U.S. Department of the Interior U.S. Geological Survey Zebra Mussels in the Eastern United States

Life History, Ecology, water) and other, suspended material. Zebra compared with that of many North Amer­ and Distribution off the mussels also produce a substance called ican rivers. Zebra Mussel pseudofeces, which consists of particles that are taken in through the inhalant siphon, Adult zebra mussels were found for the Dreissena polymorpha (Pallas), .cpm-r rejected as food, wrapped in mucus, and first time in North America in Lake St Clair monly referred to as the zebra mussel, or expelled. Pseudofeces commonly contain in June 1988. It is presumed that they were the traveling mussel, is a bivalve mollusc higher concentrations of metals and other unintentionally introduced as veligers in with a 2 to 5-year life span and a maxi­ contaminants, than do ambient sediment par­ ballast water from trans-Atlantic commer­ mum adult size of about 1 inch. Females ticles because of this process of aggregation. cial vessels originating from Black Sea begin to spawn by the end of their first ports in 1985 or 1986. The spread of the year of life, at a minimum water tempera­ Zebra mussel distribution is limited by zebra mussel in North America has been ture of 54°F. A single female can release water-quality conditions/In general, they rapid. As of January 1994, it has been iden­ at least 30,000 to 40,000 eggs per year. are found at a salinity of 0 to 4 parts per tified in the Great Lakes, as well as in the The eggs are fertilized in the water and. thousand, a pH of 7.4 to 9.0, a calcium con­ the Arkansas, the Cumberland, the Hudson, hatch into a; larval stage, called a veliger. centration of 20 to 125 milligrams per liter, the Illinois, the Kanawha, the upper and The veliger, with an initial diameter of a dissolved-oxygen concentration of 8 to 10 lower Mississippi, the Ohio, the St 0.002 to 0.003 in., is a temporary member mg/L, and a turbidity of 15 to 78 in. Secchi Lawrence, and Tennessee Rivers. The rapid of the plankton community,, but after 14 to disc depth. Optimum filtration and growth spread has been largely attributed to the 21 days, it develops a shell and seeks an occurs at 68°F and decreases rapidly at tem­ unintentional dispersal of adults attached to appropriate substrate on which to settle. peratures above 77°F. Settlement and the hulls of barges used for commercial nav­ attachment generally do not occur when igation in the inland waterways. It also is water velocities exceed 4.0 feet per second. likely that recreational boaters transported zebra mussels on their hulls to uninfested The zebra mussel is native to the Black, waters. In addition to being carried in a the Caspian, and the Azov Seas of south­ downstream direction by current, veligers ern and eastern Europe, indicating that it may have been transported randomly in bait is a temperate, cold-water-adapted spe­ buckets by recreational fishermen, cies. By the mid-1800's, it had spread to Great Britain, Germany, eastern Europe, A second, closely related species, Dreis­ 1/2 inch and western Russia. From there it spread sena bugensis(Andmso\), was discovered to Scandanavia and other western Euro­ in Lake Erie in 1992. Although similar in Once settled, zebra mussels attach to a appearance to the zebra mussel, the quagga surface by means of byssal threads. This pean countries. It generally is accepted mussel may have a different optimal tem­ "byssus" comprises an elastic protein that the zebra mussel has lower popula­ perature range, salinity tolerance, and habi­ coated by an adhesive secretion and is tion densities in European rivers because of the poor water quality of rivers when tat preference! produced by a gland in the foot. In the juvenile and early adult stages, zebra mussels can move over short distances by ZEBRA MUSSEL DISTRIBUTION IN THE UNITED STATES dissolving and reforming the byssus. January 1994

Once mature, zebra mussels tend to move less but are still motile. Individuals typically aggregate, and densities exceed­ ing 500,000 adults per square yard have been observed in water intakes within the Great Lakes. Although hard surfaces, such as rock and wood, are preferred, zebra mussels also will settle on soft sub­ strates, including sand and aquatic weeds.

