Biologist conducts electrofishing survey to index abundance of sea lamprey larvae (FWS photo)

In an attempt to further suppress the increasing number of parasitic sea lampreys in most of the Great Lakes (Lake Ontario is the exception) and reduce operational costs, the Sea Lamprey Management Program is implementing a new, research-tested approach to replace its relatively expensive quantitative assessment program for a less intensive, yet not significantly less accurate method using rapid assessment techniques to rank tributary streams for lampricide treatment. 

From 1994 through 2007, a labor-intensive, quantitative habitat-based larval assessment program was developed to accurately rank the production of metamorphosing larval sea lampreys and the cost to remove them from those streams.  The quantitative assessment technique was based on measuring year specific larval habitat, densities, and size structure in streams, and predicting the number of metamorphosing larvae from those streams if not removed with lampricide the following year.  At that time the quantitative program was developed, the underlying assumption was that further suppression of sea lamprey populations would be achieved through better choices of specific streams to treat by using more perfect knowledge. Unfortunately, over time the added cost of this program translated to fewer streams being treated and presumably additional parasites recruiting to the Lakes. 

From 2005 through 2007, the agents of the Great Lakes Fishery Commission (US Fish and Wildlife Service [Service] and Department of Fisheries and Oceans Canada [DFO]) tested an alternate stream treatment selection model that targets additional sea lampreys using a less expensive, albeit somewhat less accurate technique and use the savings to target additional streams for treatment. The research focused on the question of what an optimal control program should look like; with a finite amount of financial resources available for control, how many dollars should be spent on assessment, with the understanding that fewer dollars then become available for lampricide treatments.  Results of the comparative testing were so promising, that the Commission directed its agents to implement the new stream selection program during 2008, one year earlier than expected.  The new technique relies more heavily on historic measures of larval sea lamprey habitat in streams, uses expert judgment based on over 50 years of experience to help determine which streams to examine and when, and employs a rapid assessment technique to index the abundance of larger larvae in those streams.  As implemented during 2008, efforts to rank streams for treatment are reduced by about 60% and those redirected resources are being used to target and remove more sea lampreys by conducting additional lampricide treatments.

While only time will tell if parasitic sea lampreys will be further suppressed, the future looks brighter today for lake trout restoration.