04-25-2004, 04:56 AM
The Minnesota Department of Natural Resources (DNR), in conjunction with other resource management agencies, will take limited steps this summer to reduce local numbers of double-crested cormorants that may be affecting populations of walleye and other game fish.
The double-crested cormorant is an unprotected species under Minnesota law - meaning it could be taken with firearms or in several other ways - but it is protected by the federal government under the Migratory Bird Act.
Late last year, the U.S. Fish and Wildlife Service issued a rule that allows state, federal and tribal officials in 24 states, including Minnesota and Wisconsin, to control cormorants to prevent harm to fish species and other public resources. An earlier rule that allowed fish farmers to control birds in Minnesota and twelve southeastern states was expanded to allow federal officials to control birds on winter roosting sites.
"The new rule does two things," said Lee Pfannmuller, director of the DNR's Ecological Services Division. "One, it gives the DNR limited authority to manage certain double-crested cormorant problems. And two, it continues the federal government's regulatory management of the bird. The DNR, for example, cannot implement any control action that would kill more than ten percent of the double-crested cormorants in a breeding colony without the prior approval of the federal government."
The DNR and other resource management agencies will monitor and investigate cormorant populations in a number of locations this summer, including Knife River Island on Lake Superior, Leech Lake and Lake of the Woods. In addition to its focus in these three areas, the DNR is supporting a statewide survey of nesting cormorant colonies.
Double-crested cormorants are large dark birds that live throughout North America. The highest populations are found on the Great Lakes. The chemical DDT nearly wiped the birds out in the 1960s and '70s but they have made enough of a comeback to potentially affect fish populations and other public resources, according to the U.S. Fish and Wildlife Service.
The Migratory Bird Treaty Act prohibits killing birds such as cormorants except under specific circumstances and with federal authorization. Cormorant control actions in Minnesota are subject to approval by the federal government, which is responsible for managing their populations.
The DNR will likely seek approval for depredation control of the cormorant population on Knife River Island first. Approximately 100 birds nest on the island along the Lake Superior shoreline north of Duluth. The DNR will be working cooperatively with federal officials from the U.S. Department of Agriculture's Wildlife Services office in Grand Rapids on this project.
"It's likely that this cormorant colony feeds on young-of-the-year steelhead - rainbow trout - as they come down the Knife River," said Ron Payer, DNR fisheries chief. The DNR and Lake Superior Steelhead Association invest approximately $100,000 per year in stocking the young fish to supplement natural reproduction and are concerned that the investment has been jeopardized by the growth of this new colony. "We are going to examine the success of different actions to deter cormorant nesting and more closely examine what the birds are consuming. Because it's a small colony, it is likely that we can effectively reduce the local damage the birds may be causing," Payer said.
Initial efforts to control the Knife River Island population could include removing nesting material or harassing nesting birds with loud noises. Some adult birds also may be collected to analyze their stomach contents.
The cormorant population on Leech Lake -- approximately 1,100 pairs -- nests on Little Pelican Island, which is owned and managed by the Leech Lake Band of Ojibwe. Last year, the Band's natural resources department removed all nesting trees and nesting materials from Little Pelican to reduce cormorant breeding opportunities and protect the nesting common tern colony. "The DNR's first priority will be to support the tribe in these control measures and assess what impacts they might have on cormorants during the 2004 nesting season," Pfannmuller said. "We are investigating additional opportunities to collaborate with the Band on cormorant issues in the future."
Walleye fishing has been slow on Leech Lake in recent years, though there is no data to confirm or refute that cormorant populations are having an impact, Payer said. Poor walleye reproduction since 1997 and a strong hatch of yellow perch in 2002 have affected angler catch rates.
"Although cormorants have increased significantly on Leech Lake, we have observed comparable low points in the walleye population in past years when breeding cormorant colonies were not present on the lake," Payer said.
