Great Lake Trout Trends
December 06, 2011
Long before salmon reigned as king, lake trout ruled North America's largest lakes. Before Columbus, Native Americans plied the Great Lakes for lake trout in birch-bark canoes, using rocks to carry their baits deep with lines made of gut, hair, or both. Apparently, they even fashioned lures from clam shells.
Wire lines and heavy weights were the rule for open-water lake trout anglers from Victorian times until downriggers were invented in the 1960s. Commercial fisheries depended on sailboats and row boats to lift nets until 1906 when wooden steamers took over. The peak commercial harvests of lake trout from lakes Huron and Michigan took place between 1892 and 1896. During that period, an estimated 34.8 million pounds of lake trout were extracted from Lake Michigan by all commercial sources — almost 7 million pounds per year, and by far the most ever netted in any five-year period from any of the Great Lakes.
Ships and the nets they carried continued to increase in efficiency into the 1950s, when a general collapse occurred in lake trout fisheries throughout the Great Lakes. In 1951, total commercial harvest from Lake Michigan dropped to 7,000 pounds, then to 3,000 pounds in 1952. Did commercial fishing doom the lake trout?
In 1968 the Fisheries Research Board of Canada reported that "the famous lake trout fisheries of the Great Lakes have been decimated by the sea lamprey and by pollution, particularly DDT. The latter accumulates in fatty tissues, especially in the yolk of the egg and induces the death of the embryo following yolk absorption." Little did they realize that another toxic chemical 200 times deadlier than DDT was already at large in the lakes.
Lake Erie had a thriving community of lakers prior to 1950. That line of genetic lineage is now gone. According to Mary Burnham-Curtis of the National Biological Service, the native lake trout of Lake Ontario also became extinct, "and no remnant stocks exist." All native strains of lake trout within Lake Michigan "are now extinct, and no remnant stocks exist." Lake Huron's native lakers were "severely reduced," and only a few remnant populations persist in Georgian Bay. The lake trout fisheries in Lake Superior collapsed in the 1950s, too, but the cooperative management efforts of bordering states and Ontario salvaged some native strains from the extinction parade.
Lake trout never made the list of endangered species, however, because they remain plentiful elsewhere on the continent. So, with plenty of stocks to work with, the "good" news is that lake trout numbers are high again in Lake Michigan and in Lake Ontario.
In fact, an In-Fisherman television crew visited the famous Niagara Bar on Lake Ontario last year for one of its easiest filming missions. Lake trout carpet the bottom on the Bar all winter long. A live shiner on a simple bait rig is mauled before it reaches bottom. Lake trout average 8- to 12-pounds, with plenty in the 20-pound class. It easily rivals most fly-in camps in Canada for both numbers and size. Lake trout fishing across Lake Ontario and Lake Michigan is good to spectacular for big fish. So, what's the problem?
The problem stems from the almost complete lack of natural reproduction in all but one of the Great Lakes. Other problems stem from replacing extinct genetic strains with strains of fish adapted to other environments. A study by the Ontario Ministry of Natural Resources called Loss of Exploited, Indigenous Populations of Lake Trout by Stocking of Non-Native Stocks, by David Owens and Campbell Wilcox, concluded: "Simulation modeling generally supported our two main hypotheses: 1. That stocking of hatchery-reared lake trout results in the loss of native stocks; and 2. That high fishing mortality accelerates the rate of displacement of native stocks by hatchery stocks."
When stocking of non-native strains of trout exceeds natural reproduction by wild fish, the study warns, wild stocks will eventually disappear due to the sheer weight of numbers, even if no interbreeding occurs. Moreover, when a native trout breeds with a hatchery trout, the resulting genetic mix is compromised. In some ways, the hatchlings are weaker and less adapted to their environments than indigenous fish. A third danger exists: Because lake trout live in deep, clear, relatively sterile environments, they often resort to cannibalism. When non-native adults are stocked, the study reports, cannibalism increases. Wild hatchlings are high on the menu because they're easy for hatchery fish to find and prey upon. Hatchery fish are notoriously poor at capturing wild adult baitfish like ciscoes when first stocked.
