Hamilton Reef
06-12-2006, 10:57 PM
Curse of the cormorant
Role of once-threatened bird in chinook demise under study
http://www.mlive.com/outdoors/fljournal/index.ssf?/base/sports-1/1149861009268930.xml&coll=5
THE FLINT JOURNAL FIRST EDITION Thursday, June 08, 2006
By Elizabeth Shaw eshaw@flintjournal.com • 810.766.6311
Local anglers have their eyes on the sky in an effort to save Lake Huron's salmon.
The Flint River Valley Steelheaders' new Cormorant Control and Research Fund hopes to address the migratory bird's possible role in the recent decline of chinook salmon in the Great Lakes region.
The birds have been blamed for eating up the perch population and threatening other fish species in the Great Lakes from the western Upper Peninsula to the Thunder Bay area near Alpena.
The Steelheaders and others fear the birds also may be consuming what's left of Lake Huron's dwindling food supply for salmon.
"Cormorant aren't the only cause for the decline, but they're one of the biggest players and something we can actually do something about," said Norman Anderson, Steelheaders president. "Our goal is to get everybody who has a stake in this to contribute. It's not just the fishermen. What happens in the Great Lakes affects tourism and everything else in Michigan."
Federal and state agencies have been working together for three years on cormorant management at nesting and feeding sites in the northern regions of lakes Huron and Michigan.
The link isn't conclusive, but early signs seem to indicate the work is having a positive effect.
But not everyone agrees those efforts should be extended farther south into Lake Huron, where some say the birds are being prematurely blamed, with no firm evidence linking them to fishery declines in the Saginaw Bay area.
The new fund could help solve the impasse by bankrolling research needed to get those answers.
"No one has studied cormorant foraging in Saginaw Bay. Fisheries are a very dynamic, interwoven system so it may be impossible to sort it all out," said Pete Butchko, state director of the U.S. Department of Agriculture Wildlife Services. "The Steelheaders realize it's going to take some money to solve this, and they want to be part of the solution. That's why they're providing the money with no strings attached."
Shrinking salmon
Just four years ago, Lake Huron anglers saw the best chinook harvest in nearly two decades. Ironically, that "good news" actually was a red-flag warning of the drastic downturn to come.
According to biologists, big increases in the catch rate can mean too many hungry fish desperate to eat anything, including anglers' lures. By 2005, the warning had brewed into reality.
Recent studies by the state Department of Natural Resources have shown a major decline in the Lake Huron salmon fishery, with reduced catch rates and many of the remaining salmon extremely underweight. Some mature salmon are weighing in at less than 10 pounds, compared to the normal range of 30-40 pounds and 38 inches in length.
"It's obvious, even if you don't know anything about the science," said the Steelheaders' Anderson. "When you bring in a fish that should weigh 20 pounds, and it's eight or 10 pounds, that tells you something is really, really wrong in the lake."
What's gone wrong is a complicated mix of factors shaking up the lake's food chain, including a decline in baitfish forage and an increase in invasive species and fish-eating predators.
Knocking the predator-prey ratio even further off-balance is the increased survival rate of lake trout in recent years, thanks to successful sea lamprey control in 2001 and a change to less lethal commercial fishing nets in 2000. More salmon have been reproducing in the wild, too.
How heavily each of those factors weighs is a subject for debate among state and federal experts as well as anglers and wildlife advocates.
But it all boils down to not enough food to support the existing salmon population, resulting in fewer and smaller salmon surviving to adulthood.
The DNR has responded by reducing the stocking of Lake Huron salmon by 50 percent to help restore balance with the food supply, while continuing to monitor the other factors.
The stock reduction is supported by the Steelheaders and the Lake Huron Citizens' Advisory Committee. But some don't feel it's enough to turn the tide.
"The salmon almost look anorexic because they're not getting the feed they need," said Anderson. "Everybody who has dealt with this finds it frustrating the DNR is not doing more."
Fish food
The key issue is the disappearance of the alewife, the salmon's primary food source.
A non-native species, the alewife is vulnerable to Michigan cold so their numbers can vary dramatically with weather extremes. The harsh winters of 2002-03 slashed alewife numbers to a third or even half their former 12-year average.
Usually, when the alewives die back, the populations of smelt and other baitfish increase to fill the gap. But that failed to happen this time, leading to a food shortage for salmon by 2004.
So what else went wrong?
Back in the late 1980s, zebra mussels and other invasives first entered the Great Lakes via shipping channels. Before long, the invasives were devouring the nutrients at the bottom of the lake, clearing the water and leaving little for baitfish to eat.
No one disputes the impact.
"Our entire Great Lakes are infested. The clarity in the water is unbelievable," said Anderson. "They've totally changed the way the lakes are fished."
By the time the cormorant issue surfaced, it was just one more assault on an already weakened system.
