CONTROLLING RANGE EXPANSION OF THE ROUND GOBY
(NEOGOBIUS MELANOSTOMUS) AND RUFFE (GYMNOCEPHALUS
CERNUUS) WITH PISCICIDES 

Mark L. Hanson, Verdel K. Dawson, Michael A. Boogaard, and Terry D. Bills
U. S. Geological Survey, Biological Resources Division, Upper Mississippi
Science Center, La Crosse, WI  54603.

The Great Lakes are becoming invaded by an ever increasing number of exotic
aquatic species, presumably as a result of ballast water releases from seagoing
freighters.   As these unwelcome organisms become more abundant and widely
distributed in the Great Lakes region, it is increasingly likely that some will
expand their range to suitable portions of other interior drainage basins.  Ruffe
(Gymnocephalus cernuus) are spreading eastward along the south shore of Lake
Superior and have been collected at Thunder Bay, Ontario and Alpena, Michigan. 
The Illinois Waterway System near Chicago provides a direct connection for the
continuous transfer of water from Lake Michigan to the Mississippi River and is
presumed responsible for the transmission of zebra mussels (Dreissena
polymorpha) to the Mississippi River drainage basin. The round goby (Neogobius
melanostomus) is an example of a recently introduced aquatic nuisance species
that is poised to follow the path of the zebra mussel from the Great Lakes to the
interior of North America.   Recent surveys suggest round goby are entering the
Illinois Waterway System from Lake Michigan via the Calumet River drainage. 
Concern for adverse impacts that could result from the introduction of additional
non-indigenous species to the Mississippi River and other interior drainages has
led to monitoring the spread of the organisms in this system and the suggested use
of chemical toxicants if the invasion continues.  However, little information is
available on the relative sensitivity of ruffe and round goby to piscicides.  Toxicity
tests of antimycin and rotenone (registered piscicides) and the lampricides
3-trifluoromethyl-4-nitrophenol (TFM) and Bayluscide were conducted with ruffe
collected from Duluth Harbor and round goby collected from the Illinois
Waterway in comparison with other fish species native to the Great Lakes. 
LC50's (lethal concentrations where mortality is expected among 50% of the
organisms), LC25's, LC99's, and 95% confidence intervals were determined.  The
tests evaluated the potential for selective removal of ruffe and round goby by
comparing their sensitivities to the piscicides with native fish species.  Newly
developed delayed-release formulations of Bayluscide and Antimycin were also
evaluated for controlling the normally bottom-dwelling organisms without
treating the entire water column.  These formulations would be useful for thinning
concentrated populations of the invaders to help reduce the tendency for range
expansion while causing minimal impact on native fish.

Keywords:  round goby, ruffe, non-indigenous, piscicides, control


Mark L. Hanson
Upper Mississippi Science Center
P.O. Box 818
La Crosse, WI 54602
Phone:  608-783-6451
FAX:  608-783-6066
MARK_HANSON@USGS.GOV