Imagine walking along the banks of Lake Champlain and stumbling across a herd of grazing zebra. Chances are you would be baffled by their presence, and likely a little concerned. You might wonder how and why these creatures, which ordinarily dwell in the Serengeti, have come to thrive along the shores of a lake in upstate New York. If you were wise you might also ponder the impact they might have on the local ecosystem, and question what could be done to slow their proliferation.
Although there isn’t much chance of seeing a zebra, specifically, the presence of less obvious nonnative species has become an increasingly serious issue for the Champlain waterway. According to the Lake Champlain Basin Program’s data nonnative species were first recorded within the lake as early as 1840 and today at least four dozen aquatic nuisance species can be found within the waters. Among these are the Zebra Mussel, a mollusk originally native to the Caspian and Black Sea regions of Eurasia, the Alewife, an oceanic fish which has established populations in landlocked lakes across New England, and the Rusty Crayfish, a breed native to Tennessee which frequently hybridizes with local crayfish populations. To add to this list, several species including Gizzard Shad and Blueback Herring have recently been introduced to the Great Lakes region, and the threat of infestation by such breeds as Round Goby, Eurasian Ruffe, and Guagga Mussels, to name a few, appears imminent.
Ironically, since the enactment of the Clean Water Act in 1977 many nuisance species which were previously incapable of proliferating due to pollution have begun to reproduce at disconcerting rates in the more hospitable waters. These exotic fish and plants have had profound effects on the bionetwork of the Lake Champlain Basin. Nonnative plants and animals compete with native species for food and resources, feed on native larvae and eggs, and crowd out and inhibit native plant growth. They have also been known, in the case of the Sea Lamprey, to prey on other fish. The Lake Champlain Sea Lamprey Control reveals a mortality rate of 40-60% of fish wounded by Sea Lamprey. The Lamprey has been known to attack Atlantic Salmon and Lake Trout. Not only has this been detrimental to the ecology in the area, it has also limited the development of the Lake Champlain fishery and has impacted recreational and economic opportunities on the lake.
There are several ways in which nuisance species have been introduced and spread throughout the Great Lakes and the majority of them have been through human interaction with the terrain. Some plants, such as Purple Loosestrife and Japanese Knotwood, have been planted in home gardens only to spread into the wild. Similarly, fish species such as the Tench have been used as live bait. The surviving fish then breed and form new populations in nonnative waters. Zebra Mussels, which have threatened at least seven mussel species native only to Lake Champlain, appear to have spread by the dumping of ballist water from ocean-going ships into the waterway. Recreational boating, diving, fishing etc. can also cause mollusks and algae such as Didymo to be inadvertently transported between bodies of water.
Attempts to stop or at the minimum control proliferation of exotics are both difficult and costly. According to the Lake Champlain Basin Program, over $4.1 million have been spent attempting to control the Eurasian Watermilfoil population in Lake Champlain since 1982. Thus far none of their attempts which have included hydro-raking, installation of bottom barriers and lake level drawdown have been overly successful. In the case of some species, such as the Rusty Crayfish, once a colony has been established there are no known methods of removing the invaders.
Dealing with the introduction of exotic species has been both a costly and difficult task that both grass-roots environmental groups and government agencies have struggled to undertake. Even the layman, however, can help prevent the introduction and spread of nonnative species. Boaters should take care to properly clean their boats before travelling from one body of water to another. Fisherman should never use nonnative live bait. Gardeners should take steps to ensure that they are not planting nonnative plants, as even supposedly “sterile” varieties frequently sold in garden shops have been known to proliferate. Taking these steps may not solve the problem, but it is the responsibility of each of us to do what we can to prevent the spread of non-native species.
Nicole Ballinger, Aquatic Nuisance Species in Lake Champlain & the Basin, www.lcbp.org/nuissum.htm
Lake Champlain Sea Lamprey Control, www.champlainlamprey.org
Amy Benson, US Department of the Interior/ US Geological Survey, http://fl.biology.usgs.gove/nonindiginous_species
Christine Mainene, Invasive Species in the Great Lakes Region, http://www.great-lakes.net/envt/flora-fauna/invasive/invasive.html