From a study called Lake Trout Populations In Lake Superior and Their Restoration, 1959-1993 by Michael Hansen of the National Biological Service: "Diverse lake trout forms persisted in Lake Superior until the 1950s, when excessive fishery (both sport and commercial) exploitation and sea-lamprey predation destroyed all but a few. Restoration efforts began in time to save a few stocks of offshore lean, siscowet and humper lake trout, but virtually all stocks of inshore-lean lake trout were eliminated. Genetic diversity was thus greatly reduced by destruction of locally adapted stocks, interbreeding between stocked and wild lake trout, and introgression between formerly isolated wild stocks."
Fortunately, biologists found a lake in Wisconsin stocked many years ago with Lake Michigan trout. Lake Huron retains a remnant strain or two to work with. So, hopes of reestablishing a viable native population in those lakes persists. But beating back the lamprey invasion and controlling harvest won't solve the reproduction problem. According to a recent EPA report on POPs (Persistent Organic Pollutants), "Studies during the early 1980s by scientists at the U.S. Fish and Wildlife Service (FWS) in Ann Arbor, Michigan, indicated that the most likely cause of poor reproductive success (among lake trout) was toxic chemicals. Their analyses identified 167 chlorinated hydrocarbons in fish, and many more have been identified since."
Back in the 1960s, the insecticide DDT was found poisonous to hatchling lake trout. Some PCBs (polychlorinated biphenyls) were later found to be even more toxic to lakers. More recently, scientists working for the Sea Grant program discovered that lake trout hatchlings die in the presence of tiny amounts (200 times less than the deadliest PCB) of a form of dioxin that has been pumped into all the Great Lakes in the form of industrial and municipal waste for over 100 years.
According to a recent study by Sea Grant, the fate of at least one Great Lakes gray-trout population was sealed by 1940. The usual suspects — the oft-damned lamprey invasion, commercial fishing pressure, DDT and PCBs — were lined up, but didn't take the fall this time. Something else was fingered for the hit that sent Lake Ontario trout the way of the carrier pigeon.
"The population in Lake Ontario was extirpated by 1960. A combination of things led to an overall decline until toxicity kicked in, then all the other factors made no difference. After 1940, native lake trout were doomed."
Dr. Cook, research chemist for the Mid-continent Ecology Division of the National Health and Environmental Effects Research Laboratory, working with Dr. Richard Peterson of the University of Wisconsin, is investigating the role of toxic chemicals in the demise of Lake Ontario native trout. Core samples from the bottom of the lake revealed a long history of increasing amounts of dioxins, PCBs, and other POPs. In the laboratory, Peterson discovered that all lake trout hatchlings die in otherwise perfect conditions in the presence of just 20 parts per trillion of the dioxin TCDD (tetrachlorodibenzo-"p"-dioxin). "We don't know why lakers are more susceptible to TCDD than other species, but they are," Cook said. "The bull trout was the only fish more sensitive than lake trout to TCDD."
The genetic traits fine-tuned by centuries of natural selection to make a trout right for Erie, Michigan, and Ontario were scheduled for extinction by factors that nobody understood in 1940. Cook and Peterson look to publish a paper in the journal of the American Chemical Society detailing how it happened. "Sub-lethal effects of TCDD — things like malformation, impaired physiological function, neurological damage, and other problems that severely compromise survivability — begin at 4 or 5 parts per trillion for lake trout," Cook said.
To get some idea of how miniscule 5 parts per trillion is, expand the molecules in question to the size of softballs. About 3.5 trillion softballs would be required to cover the surface of Lake Superior. If black softballs represent molecules of TCDD, a concentration of 5 parts per trillion equates to 18 black softballs in a sea of white balls 500 miles long and 200 miles wide.
