January 18, 1998                                                                   home page
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WAR DECLARED ON CORMORANTS   
A triple pincer movement threatens to roll back population gains made by double-crested cormorants since they were almost wiped out  in the early 1900's and suffered serious setbacks to their recovery from water pollution in the 60's and 70's.

Human fishers regard these aquatic, fish-eating birds as serious competitors for their finned prey.  Many human hunters look forward  to being granted a new species on which to test their marksmanship while at the same time performing a service for fishers.  Fish farmers, commercial fishers, charter boat captains and state game agencies that stock fish to enhance the success of those who buy fishing licenses all take a dim view of birds who gobble up their product.  The result is pressure to remove these prehistoric birds from their protected status under the Migratory Bird Treaty Act. 

There is no doubt that cormorants catch and eat a lot of fish, but it is
necessary to consider the number of fish they catch in relation to the number of fish taken by humans and other species.  According to the U.S. Fish & Wildlife Service (USFWS), worldwide studies have shown that cormorants consume "generally less than 5 percent of the quantity caught by commercial or sport anglers".  Most of the fish they catch  are "rough" fish as opposed to the species coveted by human fishers.  Analysis of stomach contents of cormorants in Arkansas found that  "sport-fish" constituted one percent of their diet.

A Lake Ontario survey placed the percentage of trout and salmonids consumed by cormorants even lower - at three tenths of 1 percent.   In response to concern that cormorant catches would deplete the food supply of "sport-fish", a survey in Western Lake Erie found that the number of fish caught by cormorants was "only about 1 percent of the prey-fish biomass needed to support populations of the walleye, a valuable 'sport-fish'."  Similar results were obtained in studies conducted on Lake Superior.

"Based on a review of the best scientific evidence, it does not appear that a strategy of reducing cormorant populations to benefit "sport-fish" populations is biologically warranted." the USFWS report concluded.

The National Audubon Society agrees.  In a letter dated January 12, 1998. Greg Clouser wrote on Audubon's behalf:  "There is absolutely no science to back their (sportfishing groups')  claims.

Cornell University conducted a study of the  cormorants on Oneida Lake, near Syracuse, where their populations had soared from none as recently as 1982 to 250 nesting pairs in 1997.  By mid or late September, there were an estimated 2,500 cormorants on the lake as the resident cormorants and their offspring were joined by migrating birds from farther north. 

Graduate students engaged in the study estimated that residents and migrants combined consume 40 metric tons of Oneida Lake fish a year.  This seems like a vast amount until you compare it with the 207 metric tons consumed by walleyes, a favorite catch of sport fishers.  Competition between the two species did not appear to be intense. The dietary staple of both species was yellow perch, but the walleyes consumed mostly fry and fingerlings while the cormorants preferred larger, year-old fish.  These preferences have the effect of giving the walleyes first crack at this preferred species in Oneida while the cormorants dine on their leftovers after they have grown to a larger size.

These modern studies confirm a 1915 an assessment by the Canadian Geological Survey that showed cormorants were not eating young salmon as feared by commercial and sport fishers, but rather "coarse fish" like sculpins, cunners, gunnels and eels, i.e. fish with little or no commercial value.

In spite of the lack of evidence that cormorants impact sportfishing unfavorably, and considerable evidence that they do not, Representatives John McHugh (R-NY) and Rep. Collin Peterson (D-MN)  announced their intention to introduce legislation establishing hunting seasons for double-crested cormorants  in order to reduce loss of fish stocks and interference with recreational and commercial fishing.

New York State Assemblyman Michael Bragman convened a cormorant management meeting  in Syracuse on October 16, 1997.  Participants "almost uniformly described the devastating ecological, economic, and social impacts of cormorant predation on Lake Ontario and Oneida Lake fisheries, local businesses, and surrounding communities."  Their testimony led Bragman to call for a cormorant management plan to be formulated before the 1998 spring migration.  He voiced the opinion  that New York's fishing-related tourism deserves as much consideration as southern fish farms, which can get permission to shoot cormorants. 

This is true, but only after non-lethal methods to discourage cormorants from preying on their fish have ceased to be effective.  They have permission to shoot only those cormorants actually preying upon or about to prey upon their fish.  Experience has shown that non-lethal methods such as noisemakers regain their effectiveness --for a time, at least-- after  birds have been killed or wounded there.

It is understandable that fishers, who have observed cormorants gobbling up a school of hatchery fish as soon as it has been released and even those who have watched cormorants dive and come up with a meal while their hooks remain barren,  feel that the cormorants are depriving them of success.  It  might help them to understand if they would read some of the reports of various studies instead of listening to each others tales of outrageous indignation.

Fish and wildlife officials have already developed ways of releasing fish to avoid cormorant predation.  One method is simply to release the young fish in areas removed from cormorant activity.  If this is not possible, as in a smaller lake, the fish can be released after dark when the cormorants are sleeping.  This works well for rainbows who have to be released in streams.  Another tactic is to make the releases before the cormorants return north in the spring. 

A more elaborate method being pursued by the Oswego Chamber of Commerce and charter boat captains is a "net pen" to keep the cormorants from getting at the young fish.  After the fish have had time to acclimate, the captains tow the pen out into the lake away from  cormorant-frequented areas and release the fish. 

Cormorant populations, which have begun to level out in the Great Lakes, are controlled to some extent by the number of nesting sites available to them.  Adults who are not successful in commandeering a site either don't breed or move elsewhere. 

These communal nesting sites have given fishers reason to complain eloquently about the odor caused by the elimination of digested fish, which does no harm when these sites are not close to human habitation as is usually the case.  Cormorants can be discouraged from nesting next door by clearing away their nesting material.

There is another side to cormorant excretions, however.  On islands off  the coast of Peru where 10 million cormorants congregate, their droppings are called guano and are harvested as what horticulturists consider to be the world's finest organic fertilizer.  The moister climate of the Great Lakes region does not permit the accumulations found in Peru, but the nitrates and phosphates that wash into the water can help counteract the effect of the zebra mussels by nourishing diatoms and algae that are the food base of all aquatic life.

It has been suggested that the larger cormorant population may interfere with other protected birds.  They may have displaced black-crowned night herons, in one instance.  Should this become a problem, their eggs can be addled by shaking them or dipping them in oil to pre

(cormorant slaughter continued from previous page 46)
vent them from hatching.  This method will limit local populations to existing adults which seems much more sensible than shooting cormorants everywhere to correct a problem on one small island, for instance.   Wildlife populations will generally sort such matters out for themselves, however, as they did for eons before modern humans started to interfere

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