April 13, 2012
Smallmouth bass fisheries are on fire these days — hotter than a chili cheeseburger, especially those in the northern parts 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's average fish weighed 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 Lake Erie, eastern Lake Ontario, Lake St. Clair, Lake Michigan, and select inland waters that anglers wonder where it might end. Are 8- and 9-pounders possible? A new world record?
We must also consider the flip side of this sensation. There's worry about an apparent lack of small bass in Great Lakes waters. 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 banned, cormorant numbers expanded to a continental population estimated at more than 2 million. Many anglers and fishery experts believe they damage fisheries by eating gamefish and 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 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. 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 annually. 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 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.
Goby Numbers Surge
Nature isn't likely to make a dent on the round goby population in the Great Lakes. This invasive species continues to thrive in some of the world's best smallmouth fisheries. Ontario scientists pegged the goby population in Lake Erie's western basin at more than 8 billion fish. And this species has spread inland, colonizing new bodies of water.
Most Great Lakes anglers can hardly believe their good fortune these days, as they catch more and bigger bass. Clearly, adult bass are gorging on gobies and prospering. But do tables turn in spring when smallmouths are bedding? Are gobies gobbling up too many bass eggs?
A group of Ohio State University researchers led by Geoffrey Steinhart sought to answer that question by monitoring what happens when anglers catch nesting male smallmouths on Erie. While one team member hooked a bedding bass, another, wearing scuba gear, measured the rate at which gobies ate the unprotected eggs.
On average, three gobies started eating eggs as soon as the nest was unguarded. Factoring in elapsed time between catching the fish and releasing it to return to the nest, Steinhart estimated that 400 eggs are eaten every time an angler pulls a bass from its bed. With such a large bass population, however, effects on bass recruitment are unlikely.
There are so many gobies in the Great Lakes that Steinhart estimates the males in Lake Erie spend 15 times more energy protecting their broods than bass in lakes where no gobies exist.
Great Lakes weather systems bring another complicating factor. Spring storms with winds over 16 miles an hour are the norm on lakes like Erie. According to Steinhart, they can wash out 90 percent of the eggs in a smallmouth nest in two hours, making life even sweeter for the gobies. Could the best smallmouth bass fishery on the planet be in trouble before long?
Surprisingly, "no", says Ridgway, who has studied smallmouth bass populations perhaps more than any other scientist. "Lake Erie has a bass profile unlike any other water. The fish are bigger than ever before. While there may be fewer small bass, survival and growth rates are phenomenal. Smallmouths eat gobies like candy, but they're apparently nutritious."
Ridgway says that the age composition of most bass populations resembles a pyramid, with most of the fish — the foundation of the pyramid — comprised of the youngest members. The pyramid then takes its familiar shape with ever fewer fish in older age groups. But Lake Erie's population pyramid is inverted, with fewer small fish and ever growing numbers of older, gargantuan bass.
And consider inland waterways near the Great Lakes, like southern Ontario's Lake Simcoe, where 5-fish catches of smallies weighing 25 pounds aren't unusual. Now that gobies have invaded the lake, might they wreck havoc with the bass population?
Ridgway says that might have been the case a decade ago. But now a powerful new buffer is at work, in the form of climate change and global warming. "Across North America, but especially in the northern portion of the smallmouth's range, lakes are warming earlier in spring," he notes. "We're seeing 30 percent more smallmouth nests in our study lakes now than we saw in the 1990s, and survival rates are higher.
"So, on one hand, weather and water conditions seem more favorable for smallmouth bass, while on the other, gobies are a new and plentiful food source. Even if reductions are caused by goby nest invasion, we're still seeing net gains for bass. That's not the case for all species, but for smallmouths, it appears that gobies aren't knocking them down as fast as climate variation raises them up."
An Ever Changing Game
Ridgway recently began noticing a new trends in bass spawning in his Algonquin Park study lakes. Nests there now contain about half as many eggs as they did a few years ago.
"A decade ago, it was common to observe a male smallmouth guarding 1,000 free-swimming fry," he says. "Six hundred fry was a low count. Today, 600 is average. The eggs are as big as they've ever been and male size distribution is the same. Nest density and fry survival have increased."
Ridgway says that a few years ago, he would have observed 50 to 70 male smallmouths protecting nests along a major section of shoreline. Today, he finds 120 to 130 nesting males along the same stretch but nests have fewer eggs. "The net effect on reproduction is insignificant," he says. "The population is growing by different means."
Despite a complicated ecology, the future for smallmouth bass in most regions continues to look rosy — make that golden bronze.
*In-Fisherman Field Editor Gord Pyzer, Kenora, Ontario, has been writing about smallmouth bass for almost two decades.