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GLIN==> News Release - An "Alarming" Discovery for Ruffe

                               MN SEA GRANT
                               NEWS RELEASE
9/13/00                                                CONTACT: Marie Zhuikov
                                                       (218) 726-7677

                     An "Alarming" Discovery for Ruffe

Eurasian ruffe release a potent pheromone when they are injured that repels 
other ruffe and could be useful in controlling this exotic fish.  University of 
Minnesota Sea Grant researcher Peter Sorensen and his colleagues reported their 
findings in the latest issue of the "Journal of Great Lakes Research."  They 
found that damaged ruffe skin emits an odor, or alarm pheromone, repugnant to 
other ruffe that dramatically suppresses their swimming and feeding activities. 

"In large laboratory tanks, ruffe avoid the alarm pheromone upon contact," said 
Sorensen, professor of fisheries and wildlife at the University of Minnesota.  
"Clearly, this cue has potential for managing ruffe.  The key remaining question
is how effective it will be in the large open spaces of the lake," he said.  

Peter Maniak, Ryan Lossing, and Sorensen, all with the University of Minnesota, 
have been studying pheromones -- chemical signals that pass between organisms of
the same species and are detected by an animal's sense of smell.  Fish commonly 
use pheromones to coordinate activities, such as mating and schooling, in waters
that are often turbid, vast, and relatively featureless.  Alarm pheromones 
signal the presence of potential danger.  

"To the best of my knowledge, no one is actively managing ruffe right now," said
Sorensen.  "They have given up for lack of ideas or funding."  Since the alarm 
pheromone is non-toxic, specific, and easy to collect and apply, Sorensen hopes 
it will re-inspire efforts to manage ruffe.  

Authorities in Alpena, Michigan, have approached Sorensen about using the alarm 
pheromone to exclude ruffe from areas where they are not wanted, such as docks 
where ships take on ballast water.  Sorensen has also identified a ruffe sexual 
attractant that might be used in conjunction with the alarm pheromone.  

The perch-like Eurasian ruffe became part of the fauna in the Duluth-Superior 
harbor in the early 1980's.  Presumably, they crossed the Atlantic Ocean as 
accidental passengers in the ballast tanks of cargo ships.  Within a decade of 
their detection, Eurasian ruffe became the most abundant fish trawled from the 
bottom of the harbor.  Their impact on native aquatic species remains unclear 
but is under investigation.  Currently, ruffe have spread along Lake Superior's 
south shore to the Fire Steel River, east of Ontonagan, MI; to several harbors 
along the north shore to Thunder Bay, Ontario; and to Alpena, MI, on Lake Huron.

For a free copy of the journal reprint, "Injured Eurasian Ruffe, Gymnocephalus 
cernuus, Release an Alarm Pheromone that Could be Used to Control their 
Dispersal," contact Minnesota Sea Grant at (218) 726-6191 or seagr@d.umn.edu.  
Ask for item number JR 462.


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