446 



Non-native Species — Our Living Re.sonrees 



Types of Observations 



Zebra mussels are observed and collect- 

 ed by artificial substrate samplers, plankton 

 nets, and inspection of pipes and water 

 intakes. In the Great Lakes pipes and water 

 intakes at power plants, water-treatment 

 facilities, and various industries pump lake 

 water into their plants. Zebra inussels clog 

 these water pipelines, causing serious 

 mechanical problems. The U.S. Coast Guard 

 found zebra mussels on navigational buoys 

 in the Great Lakes during routine inspec- 

 tions; these buoys now .serve as an artificial 

 substrate sampler, giving us hundreds of 

 records each winter. Zebra mussels have 

 also been collected inadvertently while sam- 

 pling for fish when using gill nets or when 

 collecting native mussels. The incidental 

 finds account for many important sightings 

 in newly expanded areas. 



Range Expansion 



Since the first zebra mussel was sighted 

 in 1988 (Fig. I), the species quickly colo- 

 nized regions in all five Great Lakes by 

 1990. Currently, they have been reported in 

 the waterways of 19 states and 2 Canadian 

 provinces (Fig. 2). They are established in 

 the Great Lakes and the following rivers: 

 Mississippi, Arkansas, Illinois, Ohio, 

 Tennessee, Cumberland. Hudson, 



Susquehanna, Ottawa, Niagara. Mohawk, 

 Genesee, Kanawha, and St. Lawrence. 

 Established colonies exist throughout the 

 lower Great Lakes (Erie, Ontario, and St. 

 Clair) wherever there is suitable habitat. 

 Lake Huron has populations in Saginaw Bay 

 and at the southern end of the lake where it 

 flows into the St. Clair River. There are also 

 a few isolated populations around the lake 

 and in the Georgian Bay area. Zebra mussels 

 are abundant in most of the southern portion 

 of Lake Michigan's shoreline froin 

 Sheboygan, Wisconsin, to Frankfort, 

 Michigan. The northern portion of the lake 

 has populations in Green Bay. Traverse Bay. 



1988 



• Sighting CZI Stales affected 



Fig, 1. States with zebra mussel sightings in 

 inland or adjacent waters. 1988. In 1989, they 

 spread to Lake Superior. Lake Michigan, and 

 Lake Ontario (National Biological Service, 

 unpublished data). 



89 



92 



93 



90 91 

 Year 

 Fig. 2. Numbers of states affected by zebra mus- 

 sels since their arrival in the United States in the 

 mid-1980's. 



and in the lake at Escanaba and St. Ignace, 

 Michigan. Zebra mussels have also been 

 found in 1 1 inland lakes in Michigan. Lake 

 Superior is the only Great Lake where zebra 

 mussels are not spreading quickly. Since the 

 first sightings in Duluth Harbor in October 

 1 989, they have been found only in Thunder 

 Bay (Canada), Sault Ste. Marie, and 

 Marquette, Michigan. 



The first sighting in the Mississippi 

 River was in Alton, Illinois, on 10 

 September 1991. Two days later a single 

 zebra mussel was found about 764 km (475 

 mi) upstream at La Crosse, Wisconsin. In 

 January 1992, mussels were found at 

 Clarksville, Missouri; Oquawka, Illinois; 

 and Genoa, Wisconsin. In July 1992, mus- 

 sels were reported near Winona, Minnesota. 

 By early 1993 (Fig. .3), almost every lock 

 and dam in the Upper Mississippi River 

 north of Dubuque, Iowa, had zebra mussels. 

 The Lower Mississippi River was colonized 

 more recently in the later part of 1992 and 

 early 1993. Mussels were collected in the 

 river at Greenville and Vicksburg, 

 Mississippi, in 1992. By the end of June 

 1993, zebra mussels were collected in 

 Louisiana at Shaw, Lettsworth, St. 

 Francisville, New Orleans, and Berwick. 



Vectors 



It is important to be aware of the spread 

 of nonindigenous species, especially ones 

 with the potential to be an ecological men- 

 ace such as the zebra mussel. The natural 

 means of dispersal is larval drift down- 

 stream. Aside from natural mechanisms, 

 canals and barge traffic in navigable rivers 

 are suspected as major vectors for dispersal. 

 In April 1992, a barge dry-docked for 

 repairs at Hartford. Illinois, had more than 

 1 ,000 zebra mussels attached to a section of 

 exposed hull (Keevin et al. 1992). The total 

 number of zebra mussels on the entire hull 

 could not be determined. The barge's log 

 book showed that it had traveled 20,558 km 

 (12,777 mi) up and down the Mississippi 



Fig. 3. States with zebra mussel sightings in 

 inland or adjacent waters in 1993. The range has 

 extended west of the Mississippi River into 

 Oklahoma by way of the Arkansas River 

 (National Biological Service, unpublished data). 



River from Minnesota to Louisiana in just 

 over I year before dry-docking. This docu- 

 mented long-distance transport of live mus- 

 sels gives credibility to the assumption that 

 barge traffic has been a primary dispersal 

 mechanism in navigable waters. Zebra mus- 

 sels can also be dispersed overland, espe- 

 cially by human activities such as recre- 

 ational boating. Dead zebra mussels from 

 Lake Erie were found on a boat trailer enter- 

 ing California (D. Peterson, California 

 Department of Water Resources, personal 

 communication). 



References 



Boydstun. C.P.. and A.J. Benson. 1992. 

 Nonindigenous report (1992:1): zebra mussel 

 (Dreisscna pitlymorpha) sightings in the 

 United States and Canada. National Fisheries 

 Research Center. Gainesville. PL. 10 pp. 



Griffiths. R.W. 1993. The changing environment 

 of Lake St. Clair. Proceedings of the Third 

 International Zebra Mussel Conference. 

 Toronto. Canada. 



Keevin. T., R. Yarbrough, and A. Miller. 1992. 

 Inadvertent transport of live zebra mussels on 

 barges: experiences in the St. Louis District, 

 Spring 1992. Zebra Mussel Research Tech. 

 Notes" ZMR-1-07. U.S. Army Corps of 

 Engineers Waterways Experiment Station, 

 Vicksburg. MS. 4 pp. 



Masteller, E.C.. and D.W. Schloesser. 1991. 

 Infestation and impact of zebra mussels on the 

 native unionid population at Presque Isle State 

 Park. Erie. Pennsylvania. Page 20 in 

 Proceedings of the Second Annual Zebra 

 Mussel Research Conference, Rochester, NY. 



For further information: 



Amy J. Benson 



National Biological Service 



Southeastern Biological Science Center 



7920 N'W 71st St. 



Gainesville, FL 32606 



