Cisco, sometimes called lake herring, have neat ecological roles in the Great Lakes, according to the Michigan State University Extension. With decreases in alewife populations in the basin, scientists with the Extension say that cisco may soon be re-stocked in certain areas.
One reason that fisheries biologists want to re-introduce cisco in greater numbers is that they provide more nutritious food to trout and salmon up the food chain. Non-native alewife became the main source of food for those fish as alewife numbers grew, but they are not ideal for eating because of their elevated levels of thiamine that hurt the reproduction cycles of many Great Lakes fish.
In addition to cisco’s role as a prey fish, they are also a main predator of zooplankton, taking in the small creatures by filtering water. Unlike lake whitefish, which eat zooplankton near lake bottoms, ciscoes rest higher up in the water column to find their food.
Scientists with the Michigan State University Extension are in beginning stages of restoring other kinds of planktivorous fish to Lake Michigan. They have submitted information to the Great Lakes Fishery Commission arguing for the restoration of ciscoes to the lake.