Of some 30 species of cormorant in the world, two species predominate. The greater cormorant, Phalacrocorax carbo, which ranges from the northeast coast of the United States across Europe and into Africa and Southeast Asia, plagues European fisheries. Little Galloo is home to the double-crested cormorant, Phalacrocorax auritus, named for a pair of cowlicks that make a brief appearance on males at the start of the breeding season (see photograph, p.3).
The double-crested variety winters in the southern United States, where thousands of acres of accessible catfish farms may have contributed to the bird’s astronomical population growth. “It could be that the fish farms get the young cormorants through that crucial first winter, thus greatly increasing survival rates,” says ecologist Gerry Smith of Copenhagen, New York. In addition, the Migratory Bird Treaty Act of 1972 protects cormorants by making it a federal offense to shoot them, take their eggs or destroy their nests. Then, too, says cormorant expert Chip Weseloh of the Canadian Wildlife Service, “Bird populations do make eruptions and start to spread for no apparent reason. Overfishing disrupts whole ecosystems and may contribute to increases in cormorant numbers.” Weseloh means overfishing by humans, of course. But it’s humans who accuse the cormorant of overfishing.
By the late 1980s, LakeOntario fishermen were asking the DEC to do something about the bird’s role in declining fish populations. After studying the matter, the DEC in 1998 concluded that while cormorants do feed on yearling lake and brown trout, they don’t eat salmon or adult lake trout, which live in water too deep for them to reach. When fishermen complained that cormorants were eating too many alewives, depleting salmon and lake trout by depriving them of their major source of food, the DEC commissioned more studies. In 1999, the agency published a report asserting that the greater culprit in the decline of alewives was the zebra mussel, a modest-looking little bivalve from the Caspian Sea that infested the Great Lakes in the mid-1980s after stowing away in the ballast water of tankers and other merchant ships.
The zebra mussel’s meteoric rise makes the alewife empire look puny. Today, zebras cover much of the bottom of LakeOntario, in some places as thickly as 50,000 per square yard. Although no larger than a thimble, a single mussel can remove all the plankton from a quart of water every day. Together, the Clean Water Act and the zebra mussel have transformed the algae- and plankton-rich waters into a lake so clear that visibility now often exceeds 25 feet.
During the 1990s, Little Galloo’s cormorant population spiked to some 25,000 birds, then spread to neighboring islands. Fishermen watched helplessly as growing numbers of the birds dived into the water and emerged with fish. At the same time, smallmouth bass fishing wasn’t what it used to be. The local economy slowed. Soon, anticormorant senti ment, and tension, mounted. More yelling meetings took place. “Biological science, hell,” Clif Schneider, a retired DEC fisheries biologist snorted. “What you need here is a degree in political science.”