EXPLANATION As a settled juvenile and later as an adult, Confirmed zebra mussel! sighting the zebra mussel uses its gills to filter water Modified from National Biological Survey through the mantle cavity, removing and . Galnesvllle, Florida consuming phytoplankton (algae in the New laws have been enacted in the attached. Large infestations of zebra mas- high-pressure hosing, and other means of United States and Canada in the wake of sels have .the potential to significantly physical removal of settled adults are use­ the zebra mussel invasion to prevent fur­ reduce the dissolved-oxygen concentra­ ful techniques. However, these options ther introductions of exotic species. Imple­ tions in rivers. This effect has been docu­ entail the transportation and disposal of mentation of these laws, which include the mented in the Illinois River under low- adult animals, which may be considered Nonindigenous Aquatic Nuisance Preven­ flow conditions in late summer. to be hazardous waste. tion and Control Act of 1990 (Public Law 101-646), should help avoid future envi­ By 2000, the potential economic disrup­ Exposure to hot water at 98°F for 1 hour ronmentally and economically costly intro­ tion to businesses, municipalities, and or 104°F for 15 minutes results in 100-per­ ductions of exotic aquatic species. public utilities, particularly those with cent mortality. Freezing can be an effec­ water intakes, has been estimated to tive method for removing zebra mussel Effects of the Zebra exceed $5 billion. Zebra mussels can pre­ infestations. At temperatures of less than Mussel Invasion vent proper closure of lock and dam struc­ 41°F, tissue-freezing time is less than 4.5 tures. When they attach to the hulls of hours. If surfaces can be dewatered during The invasion of North America by the boats, they increase drag and fuel con­ periods of subfreezing temperatures, then zebra mussel has created short- and long- sumption. Zebra mussels have the poten­ infestations can be eliminated. Electrically term effects on the aquatic environment, as tial to sink navigation buoys because they charged surfaces are effective in prevent­ well as on millions of water users. Unfor­ weigh 20 to 30 pounds per square yard. ing settlement of veligers. Several com­ tunately, these effects have been largely Large colonies attached to docks and piers mercially available sUicone-based paints negative, as is common with invading spe­ accelerate deterioration. On beach areas, with low to very low surface tension can cies. Eventually, we can expect that zebra colonies of zebra mussels can cut the feet be applied to prevent settlement or result mussels will reach equilibrium with other of bathers. Furthermore, the dead and in such weak attachment that zebra mus­ aquatic invertebrate species and become a decomposing animals create an aesthetic sels are detached by high current velocity permanent member of freshwater ecosys­ nuisance and a health hazard. or minimal surface abrasion. tems in North America: Control Options for Numerous oxidizing agents are effec­ Zebra mussels interfere with the nor­ the Zebra Mussel tive against zebra mussels, including mal food-chain interactions of filter feed­ chlorine, chlorine dioxide, ozone, potas­ ers in rivers by competing successfully Before malfunction of equipment or sium permanganate, and hydrogen perox­ for phytoplankton. Thus, larger zooplank- interruption of water flow, the need for ide. Typically, treated water must be ton, which are food for fish, have less to zebra mussel mitigation or control mea­ dechlorinated before it is discharged to eat and may be reduced in numbers. sures can be assessed by various types of the environment to protect native organ­ Zebra mussels will attach to native mus­ monitoring or inspections. Periodic exam­ isms from harm. Several other materials sels, many of which are already threat­ ination of artificial substrates or inspec­ can act as molluscicides, including copper ened or endangered, and can prevent.them tion of exposed or submersed surfaces can sulfate, zinc, and tributylin oxide. from opening or properly closing their reveal the presence of zebra mussel colo­ Research is underway to incorporate cop­ shells. Also, large infestations will reduce nies. Plankton sampling will indicate the per in various structural materials to be the food and dissolved-oxygen supplies to presence of veligers in the water and the used in areas of zebra mussel infestation. native mussels. Zebra mussels also attach potential for their settlement. All these substances may leach into the to crayfish and snails and can kill them. water and harm nontarget organisms. Settlement of adult zebra mussels on Various types of mechanical controls spawning grounds of sport fish may are available. Most commonly used No predators have been found in North reduce their reproductive success. screens have mesh sizes too large to pre­ America that feed exclusively on zebra vent entry of veligers. Separator filters or mussels. The freshwater drum (a fish) and The ability to extract suspended- automatic backwash filters can be used to some species of waterfowl feed on zebra sediment particles from the water column exclude some sizes of veligers. Buried mussels, but feeding will not be sufficient means that zebra mussels have the capac­ intakes or sand filters also can be used. to noticeably reduce the populations of ity to increase water clarity and, thereby, Replaceable screens can be used as a sub­ zebra mussels. Efforts are underway to algal growth. In addition, suspended-sedi­ strate for settlement of veligers and find strains of pathogenic bacteria that ment particles typically have organic exchanged for clean ones at appropriate could be used against the zebra mussel, compounds and metals adsorbed to their intervals. It may be possible to create and but this work is only in the initial stages. surfaces. As filter feeders, zebra mussels maintain current velocities exceeding 6.5 Kim H. Haag can bioaccumulate these materials in their ft/s, which will prevent settling of body tissues and pseudofeces. Concentra- veligers. A related strategy uses in-line, For additional information write to: ~ons of contaminants, including polyaro- high-speed agitators to kill veligers. District Chief, U.S. Geological Survey matic hydrocarbons and metals, and total Pulsed-shock (acoustic) waves have been 2301 Bradley Avenue organic carbon are found to increase in used experimentally to clean surfaces Louisville, Kentucky, 40217 soft sediments where zebra mussels are encrusted with zebra mussels. Scraping, (502) 582-5242

August, 1994 FS 94-014