The cormorant question
During the 1960s, the double-breasted cormorant was itself threatened by pesticides and other factors. But the population has boomed since its protection under the federal Migratory Bird Act in 1972
Michigan now has approximately 28,000 nesting pairs, not including juveniles and migratory flocks. Peak numbers could be 10-33 percent higher, said Butchko.
An adult cormorant eats almost 1.5 pounds of live fish per day, adding up to about 1.5 million pounds of Michigan fish every year, said Jim Johnson, a state DNR fisheries biologist based in Alpena.
By 2000, the birds appeared to be eating nearly as much fish as the waters around several northern Michigan communities could produce. Spawning yellow perch were being gobbled up in the Les Cheneaux area, while brown trout were eaten up almost as quickly as they were stocked in Thunder Bay.
"The Alpena brown trout festival has taken a real beating. The amount and poundage coming out of Thunder Bay is really scary," said Anderson. "That's what we don't want to see here."
In 2000, experts estimated cormorants were eating about 18 percent of Lake Huron's annual alewife production.
"But now the question has changed," said Johnson. "Now that there are no alewives, my concern is: What are they eating now?"
The birds are notoriously nonpicky when in comes to their diets, Johnson said, and will eat anything available. As proof, he points to the Thunder Bay area, where the fishery has thinned from 20-30 pounds an acre to about a pound an acre.
"If we could've seen this coming in Thunder Bay, we might have turned it around," he said. "We haven't seen a decline in trawl catches yet in the Saginaw Bay area, but it's probably going to take a pretty sizable hit by the time it drops to the point where we can really measure it."
Saginaw Bay currently has a cormorant rookery on Little Charity Island, managed by the Shiawassee National Wildlife Refuge. The refuge also manages Scarecrow Island in the Thunder Bay region. Refuge manager Steven Kahl has not allowed access to either rookery for a control program.
"We haven't been given the data that strongly links the cormorant with the declining fishery. No dietary analysis has been done to determine what they're actually eating," said Kahl. "If any academic researcher wants permission to conduct that analysis on our islands, we'd permit that.
"This is the place where we have to maintain a higher standard of scientific justification. Right now, the burden of proof is on them."
Johnson and Butchko agreed, but said their program lacks the money to do that.
All said the new Steelheaders fund may be the solution.
"Any issue of this scope has its percentage of people who want to react quicker without enough data to back it up," said Kahl. "I'm sure we're all in favor of any research that helps clear up those question marks."
Role of once-threatened bird in chinook demise under study
http://www.mlive.com/outdoors/fljournal/index.ssf?/base/sports-1/1149861009268930.xml&coll=5
THE FLINT JOURNAL FIRST EDITION Thursday, June 08, 2006
By Elizabeth Shaw eshaw@flintjournal.com • 810.766.6311
Local anglers have their eyes on the sky in an effort to save Lake Huron's salmon.
The Flint River Valley Steelheaders' new Cormorant Control and Research Fund hopes to address the migratory bird's possible role in the recent decline of chinook salmon in the Great Lakes region.
The birds have been blamed for eating up the perch population and threatening other fish species in the Great Lakes from the western Upper Peninsula to the Thunder Bay area near Alpena.
The Steelheaders and others fear the birds also may be consuming what's left of Lake Huron's dwindling food supply for salmon.
"Cormorant aren't the only cause for the decline, but they're one of the biggest players and something we can actually do something about," said Norman Anderson, Steelheaders president. "Our goal is to get everybody who has a stake in this to contribute. It's not just the fishermen. What happens in the Great Lakes affects tourism and everything else in Michigan."
Federal and state agencies have been working together for three years on cormorant management at nesting and feeding sites in the northern regions of lakes Huron and Michigan.
The link isn't conclusive, but early signs seem to indicate the work is having a positive effect.
But not everyone agrees those efforts should be extended farther south into Lake Huron, where some say the birds are being prematurely blamed, with no firm evidence linking them to fishery declines in the Saginaw Bay area.
The new fund could help solve the impasse by bankrolling research needed to get those answers.
"No one has studied cormorant foraging in Saginaw Bay. Fisheries are a very dynamic, interwoven system so it may be impossible to sort it all out," said Pete Butchko, state director of the U.S. Department of Agriculture Wildlife Services. "The Steelheaders realize it's going to take some money to solve this, and they want to be part of the solution. That's why they're providing the money with no strings attached."
Shrinking salmon
Just four years ago, Lake Huron anglers saw the best chinook harvest in nearly two decades. Ironically, that "good news" actually was a red-flag warning of the drastic downturn to come.
According to biologists, big increases in the catch rate can mean too many hungry fish desperate to eat anything, including anglers' lures. By 2005, the warning had brewed into reality.
