Cormorant management is making strides in reducing the population
Lansing — More than 10,000 double-crested cormorants were killed last year in Michigan through an ongoing effort to manage the burgeoning population of the fish-eating birds and protect vulnerable game fish populations at key times of the year. Adult cormorants are known to eat about a pound of fish per day. When thousands of cormorants descend on spawning waters of game fish in the spring and fall, significant damage occurs to local fisheries, studies have shown.
Colony management and harassment activities – which both include the killing of a limited number of cormorants by state and federal officials – are allowed under a federal depredation order, which is scheduled to expire next month. But based on the success of the order, and continued problems with cormorant overpopulation, state officials expect that order to be extended and the cormorant management battle to continue.
Because cormorants are migratory birds, they’re managed at the federal level by the U.S. Fish and Wildlife Service.
“They (USFWS) have drafted an EA (environmental assesment) to extend the depredation order for five years. We’re optimistic the depredation order won’t lapse,” Karen Cleveland, the DNR’s all-bird biologist, told the state Natural Resources Commission at its meeting May 8 in Lansing.
Despite the wishes of many anglers to kill every cormorant in sight, management is more of a balancing act, according to Cleveland.
“At the end of the day, we’re not shooting cormorants just to shoot cormorants. We’re shooting them to manage the fisheries,” Cleveland told Michigan Outdoor News. “Cormorants were endangered in the 1980s. Now they’re on the protected list. We don’t want them to become endangered again.”
Harassment activities target cormorants that are migrating through, but are not nesting in Michigan. Colony management targets cormorants that are nesting in Michigan.
Colony management accounted for the lion’s share of dead cormorants last year, when 7,520 birds were killed and 1,167 nests were oiled to kill cormorant eggs. Harassment efforts netted another 2,646 dead cormorants.
Since 2007, the number of cormorant nests in Michigan has been reduced by 34.5 percent, according to Cleveland. The total nest count stands at about 19,000, down from around 29,000. She said the goal of the program is to reduce nest numbers to between 5,000 and 12,000 across the state.
“We’ve been at it for a decade now and we have made some significant progress,” said Steve Scott, a DNR fisheries manager from Newberry in the Upper Peninsula.
For instance, in 2004 when Michigan’s cormorant control program began, there were an estimated 4,600 nests in the Les Cheneaux Islands in Mackinac County. The goal was to reduce that population to 500 nests, and that goal was realized last year, Scott said. Other areas with significant reductions in cormorant nests include: Thunder Bay, down 80 percent; Beaver Island, down 69 percent; and Bays de Noc, down 54 percent.
Despite the apparent success of the program, some areas, like at the Ludington Pump Facility in Mason County, continue to be impacted by the fish-eating birds.
“The problem is that there is just a meca of birds both inside and outside the barrier at Ludington,” Scott said. “That’s the last island before they leave Lake Michigan from the north.”
Scott said some 900 birds were killed at Ludington one day last year, “and the next day they couldn’t see a difference. It’s a fall migration stop, and they get a lot of birds over there.”
Cleveland said the management goal is not measured in dead cormorants; rather it’s measured in fisheries response, and those measurements show positive results.
In areas where nest numbers have been reduced to near target levels, fish have responded. At the Les Cheneaux Islands – where a world-class yellow perch fishery was decimated by cormorants – the number of older perch has risen, the catch per effort by anglers is up, and the average size of perch is up, according to Scott. “What has come back rather slowly is angler harvest,” he said. “There aren’t as many people fishing for them now as back in the day.”
It’s not just perch that are rebounding. Scott said that in addition to perch numbers being up in both Big and Little Bays de Noc since cormorant reduction began there in 2004, walleye numbers are up in Little Bay de Noc and smallmouth bass numbers are up in Big Bay de Noc.
On Lake Huron, the number of steelhead caught and the catch per effort have both improved at all ports. “There is speculation that reduced cormorant numbers may be a part of that,” Scott said.
According to Cleveland, cormorant management activities will continue in 2014 as long as the federal depredation order is extended. They’ll include further reduction of breeding colonies at Ludington, the Les Cheneaux Islands, Thunder Bay, Beaver Island, and Bays de Noc; continuation of a diet study on Saginaw Bay to see exactly what the cormorants are eating there; and protection of black-horned night herons at Pointe Mouillee State Game Area on Lake Erie and protection of herons and egrets at Crow Island SGA in Saginaw and Bay counties.