Our Liviiii; Rcsaunes — Invertchnitcs 



179 



species in the latter group occur in larger rivers 

 and reservoirs and are projected to suffer severe 

 declines as the zebra mussel in\ades these 

 ecosystems. 



The rapid decline of mussels during this cen- 

 tury went almost unnoticed until the past 30 

 years. Although most of the described threats to 

 survival of mussels have existed for more than a 

 century, the increased geographic area covered 

 by these threats and the cumulative effects of 

 human expansion and development have now 

 overwhelmed aquatic systems. 



The demise in both populations and species 

 diversity of our mussel fauna is likely occurring 

 in other freshwater mollusks (especially snails) 

 and aquatic organisms, but too few surveys have 

 been conducted to record such trends. 

 Conservation and restoration should focus on 

 the ecosystem and watershed level instead of 

 directing concerns to the individual species. To 

 effectively caixy out such a broad recovery 

 effort will require an unparalleled level of coop- 

 eration and coordination of private, state, and 

 federal agencies. Perhaps even more critical to 

 the success of ecosystem and watershed conser- 

 vation is the involvement of the general public, 

 conservation organizations, and private corpo- 

 rations. If the decline of aquatic mollusks con- 

 tinues, we will witness the greatest extinction of 

 these organisms experienced in modern times. 



References 



Baker. P.M. 1993, Resource management: a shell exporter's 

 perspective. Pages 69-71 in K.S. Cummings. A.C. 

 Buchanan, and L.M. Koch. eds. Conservation and 

 Management of Freshwater Mussels. Proceedings of a 

 symposium. Illinois Natural History Sur\ey. Champaign. 



Belanger. TV.. C.G. Annis, and D.D, VanEpps. 1990. Growth 

 rates of the Asiatic clam, Ci>il)iciilii fliimincii. in the upper 

 and middle St. Johns River. Florida. Nautilus 104:4-9. 



Ellis. MM. 19.^1. Some factors affecting the replacement of 

 the commercial fresh-water mussels. Ll.S. Bureau of 

 Fisheries Fishery Circular 7:1-10. 



Fuller, S.L.H. 1974. Clams and mussels (Mollusca: 

 Bivalvia). Pages 215-273 in C.W. Hart and S.L.H. Fuller, 

 eds. Pollution ecology of freshwater invertebrates. 

 Academic Press, New York. 



Layzer, J.B., M.E. Gordon, and R.M. Anderson. 1993. 

 Mussels: the forgotten fauna of regulated rivers. A case 

 study of the Caney Fork River. Regulated Rivers: 

 Research and Management 8:63-7 1 . 



Left. L.G.. J.L. Burch. and J.V. McArthur. 1990. Spatial dis- 

 tribution, seston removal, and potential competitive inter- 

 actions of the bivalves Corhunla fhiminca and Elliplii) 

 complanata. in a coastal plain stream. Freshwater Biology 

 24:409-416. 



Master. L. 1990. The imperiled status of North American 

 aquatic animals. Biodiversity Network News 3:1-2. 7-8. 



McMahon, R.F. 1983. Ecology of an invasive pest bivalve. 

 Corlncida. Pages SOS-SeT in W.D. Russell-Hunter, ed. 

 The Mollusca. Vol. 6. Ecology. Academic Press. New 

 York, 



Nalepa, TF., and D.W. Schloesser, eds. 1992. Zebra mussels: 

 biology, impacts, and control. Lewis Publishers. Boca 

 Raton. FL. 



Turgeon, D.D., A.E. Bogan. E.V. Coan, W.K. Emerson, W.G. 

 Lyons, W.L. Pratt. C.F.E, Roper. A. Scheltema, RG. 

 Thompson, and J.D. Williams. 1988. Common and .scien- 

 tific names of aquatic invertebrates from the United States 

 and Canada: Mollusks. American Fisheries Society 

 Special Publ. 16. 277 pp. 



Williams. J.D., S.L.H. Fuller, and R. Grace. 1992. Effects of 

 impoundment on freshwater mussels (Mollusca: Bivalvia: 

 Unionidae) in the main channel of the Black Warrior and 

 Tombigbee rivers in western Alabama, Bull, Alabama 

 Museum of Natural History 13:1-10. 



Williams J.D., M.L. Warren, Jr., K.S. Cummings. J.L, Harris, 

 and R.J. Neves. 1993. Conservation status of freshwater 

 mussels of the United States and Canada. Fisheries 

 18(9):6-22. 



Fig. 2. The percentage of the U.S. 

 mussel fauna classified by conser- 

 vation status category: undeter- 

 mined, endangered and presumed 

 e.xtinct, endangered, threatened, 

 special concern, and stable. 



For further information: 



James D. Williams 



National Biological Service 



Southeastern Biological Science 



Center 



7920 N.W. 71st St. 



Gainesville. FL 326,S3 



An early indicator of adverse human effects 

 on large open-water systems in North 

 America was western Lake Erie, part of the 

 Lake Huron-Lake Erie corridor of the 

 Laurentian Great Lakes (Fig. 1). Local pollution 

 of tributaries of western Lake Erie was recog- 

 nized as early as 1890. when populations of 

 whitefish (Salmonidaej and lake herring 

 {Coregonus artedi) in the Detroit River declined 

 (Beeton 1961). Waters of western Lake Erie 

 stopped yielding whitefish and hening in the 

 1920"s-30"s. bu"t not until the 1950's. after 

 extensive biological investigations, were the 

 open waters of western Lake Erie believed to 

 have been polluted by human "local" activities 

 (National Academy of Sciences 1970). 

 Eutrophication (the addition of nutrients) of 

 western Lake Eiie created unsuitable conditions 

 (primarily low dissolved oxygen concentra- 

 tions) for fish and other animals in a major por- 

 tion of Lake Erie — the world's 12th largest lake. 

 By the early 1960's, Lake Erie was declared 

 "biologically dead" (Bums 1985), 



Among the many ecosystem components 

 affected by human-induced changes to western 

 Lake Erie (Burns 1983) is the native mussel 

 fauna (Bivalvia: Unionidae). Reduced mussel 

 populations that survived degraded conditions of 

 the I950's have been used in status and trends 

 studies to evaluate traditional forms of pollution 

 in western Lake Erie. Studies in the I990"s have 

 focused on evaluating the effects of exotic 

 species on mussel populations in the Lake 

 Huron-Lake Erie corridor. Exotic species have 

 recently been characterized as "biological pollu- 

 tion," a new concept in evaluating status and 

 trends data. Our study shows both historical, 

 long-term effects from human activities and 

 recent, dramatic effects from exotic species on 

 mussel populations in waters of the Great Lakes. 



Sampling Populations 



The Lake Huron-Lake Erie coiridor receives 

 water from three of the five Laurentian Great 

 Lakes, the largest freshwater system in the world 



Freshwater 

 Mussels in the 

 Lake Huron- 

 Lake Erie 

 Corridor 



by 



Don W. Schloesser 



National Biological Service 



Thomas F. Nalepa 



National Oceanic and 



Atmospheric Administration 



