomposing waste that ends up on the lake floor. Zebras hook onto and clog power plant intakes, attach to docks, pilings, boat engine intakes and hulls that don't have antifouling, for example. They even attach to aquatic plants. At the end of their four- to five-year life cycle, their very sharp shells can foul beaches.
It's notable that the 10 trillion zebras and quaggas blanketing the bottom of the Great Lakes and filtering out the plankton have succeeded in actually doubling water clarity during the last decade. Clear water sounds good, doesn't it? However, the lack of plankton floating in the water means much less food for native fish and clams. Zebras actually devastate native species by stripping the food web of plankton, which has a cascading effect throughout the ecosystem. Lack of food has already caused populations of alewives, salmon, whitefish, native clam species among others to plummet or disappear.
Another result is that the clearer water allows sunlight to penetrate to the lake bottom. This creates an ideal condition for algae to grow, which contributes to the spread of deadly algae blooms. The algae fouls beaches and causes botulism outbreaks that have already killed countless fish and more than 70,000 aquatic birds in the last 10 years, according to the U.S. Fish & Wildlife Service.
Zebra mussels also can tolerate a wide range of environmental conditions and adults can even survive out of water for about seven days. But it’s the microscopic veligers that can't be seen in water that are the real culprits. Even more unfortunate, the vast majority of the organisms that are natural enemies in Europe are not present in North America.
Once zebra and quagga mussels become established, they are impossible to fully eradicate. So far, scientists haven't found anything that will kill them all without also harming other wildlife. So a common prediction by scientists is that zebra mussels will continue spreading passively by ship and by pleasure craft to more waterways. And trailered boat traffic is the most likely vehicle for invasion into new areas. That's why it’s believed that there are already zebras from Massachusetts to Southern California.
Water resource managers that attended the ABYC summit are hoping the marine industry can design ways to help stop the spread. It's believed the spread is preventable if boaters thoroughly decontaminate, clean, dry and have no standing water in their boats and associated equipment before transporting them to new bodies of water. How to get that done without creating a scenario in which boating becomes such a hassle that people simply choose to get out of it, or never get in it, is the challenge for all concerned.
The ABYC's summit, then, was a major step forward in bringing together a large partnership of resource managers, industry people and the boating public to explore new ways to deal with invasive species. And the process, while just beginning, is off to a good start.