Recent studies by the state Department of Natural Resources have shown a major decline in the Lake Huron salmon fishery, with reduced catch rates and many of the remaining salmon extremely underweight. Some mature salmon are weighing in at less than 10 pounds, compared to the normal range of 30-40 pounds and 38 inches in length.
"It's obvious, even if you don't know anything about the science," said the Steelheaders' Anderson. "When you bring in a fish that should weigh 20 pounds, and it's eight or 10 pounds, that tells you something is really, really wrong in the lake."
What's gone wrong is a complicated mix of factors shaking up the lake's food chain, including a decline in baitfish forage and an increase in invasive species and fish-eating predators.
Knocking the predator-prey ratio even further off-balance is the increased survival rate of lake trout in recent years, thanks to successful sea lamprey control in 2001 and a change to less lethal commercial fishing nets in 2000. More salmon have been reproducing in the wild, too.
How heavily each of those factors weighs is a subject for debate among state and federal experts as well as anglers and wildlife advocates.
But it all boils down to not enough food to support the existing salmon population, resulting in fewer and smaller salmon surviving to adulthood.
The DNR has responded by reducing the stocking of Lake Huron salmon by 50 percent to help restore balance with the food supply, while continuing to monitor the other factors.
The stock reduction is supported by the Steelheaders and the Lake Huron Citizens' Advisory Committee. But some don't feel it's enough to turn the tide.
"The salmon almost look anorexic because they're not getting the feed they need," said Anderson. "Everybody who has dealt with this finds it frustrating the DNR is not doing more."
Fish food
The key issue is the disappearance of the alewife, the salmon's primary food source.
A non-native species, the alewife is vulnerable to Michigan cold so their numbers can vary dramatically with weather extremes. The harsh winters of 2002-03 slashed alewife numbers to a third or even half their former 12-year average.
Usually, when the alewives die back, the populations of smelt and other baitfish increase to fill the gap. But that failed to happen this time, leading to a food shortage for salmon by 2004.
So what else went wrong?
Back in the late 1980s, zebra mussels and other invasives first entered the Great Lakes via shipping channels. Before long, the invasives were devouring the nutrients at the bottom of the lake, clearing the water and leaving little for baitfish to eat.
No one disputes the impact.
"Our entire Great Lakes are infested. The clarity in the water is unbelievable," said Anderson. "They've totally changed the way the lakes are fished."
By the time the cormorant issue surfaced, it was just one more assault on an already weakened system.
The cormorant question
During the 1960s, the double-breasted cormorant was itself threatened by pesticides and other factors. But the population has boomed since its protection under the federal Migratory Bird Act in 1972
Michigan now has approximately 28,000 nesting pairs, not including juveniles and migratory flocks. Peak numbers could be 10-33 percent higher, said Butchko.
An adult cormorant eats almost 1.5 pounds of live fish per day, adding up to about 1.5 million pounds of Michigan fish every year, said Jim Johnson, a state DNR fisheries biologist based in Alpena.
By 2000, the birds appeared to be eating nearly as much fish as the waters around several northern Michigan communities could produce. Spawning yellow perch were being gobbled up in the Les Cheneaux area, while brown trout were eaten up almost as quickly as they were stocked in Thunder Bay.
"The Alpena brown trout festival has taken a real beating. The amount and poundage coming out of Thunder Bay is really scary," said Anderson. "That's what we don't want to see here."
In 2000, experts estimated cormorants were eating about 18 percent of Lake Huron's annual alewife production.
"But now the question has changed," said Johnson. "Now that there are no alewives, my concern is: What are they eating now?"
The birds are notoriously nonpicky when in comes to their diets, Johnson said, and will eat anything available. As proof, he points to the Thunder Bay area, where the fishery has thinned from 20-30 pounds an acre to about a pound an acre.
"If we could've seen this coming in Thunder Bay, we might have turned it around," he said. "We haven't seen a decline in trawl catches yet in the Saginaw Bay area, but it's probably going to take a pretty sizable hit by the time it drops to the point where we can really measure it."
Saginaw Bay currently has a cormorant rookery on Little Charity Island, managed by the Shiawassee National Wildlife Refuge. The refuge also manages Scarecrow Island in the Thunder Bay region. Refuge manager Steven Kahl has not allowed access to either rookery for a control program.
"We haven't been given the data that strongly links the cormorant with the declining fishery. No dietary analysis has been done to determine what they're actually eating," said Kahl. "If any academic researcher wants permission to conduct that analysis on our islands, we'd permit that.
"This is the place where we have to maintain a higher standard of scientific justification. Right now, the burden of proof is on them."
Johnson and Butchko agreed, but said their program lacks the money to do that.
All said the new Steelheaders fund may be the solution.
"Any issue of this scope has its percentage of people who want to react quicker without enough data to back it up," said Kahl. "I'm sure we're all in favor of any research that helps clear up those question marks."