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manonthemoon,
You wrote that:
"An adult Cormorant can eat up to thirty Lbs. of fish a day".
While I am not about to get into eco systems or food chain discussions, I do want to point out that the largest of these birds grows to 5-1/2 pounds. Eating 30#s, as you suggest, seems a bit of a stretch. But then again, what would anyone expect of a fisherman.
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Heres a pic of them
http://img.photobucket.com/albums/v2...orantbirdb.jpg
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The way to a flyfisherman's heart is through his fly
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Cormorants are such spectacular birds to watch feeding on fish. They dive from 20 feet above the surface, seem to fly underwater for the longest time. Because of this they are blamed for devasting fish populations. I have heard many stories, or should I say "urban legends" regarding they ability to swallow a5 lb. fish or eat 30 lb. a day. Not true! An adult cormorant eats about one pound of fish per day. I have seen large groups of cormorants feeding on stocker trout in a small lake near the ocean and eating several each in a day. That's because these stockers are easy prey. They are hated by the fisherman that fish this little lake.
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Joe
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There are a lot of cormorants on Lake Champlain, and a lot of opinions about them. I doubt they have much true impact on the fishing. They go after mostly small perch and the perch here could stand some thinning out.
The real problems with them are the rookeries, where they kill trees with excrement and by tearing off branches for nests. Several Islands here have been "ruined" by them. I say "ruined" only from the standpoint of resale value, though. It's a NIMBY kind of thing. We have used a propane cannon to scare them off during nesting season with good success. Of course, they just go somewhere else. In NY they try oiling eggs to smother them and they have done some shooting, but to what end? Total extermination of a species doesn't seem like a bright idea to me.
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when there is a "surplus" of one species it points to a balance problem in nature, i.e. coyotes and rodents, owls and rodents, wolves and elk, etc. Eliminating the species only adds to the imbalance and we humans are already too proficient at that. imho
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Gardenfish,
All that you say is true. However, you didn't include we humans in that equation. Through our unimpeded growth, we destroy habitat, forests, build dams, etc. and throw the natural balance out of whack. Population shifts, creating farmlands, urban expansion forces the elimination or removal of natural preditors or habitat.
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"Shoot'em" A typical response when its not understood. There seem to be less fish and that bird eats fish... Then we start killing off the suckers for eating trout eggs, then the trout don't have young suckers to eat, and the remaining predator birds eat young trout 'cause there's no slower small fish to eat, then the trout populations crash and everybody complains that they have to pay taxes to stock more trout. Of course the whole time those few remaining birds are being shot 'cause they're eating the fish.
?Whats the natural predator of the cormorants anyways??? Pike, Muskie...?
If you want a good read about the amount of thought that Biologists are putting into this, read below.
From: [url=http://migratorybirds.fws.gov/issues/cormorant/greatlakes_facts.htm:2d564]http://migratorybirds.fws.gov/issues/cormorant/greatlakes_facts.htm[/url:2d564]
"The Great Lakes population of double-crested cormorants was devastated during the 1960s, primarily by the effects of chemical contamination especially DDT. Because they are fish-eating birds at the top of the food chain and long-lived (up to 20 years), adults accumulated pesticides and other toxins from the bodies of their prey. These chemicals caused reproductive failure, and chicks that hatched sometimes had crossed bills, club feet, and eye and skeletal deformities. In addition to contamination, human disturbance and nest destruction contributed to the decline.
In the early 1970s the Great Lakes population had plummeted, with few birds remaining or breeding successfully. In Wisconsin, the species was placed on the list of threatened and endangered wildlife. Nesting platforms were erected to aid their recovery. In 1972, double-crested cormorants were added to the list of species protected by the 1918 Migratory Bird Treaty Act. Despite these conservation efforts, the Great Lakes population continued to decline, with few breeding birds remaining or breeding successfully. The devastation of the Great Lakes cormorant population was a grim example of the declining health of the Great Lakes ecosystem.
