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Cormorants: The Alewife, Alien Salmon and Trout, and the Double-Crested Cormorant

Published 01/25/11
By Barry Kent MacKay, Senior Program Associate

(Photo by Maha Rashi)

Two fish important to the double-crested cormorants in the Great Lakes are the alewife and the round goby.

Alewives are a shad-like fish that is native to the east coast, where it lives in seawater but moves into rivers to spawn in fresh water. No one can say with absolute certainty when or how the alewife reached the Great Lakes, but it was first recorded in Lake Ontario in 1837.

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Cormorants: The Round Goby

Published 01/25/11
By Barry Kent MacKay, Senior Program Associate

(Photo by Jeff Jones)

But if the cormorant’s taste for alewives is seen by wildlife managers as a negative, placing them in competition with alien salmon, there is another alien species to be considered: the round goby.

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Cormorants: The Difference Between Science and Management

Published 01/25/11
By Barry Kent MacKay, Senior Program Associate

Double-breasted cormorants
(Painting by Barry Kent MacKay)

Such terms as “science” and “scientist” are often broadly used to include practices that are not science and individuals who may or may not be scientists and may or may not practice science. For the purposes of better understanding cormorants or any other wildlife species it is important to distinguish between “science” and “management.”

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Cormorants: The Agricultural Subsidy

Published 01/25/11
By Barry Kent MacKay, Senior Program Associate

Double-breasted cormorant
(Painting by Barry Kent MacKay)

Whether we are talking about white-tailed deer, Canada geese, snow geese, double-crested cormorants, blackbirds, raccoons, crows, coyotes or any other native species of wildlife accused of being “too” common, one of the favorite reasons wildlife managers like to refer to, in order to explain why there has been an unprecedented increase in population size, is often called the “agricultural subsidy.”

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Cormorants: The Missing Predator Argument

Published 01/25/11
By Barry Kent MacKay, Senior Program Associate

(Photo by Jeff Jones)

Not that it should matter all that much whether cormorants have increased or, as the evidence indicates, decreased since earlier times. Virtually no species of North American bird exists at the same number as it did at some point when there was, presumably, the “right” number. Apart from those who are now extinct, all exist at greater or lesser numbers than at some pre-colonial point in time, their numbers reflecting the ever-changing ability of the environment to support them.

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Cormorants: Limiting Factors

Published 01/25/11
By Barry Kent MacKay, Senior Program Associate

Double-breasted cormorant
(Painting by Barry Kent MacKay)

Cormorants are dependent on accessible fish biomass, and there’s no doubt that it has increased in some places at the local level. A field that once grew cotton and now grows fish obviously provides more accessible food for cormorants, and as indicated above, it seems quite possible to think that while the Great Lakes — the largest body of fresh water on the continent — may have fewer fish overall than the vast numbers who met the first European colonists (indeed, several of those species that were once common now endangered or extinct), the arrival of alewives and round gobies may have enhanced the ability of the lower Great Lakes to feed cormorants over what existed centuries earlier.

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Cormorants: Semi-Science and Wildlife Management

Published 01/25/11
By Barry Kent MacKay, Senior Program Associate

(Photo by Jeff Jones)

Wildlife management responds to political direction that, in turn, responds to public demand. The public and the politicians they influence cannot be expected to know, or care, about the complexities inherent to the natural world. Everything must be simplified before it can be explained to the public. Fish are in decline, cormorants eat fish, ergo, cormorants are responsible for the decline in fish. This scenario is, generally, refuted by the scientific evidence, and cormorant detractors, be they the general public or wildlife managers, can act as though this evidence does not exist (although strides are being made, especially in Canada).

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Cormorants: So ... What Do Real Scientists Say?

Published 01/25/11
By Barry Kent MacKay, Senior Program Associate

Double-breasted cormorant
(Painting by Barry Kent MacKay)

For the past 200 years there have been numerous studies of double-crested and other species of cormorants, both in North American and abroad, a large number of them designed to examine the “impact” cormorants have on various fish species. In response to FEIS, the American Ornithologists Union (AOU) struck a panel of ornithologists, not exclusive of wildlife management interests but decidedly academic, to review the U.S. Fish and Wildlife Service’s management plan of 2003. They did a massive literature review and stated:

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