The Eurasian ruffe, a fish species inadvertently introduced into North America' s Great Lakes in recent years, feeds on the eggs of lake whitefish, a native species, thus threatening the lakes' natural ecosystem  To help track the ruffe' s spread, government agencies have produced wallet-sized cards about the ruffe
The cards contain pictures of the ruffe and explain the danger they pose; the cards also request anglers to report any ruffe they catch
Most people who fish recreationally on the Great Lakes are interested in the preservation of the lake whitefish because it is a highly prized game fish.