A Population Resurgence
Today, the Great Lakes population of double-crested cormorants is at historic highs. Pollution control has lowered concentrations of toxic contaminants in their food supply, food is ample throughout their winter and summer ranges, and they are protected by federal and state laws. Nesting populations can be found on all the Great Lakes in both United States and Canadian waters, on inland lakes like Lake Champlain and Oneida Lake, and on the Niagara River.
Scientists do not expect the population to grow continuously. Instead, the number of birds should decline eventually, and then stabilize. Nesting habitat may become an important limiting factor. Disease may also play a role in this reversal. Although the cormorant population resurgence may indicate enhanced water quality in the Great Lakes, it has been accompanied by concern and controversy about the effects the birds may be having on stocks of recreational and commercial fish species, and island nesting habitat.
Issues
Because cormorants are conspicuous fish-eating birds, anglers in the Great Lakes basin may consider them a nuisance species and a threat to populations of recreational and commercial fish species. However, studies of the feeding habits of cormorants show the birds feed on many fish species, concentrating on the ones that are easiest to catch. Adult birds eat about one pound of fish per day. Because the ease with which a fish can be caught depends on such factors as distribution, relative abundance, and behavior, a cormorants?s diet can vary considerably from site to site and throughout the breeding and nesting seasons. All told, small (three to five inch) fish like alewife, yellow perch or gizzard shad provide most of their food. The birds find these fish in large schools, sometimes in shallow water.
Cormorants also feed on steelhead, lake and brown trout when available, especially when recently-stocked schools of small fish can be found in shallow near shore waters. Population level effects from cormorant predation on lake trout, salmon or steelhead are not apparent though, as diet studies indicate the birds consume very few of these fish in open waters. Can large colonies of cormorants reduce local populations of catchable-size pan fish like sunfish and rockbass, or sportfish like smallmouth bass, walleye pike, or yellow perch sufficiently to compete with anglers? Recreational and commercial anglers in some locations in the Great Lakes basin believe they can. Until biologists obtain additional information, the answer to this question remains unclear.
It is clear, though, that double-crested cormorants can feed heavily on small fish being raised commercially on minnow farms for bait, or for human consumption at fish farms or aquacultural sites. Also, in some locations within the Great Lakes basin, double-crested cormorants are competing with other colonial nesting water and wading birds for the same island nesting sites. A special concern exists when this competition jeopardizes the reproductive success of rare, threatened, or endangered plant and animal species."
In Canada: [url=http://www.on.ec.gc.ca/wildlife/factsheets/fs_cormorants-e.html:2d564]http://www.on.ec.gc.ca/wildlife/factsheets/fs_cormorants-e.html[/url:2d564]
"Too many Cormorants?
Fish harvesters have raised concerns about the rapid increase of cormorants and its potential effect on fish numbers in the Great Lakes. They fear that: 1) cormorants are competing with fish harvesters for large, major sport fish like Lake Trout and salmon; 2) the birds feed on the same prey fish which the large predatory fish need for food; and, 3) cormorants feed on and deplete local supplies of pan fish, such as perch and bass.
The first two concerns do not appear to be valid, since studies of cormorant diets in Lake Ontario show that less than 2% of the prey found in cormorant pellets is Lake Trout or salmon. Also, cormorants consume only about 0.5% of the prey fish, which is insignificant when compared to about 13% taken by sport fish.
The third concern is not such a clear issue. In northern Georgian Bay, fish harvesters feel that recent declines in local catches of yellow perch and smallmouth bass are the result of increased cormorant numbers at nearby colonies. As evidence they cite the ease with which a "meal" of fish was caught ten years ago, before the birds increased. Now, those fish are scarce and good catches are exceedingly rare. They also state that before cormorant numbers increased one could easily observe, when SCUBA diving, large and frequent schools of perch. These schools, too, have now disappeared.
