Ruffe: A Ballast Water Survey. Summary Report.

Abstract

Ruffe (Gymnocephalus cernuus), a non-indigenous species of North America, has been found at several locations in Lake Superior. This presents a serious problem, since the species has the potential to invade and subsequently disrupt valuable fisheries throughout the lake and eventually to migrate to the other Great Lakes, where additional problems might arise. Because of these concerns, measures are now being discussed as to how to contain the distribution of the species to a few locations. It seems highly likely that ruffe entered the lake in ballast water discharged from ships that had previously docked in Europe. This study was designed to examine the patterns of ballast water intake and discharge from shipping using the Duluth/Superior Harbor. The work was completed in 1996, since when, of course, there has been a substantial increase in the literature on the topic of exotic species � in the Great Lakes. All ships visiting the harbor in 1992 were surveyed and the owners were asked to provide information on ship movements and ballast water transportation. Over 1,000 ship visits were recorded during the shipping season. While the survey was supported by various shipping associations, the response to the questionnaire was not stellar, hence the details on ballast water usage, that are discussed in this report, must be treated with caution. The trends outlined here may be indicative of a general pattern, but until more work is done in this area, caveat emptor. Nevertheless, given the tremendous amount of inter- and intralake trade and the large quantities of ballast water moved from port to port, it seems inevitable that the ruffe will eventually spread to other sites throughout the Great Lakes.