Some smallmouth bass fisheries are on fire these days—hotter than a green-chile cheeseburger, especially those in the mid- and northern portions of their range. Nowhere is this more apparent than around the Great Lakes, where fish in the 6- and 7-pound class have become almost common.
When the Sturgeon Bay Open bass tournament on the Wisconsin portion of Lake Michigan’s Green Bay was held in 1992, the winning team bagged an average fish of 2.99 pounds. Last year the winning bag averaged 5.36 pounds per fish—the 2.99-pound average would have placed 134th among 193 teams.
It’s not just the occasional bragging-size bulldog that anglers are catching. So many big bass are coming to net in places like Lake Erie, eastern Lake Ontario, Lake St. Clair, and Lake Michigan that anglers wonder where it might end. Are 8- and 9-pound fish possible? How about a new world record?
But we must consider the flip side of this sensation. We also worry about an apparent lack of small bass in Great Lakes waters these days. Others fear booming populations of fish-eating birds could curtail smallmouth fisheries. And round gobies continue to spread. What does science suggest about the future of smallmouth fisheries?
Could Cormorants Cause a Crash?
Equipped with natural wetsuits and unique eyes that allow them to dive deep to catch fleeing fish, double-crested cormorants are generally seen as trouble makers—especially when fish populations wane. Though they’re naturally occurring across much of North America—flocks of cormorants were reported on Lake of the Woods as early as the 1700s—the birds remain an obnoxious mystery to most anglers.
Breeding colonies around the Great Lakes didn’t become established until the early 1900s. There were only 14 nests on Lake Erie in 1945, when the first colony was sighted. In the 1960s and 1970s, populations were decimated by chemically induced reproductive failure. When the pesticide DDT was subsequently banned, cormorant numbers expanded rapidly to a continental population estimated more than 2 million. Many anglers and some fishery agencies believe they damage fisheries by eating gamefish along with enormous quantities of baitfish.
In eastern Lake Ontario, New York State Department of Environmental Conservation officials determined that the diet of 8,000 nesting pairs of cormorants was primarily coarse fish like alewives and sticklebacks. Only one percent of their diet was bass, with smallmouth up to 12 inches occasionally eaten. But that’s still a loss of 1.3 million smallmouths a year. Moreover, bass populations appeared to be thriving in portions of Lake Ontario where cormorant activity was negligible or non-existent.
To put the fish-eating skills of the Little Galloo Island cormorant colony into perspective, scientists determined that since 1992, the birds have, “consumed about 349 million fish, weighing about 33 million pounds, including 116 million alewife, 88 million yellow perch, 44 million cyprinids, 24 million pumpkinseed, 21 million rock bass, and 13 million smallmouth bass. Of these species, predation by cormorants has been tied to declines in smallmouth bass and yellow perch.”
Meanwhile, Cornell University researchers documented a similar link at Oneida Lake in New York between increasing cormorant numbers and dwindling yellow perch and walleye stocks. The birds were nonexistent on Oneida prior to 1983, whereas today 500 adults nest on Wantry and Long islands. Those numbers are augmented in autumn by as many as 2,000 cormorants that visit the lake during their fall migration.
A similar connection has been drawn on Minnesota’s Leech Lake, where more than 2,500 cormorants a year have been culled for four years in a row. Regional fishery manager Henry Drewes said the measure hastened the recovery of walleyes and perch in Leech Lake. Curiously, that lake’s largemouth bass increased as the walleyes and perch declined. Leech Lake doesn’t contain smallmouth bass.
Just as at lakes Ontario and Oneida, Leech Lake walleye and perch populations were crashing at the same time the cormorants were booming. When cormorant numbers were controlled, sportfish populations rebounded quickly. A recent fall walleye netting index recorded the second highest catch since sampling began there over 25 years ago. The same trend held true for the perch, which soared from historic low to historic high at Leech Lake as soon as cormorant numbers fell.
But lakes like Ontario, and even Oneida and Leech are large. What happens when cormorant flocks are driven inland, say in advance of an approaching storm, and ride out the system on a small lake? It’s conceivable, says Ontario Ministry of Natural Resources researcher, Dr. Mark Ridgway, that the birds could eat a significant portion of the lake’s annual allowable harvest of sportfish in just days.
Ridgway recently completed the largest research experiment conducted in the Great Lakes when, over the course of several years, he studied the connection between the cormorant population on Lake Huron and the fish community. “Many people originally believed,” he says, “that the birds controlled their density in concert with their food supply. That is, if they impacted a specific fish, that species would compensate by reproducing and growing faster. But that’s not what we found.
“Cormorants are predators that consume enormous quantities of fish, especially schooling species like perch. At high density, they can control entire nearshore fish communities. In parts of Lake Huron we found they consumed 3 to 5 times the annual sustainable yield.”
Ridgway uses the past tense to describe the impact of cormorants on Lake Huron, as the alewife population, the bird’s principle food source, recently crashed and cormorant numbers have fallen by one third. “Nature beat us on that one,” he says.
