Image: University of Minnesota

Ruffe--those fish you may only know as "orange" on a menu--have taken over one of the Great Lakes. It all started in the early 1980s when these Eurasian natives (right)--having hitched a ride across the Atlantic in ships' ballast tanks--turned up in the Duluth-Superior Harbor. Since then they have become the most abundant species trawled from that harbor's bottom. And although scientists don't yet know how the ruffe boom has affected native fauna, they would like to keep these immigrant fish away from the docks, where they might catch another ride elsewhere.

Peter Sorensen and his colleagues from the University of Minnesota Sea Grant program have recently discovered a possible solution. In the latest issue of the Journal of Great Lakes Research, they describe a potent pheromone that Eurasian ruffe emit when injured, and this chemical signal repulses other ruffe. "In large laboratory tanks, ruffe avoid the alarm pheromone upon contact," Sorensen says. "Clearly, this cue has the potential for managing ruffe. The key remaining question is how effective it will be in the large open spaces of the lake.