Exotic Species Threats to the Ohio River
An exotic species, by definition, is a non-native species originating from a different geographical area. Exotics can compete directly with native species, sometimes with negative impacts. Man is responsible for most exotic species introductions, intentional and unintentional.
Zebra mussels (Dreissena polymorpha) originated in Europe and were accidentally introduced into the Great Lakes Basin around 1986 through the discharge of ship ballast. Zebra mussels are now found in the Ohio River and continued expansion is expected, primarily due to the mussel’s ability to attach to watercraft.
Zebra mussels look like marine barnacles and have a yellowish or brownish shell marked with alternation wavy bands of brown or yellow. Adult zebra mussels can be as large as one and one half to two inches and live to five years of age. They have threadlike filaments used to attach themselves to boat hulls, navigational buoys, native mussels, and other submerged solid objects.
An adult zebra mussel can produce 30,000 – 40,000 eggs which hatch throughout the late spring and summer months. Larval zebra mussels are free-swimming creatures for a period of 8 – 10 days and do not require a fish host as our native mussels do. After 8 – 10 days the larvae that settle out on hard surfaces survive. All hard substrates and surfaces appear to be vulnerable.
As with other exotic species, zebra mussels are expected to greatly expand their range. In European fresh waters, where they have existed for many years, numbers peaked three to five years after introduction, and then eventually showed a 60 – 90 percent population decline.
Available research indicates the negative impact of zebra mussel colonization outweighs any positive impacts. Resource managers are most concerned with the fate of our abundant native mussel populations, since zebra mussels have been found attached directly to many Ohio River specimens. Zebra mussels frequently attach themselves to boat hulls, but they also infiltrate water cooling systems and intakes, engine compartments and bilges. Any part of a boat that comes in contact with water is capable of retaining zebra mussels. The mussels will not damage boat hulls, but heavy infestations will slow speed, impair handling ability, and reduce fuel economy.
If you normally boat in the Ohio River and plan to take your boat to an inland lake, the following precautions will help prevent the spread of the mussels and damage to your engine:
- Thoroughly clean the hull of the boat. If small zebra mussels are present, the hull should be scraped. An alternative is to leave the boat out of water for 10 days or more, as the mussels cannot live long without water.
- Because larval mussels can easily live for a month in areas where trapped water remains, all live wells, bilge areas, cooling systems, etc. should be disinfected with chlorine. Chlorine bleach added at the rate of one part bleach to 10 parts trapped water is recommended. Although most other fishing and boating equipment will not be infected unless left in the water where zebra mussels are present, items such as anchors and minnow buckets should also be disinfected with bleach.
- Approved antifouling materials should be applied to boat hulls to discourage zebra mussels from attaching. Although effective, tributyl tin compounds are not recommended because of water quality impact. Check with your boat dealer for the newest recommendations.
Because zebra mussels are present year-round, the entire boating season on the Ohio River presents a concern for watercraft users. The length of time a boat is in the water does not make a difference since zebra mussels can settle on boat hulls and enter boat intake systems within a matter of minutes. Learn more about aquatic invasive species in Ohio