Action on Lake of the Woods will be limited to a population survey since the majority of cormorants nest on the Canadian side of the lake. "We'll need some time to collect data to assess the situation," Payer said.
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The double-crested cormorant is an unprotected species under Minnesota law - meaning it could be taken with firearms or in several other ways - but it is protected by the federal government under the Migratory Bird Act.
Late last year, the U.S. Fish and Wildlife Service issued a rule that allows state, federal and tribal officials in 24 states, including Minnesota and Wisconsin, to control cormorants to prevent harm to fish species and other public resources. An earlier rule that allowed fish farmers to control birds in Minnesota and twelve southeastern states was expanded to allow federal officials to control birds on winter roosting sites.
"The new rule does two things," said Lee Pfannmuller, director of the DNR's Ecological Services Division. "One, it gives the DNR limited authority to manage certain double-crested cormorant problems. And two, it continues the federal government's regulatory management of the bird. The DNR, for example, cannot implement any control action that would kill more than ten percent of the double-crested cormorants in a breeding colony without the prior approval of the federal government."
The DNR and other resource management agencies will monitor and investigate cormorant populations in a number of locations this summer, including Knife River Island on Lake Superior, Leech Lake and Lake of the Woods. In addition to its focus in these three areas, the DNR is supporting a statewide survey of nesting cormorant colonies.
Double-crested cormorants are large dark birds that live throughout North America. The highest populations are found on the Great Lakes. The chemical DDT nearly wiped the birds out in the 1960s and '70s but they have made enough of a comeback to potentially affect fish populations and other public resources, according to the U.S. Fish and Wildlife Service.
The Migratory Bird Treaty Act prohibits killing birds such as cormorants except under specific circumstances and with federal authorization. Cormorant control actions in Minnesota are subject to approval by the federal government, which is responsible for managing their populations.
The DNR will likely seek approval for depredation control of the cormorant population on Knife River Island first. Approximately 100 birds nest on the island along the Lake Superior shoreline north of Duluth. The DNR will be working cooperatively with federal officials from the U.S. Department of Agriculture's Wildlife Services office in Grand Rapids on this project.
"It's likely that this cormorant colony feeds on young-of-the-year steelhead - rainbow trout - as they come down the Knife River," said Ron Payer, DNR fisheries chief. The DNR and Lake Superior Steelhead Association invest approximately $100,000 per year in stocking the young fish to supplement natural reproduction and are concerned that the investment has been jeopardized by the growth of this new colony. "We are going to examine the success of different actions to deter cormorant nesting and more closely examine what the birds are consuming. Because it's a small colony, it is likely that we can effectively reduce the local damage the birds may be causing," Payer said.
Initial efforts to control the Knife River Island population could include removing nesting material or harassing nesting birds with loud noises. Some adult birds also may be collected to analyze their stomach contents.
The cormorant population on Leech Lake -- approximately 1,100 pairs -- nests on Little Pelican Island, which is owned and managed by the Leech Lake Band of Ojibwe. Last year, the Band's natural resources department removed all nesting trees and nesting materials from Little Pelican to reduce cormorant breeding opportunities and protect the nesting common tern colony. "The DNR's first priority will be to support the tribe in these control measures and assess what impacts they might have on cormorants during the 2004 nesting season," Pfannmuller said. "We are investigating additional opportunities to collaborate with the Band on cormorant issues in the future."
Walleye fishing has been slow on Leech Lake in recent years, though there is no data to confirm or refute that cormorant populations are having an impact, Payer said. Poor walleye reproduction since 1997 and a strong hatch of yellow perch in 2002 have affected angler catch rates.
"Although cormorants have increased significantly on Leech Lake, we have observed comparable low points in the walleye population in past years when breeding cormorant colonies were not present on the lake," Payer said.
Action on Lake of the Woods will be limited to a population survey since the majority of cormorants nest on the Canadian side of the lake. "We'll need some time to collect data to assess the situation," Payer said.
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