But such absurd scenarios (see Cormorants: Energy Transference, Basic Physics and the Technology Prosthesis) don’t happen in the wild, which is why both fish and cormorants continue to co-exist as they have for millions of years. To be sure, in North America one species of cormorant and several species of fish have been exterminated, but that is because humans, utilizing not their own metabolic energy but the energy derived from their technology, destroyed them.
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Unlike the cormorants in the swimming pool, or the fish, or any other species, humans are not dependent on their food for the energy they expand in procuring it; they use technology that derives its energy from other sources, particularly fossil fuels. Every species of cormorant and every native species of fish they eat have co-evolved through vast periods of time without extermination occurring.
Cormorants are superb swimmers, but they must push themselves through water that is clear enough for them to see through well enough to catch fish, and has enough fish of the right size and nutriment value to sustain them. They cannot stay underwater for much more than a minute, and most dives are of shorter duration. While larger fish provide more nourishment, captured fish must be small enough to swallow, and must be brought to the surface and positioned head-first to go down the gullet.
If the cormorant is a breeding female she must be able to catch enough fish to fuel her body’s increased metabolic needs to produce eggs, and later, enough to have fish left over to feed her babies, assisted by her mate.
She does not have our options. If the store we shop in runs out of the food we want, it will have other food, or we may go to another store, the food having been provided through technology. The cormorant is limited to food that is available within reach of her nest. If she has to fly too far to find fish, she reaches the point of diminishing returns, whereby the energy spent getting to where the fish are and obtaining food is greater than the amount of energy the food provides. Her nest must be in a safe place, where there is ample food within a relatively short distance. Cormorants cannot safely fish far from shore as they need to be able to sit in the sun and wind and dry their plumage. And it is preferable that the water is not too deep, as fish are then able to flee deep enough to be out of reach of the air-breathing cormorants. And while it is true that both parents incubate the eggs and feed and shelter the babies during their first weeks of life, it means that only one cormorant can be hunting fish at any one time.
Introduction: Why Cormorants Can’t Kill All Fish
Wildlife Management North and South of the Border
Energy Transference, Basic Physics and the Technology Prosthesis
NEXT » Cormorants: Food Chains and Basic Ecological Principles
The Alewife, Alien Salmon and Trout, and the Double-Crested Cormorant
The Difference Between Science and Management
Semi-Science and Wildlife Management