Cormorant. Image: National Park Service
By Camryn Evans
Double-crested cormorants are continuing to draw attention from wildlife researchers amid strong disagreements about whether the birds – whose numbers have grown in recent decades – are harming fish populations, reducing recreational and commercial fishing opportunities and damaging natural habitats in the Great Lakes region.
Their consumption of threatened and endangered fish species is among the concerns.
These dark-colored water birds begin to consume upwards of 1 pound of fish daily as they age. And their hefty appetites are causing debate about what controls to allow and whether lethal methods are effective.
Ontario’s province-wide fall hunting season, launched in 2020, is one attempt to help control the population of these dark-colored water birds, but its effectiveness as a control method is being questioned.
Groups such as the Ontario Federation of Hunters and Anglers welcomed establishment of the annual hunting season.
The organization said it was “pleased to see that the government is finally recognizing the problems caused by overabundant cormorants and are taking action to control overabundant cormorant populations to help protect Ontario’s ecosystems.”
But experts from the U.S. Department of Agriculture, Michigan and Minnesota Departments of Natural Resources, New York Department of Environmental Conservation and Cornell University said allowing hunting across the province “is a poor method of addressing cormorant conflicts.”
Their recent article in the journal Avian Conservation and Ecology cautions against overgeneralizing the impact of cormorants on fish populations because what the birds feed on differs by available species, the age and size of the fish they eat, and where they feed in their respective territories.
While their increased abundance “is unquestionably a wildlife recovery success story,” the article said, cormorants’ voracious appetite does cause problems in some local fisheries.
Past studies “do not suggest cormorants are always or never an issue for fisheries, but their potential impacts vary by locations and conditions,” it said.
That fact raises challenges for natural resource managers and government and tribal officials who are trying to regulate fish and cormorant populations, according to the article.
Some of the heated disagreement centers on determining where hunting of cormorants benefits local fisheries versus where it is useless.
Cormorants disperse randomly, and hunting them in low-volume areas is ineffective in combating their possibly “deleterious” impacts, the article said
It said the U.S. Fish and Wildlife Service permit policy, which took effect in 2020, is intended to encourage “a suite of approaches” to cormorant control, starting with nonlethal activities such as site dispersal and removing nests before eggs are laid.
The birds are native predators and “natural components of the ecosystems they occupy,” it said, arguing in favor of “non-lethal measures and the least disruptive management” as principal considerations.
“Transferring responsibility for cormorant conflicts, either real or perceived, to the public through a hunting season not only will not work but is antithetical to basic principles of conservation and management of fish and wildlife.” it said.