Cormorant culling is the intentional killing of cormorants by humans for the purposes of wildlife management. It has been practiced for centuries, with supporters of culling generally arising from the angling community. Culling techniques may involve the killing of birds, the destruction of eggs, or both. Historically, culls have occurred to protect the interests of recreational and commercial fishermen who perceive the animals to be competing with them for their intended catch or for the prey of their intended catch. Since the 1960s, the growing aquaculture industry has undertaken cormorant culls to protect its farmed fish and crustacean stocks. Opponents of cormorant culling include conservation groups such as the National Audubon Society, Cormorant Defenders International and Sea Shepherd.
Target species
The target species are primarily the double-crested cormorant in North America and the great cormorant in Europe, Japan, and Australia. The little black cormorant has also been targeted in Australia. In Africa, the reed cormorant is targeted and shot.
Double-crested cormorant
Before Europeans became a major presence, double-crested cormorants lived throughout much of their current North American range, usually in populations far greater than 21st century observations. After birdwatching near Natchez, Mississippi in December 1820, John James Audubon reported: “We saw to day probably Millions of those . . . Cormorants, flying Southwest—they flew in Single Lines for several Hours extremely high.” No comparable numbers of the birds can be seen today.
After a protracted period of cormorant population reduction due to expanding human settlement, breeding habitat loss, and persecution in the forms of shooting and egging, a turning point for the species was reached in 1972. The National Audubon Society listed the double-crested cormorant as a species of special concern. The state of Wisconsin declared cormorants endangered and began building nesting structures to help them return. The use of DDT, a chemical agent which was proven to thin cormorant eggs and had impacted recruitment since its introduction following World War II, was banned. Congress also signed a revised Migratory Bird Treaty Act granting cormorants federal protection. Since that time, the species has been recovering.
Catfish and baitfish aquaculture have grown rapidly since the 1960s, particularly in the south-eastern United States. Open aquaculture ponds provide winter or year-round homes and food for cormorants on the species' long-established migration route. This has also led to conflict and prompted culling at aquaculture facilities. Cormorants’ effect on the aquaculture industry is significant, with a dense flock capable of consuming a harvest. Cormorants are estimated to cost the catfish industry in Mississippi alone between $10 million and $25 million annually.
The double-crested cormorant is the only species appreciably found inland in the United States.
Methods
Shooting
Shooting is the most commonly employed and immediately effective method of cormorant culling. Sharpshooters are sometimes hired to undertake the work (Shiga prefecture, Japan) and in some jurisdictions, hunters are issued permits to allow them to kill these otherwise protected birds (South Carolina, United States). Birds can be shot on the water, on the wing, or at their breeding sites.
Egg smothering
The smothering of eggs with food-grade corn oil is another method employed by authorized persons. Once applied, the eggs' porous surface, which allows the transport of oxygen, becomes clogged with oil. The parent birds continue to incubate the oiled eggs, which ultimately fail to hatch.
Culling by region
Cormorant culling has occurred in many countries including Australia, the United Kingdom, Germany, Estonia, Japan, the United States and Canada.
Australia
The culling of cormorants occurred in Australia from the 1900s to the 1960s for the purposes of reducing competition with recreational and commercial fisheries. In some cases, bounties were offered as incentives to encourage people to hunt the birds. Primary target species included the little black cormorant and great cormorant.
New South Wales
In New South Wales, a bounty was in place for a number of years prior to 1919. It was discontinued as inland cormorant populations continued to be replenished via migration and it was proven to be ineffective in preventing fish losses. During the bounty period approximately 44,000 cormorants were killed.