The U.S. Army Corps of Engineers and the U.S. Department of Agriculture’s Wildlife Services are preparing to cull thousands of double-crested cormorants in the Columbia River estuary, a move they say is necessary to protect baby salmon in the Pacific Northwest.
These cormorants are large, black birds whose webbed feet, long necks and hooked bills allow them to dive below the water’s surface in order to eat small fish. Scientists estimate the birds consume around 12 million baby salmon each year. Salmon travel from spawning grounds in the river to the ocean, and some of the species in the areas are federally protected.
Last week, hunters employed by Wildlife Services scouted a small island at the mouth of the Columbia River in Washington to prepare for the cull, which will reduce the population of the birds from around 14,000 breeding pairs to some 5,600 breeding pairs between now and 2018.
The plan for that reduction includes killing around 11,000 adult cormorants (approximately 30,000 currently live on the island), as well as spraying 15,000 eggs with vegetable oil in order to prevent them from hatching.
Workers have installed silt fencing, which will help to separate dense groups of cormorants, minimize impacts on non-target bird species and allow for more precise tracking of population figures.
Wild salmon are found in both the Pacific and Atlantic oceans, but populations have steeply declined in recent years and caused concerns in many regions. There have been some steps made in sustainable management of wild populations; Alaska’s fisheries management system, for example, is seen as a leader in managing wild fish stocks. Bristol Bay in Alaska sees about 38 million sockeye salmon return each year, a figure equivalent to nearly half of global salmon production. But management efforts in other regions often draw criticism.
Critics of the Columbia River plan say that nothing further should be done this year because the the feds are already starting two months later than recommended; that late start means that some baby chicks could starve to death after their parents are killed.
Conservation groups had also attempted to get a federal judge to block the plan, arguing that the birds kill far fewer salmon than the dams on the Columbia, but were unsuccessful.
Cormorants are only the latest species that have drawn attention for eating baby salmon in the region. Biologists have made multiple efforts to move Caspian terns away from the river with the same goal, and sea lions are also killed in order to prevent them from eating adult salmon going over the fish ladder of Bonneville Dam on the Columbia.