But as cormorant numbers increased, so, again, did their persecution. Invasive species, most notably alewife, round goby, and white perch, contributed over 80% and 90% of the diet of cormorants by biomass and number, respectively. Barry Kent MacKay January 2013. No salmonine species were detected suggesting that negative effects on this important fishery would likely occur only via direct competition for prey (e.g., alewife). Their historic comeback in Ontario has led many to believe the cormorants are an invasive … As well, cormorants are the only major predator of several damaging invasive fish species. Round gobies swim in an exhibit of invasive species threatening the Great Lakes ecosystem at Chicago's Shedd Aquarium. Cormorants are a native Ontario water bird who have not yet recovered to historic population levels. The return of cormorants is a good news environmental story that indicates reduced pesticide levels. In Michigan, cormorant control focuses on fish populations, as well as vegetation. A 2015 study of double-crested cormorant feeding in the southern basin of Lake Michigan at East Chicago, Ind., showed regurgitated pellets from the cormorant … 4. While it is true that the ammonia-rich droppings of cormorants kill trees and other vegetation, concerns about property damage are an invalid justification for the hunt. Cormorants were almost wiped out by the insecticide DDT in the 1950s and ’60s. Why People Kill Cormorants An Animal Rights Article from All-Creatures.org FROM. invasive fish and found that round gobies were 33 percent of that diet in 2008, said Nancy Seefelt, Central Michigan University assistant professor of biology. The white mulberry is a classic example of an invasive species in that it is a non-native species that has escaped “captivity” and established a breeding population that has expanded in … "Cormorants are very opportunistic," Seefelt said. Cormorant populations made a brief recovery during the first half of the twentieth century as people moved off islands to seek better opportunities and built new seabird habitat—in the form of reservoirs, dock pilings, and bridges. A study on the Niagara River showed that up to 85 percent of the cormorants’ diet during the breeding season consisted of the invasive, non-native round goby.