Fish and wildlife officials do not currently have sufficient data to properly evaluate this problem. It is true that cormorant numbers have increased in northern Georgian Bay during the last decade. Cormorants do eat yellow perch and bass, and if these species were locally abundant, they could form the major part of their diet. The Ontario Ministry of Natural Resources and the Michigan Department of Natural Resources, with input from Environment Canada, are now undertaking a major study of the feeding habits of cormorants in Lake Huron in order to shed more light on this question.
There is also concern about the effect of cormorants on the vegetation in their nesting grounds. Cormorants can damage vegetation by stripping leaves from trees. The combined weight of the birds and their nests can even break branches. But perhaps most importantly, their excrement, which rains down to the ground from their nests, kills the ground vegetation and eventually kills the nest tree. In some cases, the loss of these trees can lead to increased erosion. This is of particular concern on sandspits and barrier beaches which protect interior wetlands. In other areas, the vegetation may be of unusual natural significance, such as the islands in western Lake Erie which are forested by rare stands of Carolinian woodlands. The large cormorant colonies there could seriously impact or even destroy this vegetation."
http://www.on.ec.gc.ca/wildlife/fact...m-graph6-e.gif
http://www.on.ec.gc.ca/wildlife/fact...m-graph2-e.gif
Had to come back and provide links to both sides of the issue... I hate not knowing both sides, I assume anybody really interested is the same.
[url=http://www.ofah.org/:2d564]http://www.ofah.org/[/url:2d564] and [url=http://www.osfn.ca/cormorants.html:2d564]http://www.osfn.ca/cormorants.html[/url:2d564]
Wow thats alot of stuff! http://www.flyanglersonline.com/bb/wink.gif
[This message has been edited by pharper (edited 11 February 2005).]
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A group of commercial fishermen going to kill a bunch of cormorants for making their living off of eating fish. Doesn't make sense to me. Unfortunately, there seems to be no end to the possessiveness and greed of man.
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Man has never done a good job of trying to balance nature, so hearing of groups that want to try scare me. Some folks blame artic terns (i think those are the right ones) for eating all the salmon smolt that get stunned while going through the Columbia River Dams, even blamed the squaw fish for eating all the smolt in the river system and still has a bounty on them. THe real problem is us peaple. We dam up the rivers, turn them into ditches with levees, pour toxic chemicals into them, and generaly destroy their habitat in our never ending need to develop the land into strip malls and planned communities. If cormorants are the real problem there, the problem would have already existed before Columbus accidently found north america! WE ARE THE PROBLEM. I am not sure that killing them off will do anything more than further upset the balance of nature. We need to realize that the balance of nature changes all on her own, despite what we want it to be like. Nature in this country did just fine taking care of herself before white man got here.
Jeff
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Last I checked, cormorants were migratory birds, protected by numerous laws. Depredation permits could very well be available for them, however. Yes, they eat fish, and in some areas, do contribute significantly to mortality of fish. However, blaming them for the decline of a fishery is rather narrow. Seldom is there ONE factor responsible for declines in populations of a species. In most cases, it is a combination of a lot of things, some of which have been listed above.
Shoot one of these in my presence, and you WILL be hearing from fish and game.
I once floated the Green in Utah with a guide. The first time we saw some mergansers, he got angry, and then told us a story about how a bunch of the river guides got together every winter and had merganser drives in the canyon. A bunch of boats would float down the canyon, herding the birds out in front of them, and more folks would be down at the takeout, and shoot them as they went by. Basically legal, since mergansers are ducks and can be hunted. (provided they are eaten, which I hear is not common). The guide was proud of all the ducks they slaughtered every winter.
My brother-in-law looked at me at the end of the story, and I at him, and neither of us said anything for a minute.
The guide, to fill the awkward silence, looked up at me and asked "So, what do you do for a living?"
"I'm a wildlife biologist" I replied.