Zebra mussel case study shows total erradication may be possible

The innocent looking zebra mussel.The case of zebra mussel eradication...
Scientists conducted a case study of an attempt to completely eradicate zebra mussels using SCUBA-based removal from Lake George, NY after the exotic species had been discovered. The researchers wanted to test the hypothesis that that early detection and rapid removal of a significant fraction of a population of zebra mussels is a feasible management approach for the eradication of the founding population and the prevention of new infestations.

A native to the Black, Caspian and Aral seas, Zebra mussels were first introduced to the Unites States in 1986 and have since colonized many of the freshwater systems of the Eastern United States and Canada. Zebra mussels have encountered very little competition from native species or mortality from predators or parasites, and thus, have found much success as an invasive species. As with many invasive species, the ongoing costs of controlling zebra mussels are high and therefore it's recommended that the invasion be detected as early as possible and the species be totally eradicated.

Case Study Findings...Zebra mussel-encrusted vector averaging current meter in Lake Michigan. Photo credit, M. McCormick.
In 1999, adult zebra mussels were found in Lake George. From late 1999 until June 2001 scuba divers concentrated on the areas of highest infestation and removed approximately 90% (19,176) of the mussels found on the site during the study period. The total time spent was 276 hours. From October 2000 to September 2007 divers spent an additional 584 hours conducting follow-up control and removing an additional 2076 mussels. Periodic inspections down current and at the margins of the invasion site have found no evidence of recruitment suggesting that there has been no further reproduction since the eradication efforts began.

Implications for Conservation...
The Lake George zebra mussel removal project is one of the first examples of successful eradication of the species post invasion without using chemical treatment. The researchers caution that we may not want to declare "Mission Accomplished" just yet and ongoing monitoring will be needed. This particular case may not be generalizable to all situations - particularly because Lake George has low calcium levels that may inhibit zebra mussels from establishing. The study authors state that control efforts would not have been possible if the project had to be fully funded. Instead, the eradication efforts relied largely on the work of SCUBA volunteers.

Nonetheless, this study should give managers hope that early detection and rapid deployment of SCUBA-based removal can be an effective eradication strategy.

Source:	Aquatic Conservation: Marine and Freshwater Ecosystems
Title:	Eradication of colonizing populations of zebra mussels (Dreissena polymorpha) by early detection and SCUBA removal: Lake George, NY
Authors:	a) John Wimbush, b) Marc Frischer, c) Joseph Zarzynski and a) Sandra Nierzwicki-Bauer
	a) Rensselaer Polytechnic Institute; b) Skidaway Institute of Oceanography c) Bateaux Below, Inc.