Concentrations that small begin causing serious birth defects in lake trout. Concentrations of 20 parts per trillion, or about 70 black softballs spread across Lake Superior, kills every hatchling lake trout in the system. Apparently, that's how virulent TCDD is to lakers. The bad news is that all the Great Lakes periodically contained levels of TCDD over 20 parts per trillion for decades.
Other studies have linked more than a half dozen other chemicals with mortality and reproductive failure among Great Lakes lake trout populations, most notably DDT, PCBs, polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). Because POPs are, by definition, persistent, meaning the molecules basically refuse to break down, rates of decline are extremely slow.
The good news (finally) is that dioxins, PCBs, DDT and many other POPs were outlawed in the 1970s. "With core samples, we reconstructed the exposure levels that took place," Cook explained. "The peak (for TCDD influx) was around 1968, and about 1970 for most PCBs. Sediment core analysis reveals significant improvement since that time. Evidence of lake trout reproduction has been appearing sporadically since the middle 1980s. We're now in the process of trying to determine if natural reproduction can, once again, supplant stocking in some areas of the lower (Great) lakes."
Meanwhile, POPs developed throughout the 20th Century will stay in circulation. "Research shows that PCBs persist in the atmosphere and are slowly making their way to the Arctic," said Dr. Cook. "Hot spots of contamination — old chemical manufacturing sites, paper mills — continue to release these chemicals over time. Levels are coming down, but I'm sure discharges from industrial sources continue. And, unfortunately, these chemicals may still be in production in other parts of the world."
For those interested in restoring Great Lakes lake trout populations, the biggest challenge will be to repel ongoing attacks on the Clean Water Act (CWA) and toxic cleanup strategies. Industrialists have big pockets and continue to fund drives to cripple the CWA. Hopefully, the Great Lakes will prove to be bigger and more important in the minds of voters.
Superior Success Story
According Michael to Hansen and associates, three distinct strains persist in Lake Superior: the "offshore lean" lake trout (similar to those that inhabit most deep, cold lakes in Canada), and the "humper" and "siscowet" forms that differentiated within Lake Superior after the pleistocene era. Indigenous only to Lake Superior, the siscowet is believed to spawn at depths of 150 feet, making it one of the deepest known spawners in freshwater. They live so deep, in fact, that it becomes impractical to either fish for them or study them most of the year.
Jeff Gunderson, associate director of Minnesota Sea Grant, had this to say about siscowets: "They are way more abundant than lean lake trout in Lake Superior — and we're wondering, is it something new, or has it always been that way? It's still somewhat of a mystery when and where they spawn. They're living down at 40°F, year-round, but they do come up to forage in shallower habitats, at times competing with lean lake trout.
"Population surveys of siscowets held in the Michigan waters of Lake Superior produced fascinating results. Nets were placed every 100 feet, down to 600 feet. At each 100-foot drop in depth, the siscowet catch increased down to 600 feet, the practical limit of setting and retrieving nets. Does the population continue to increase, right down to the bottom of Superior? Nobody knows."
But we do know that siscowets grow huge. That 61-pound laker landed on the Michigan side several years ago was determined to be a siscowet. Added layers of fat required to survive in the extreme depths of Superior give the siscowet a deep belly and stout appearance. Besides immense size, what makes the siscowet so rare is the lack of attention it receives. Though lake trout are popular gamefish in the North, Lake Superior's most populous form of the species exists in almost virgin condition, largely untouched and unspoiled by anglers or commercial operations. The aversion? With that high fat content, a big one will burn your grill to the ground, then horrify your taste buds.
In March of 2002, the Minnesota DNR announced that lake trout stocking within the management zone MN'‘3 (the northernmost of three management zones within Minnesota) would no longer be necessary because of recoveries in natural reproduction. The DNR cited fisheries management techniques, notably strict limits on commercial and sport harvest, along with improvements in water quality and better control of sea lamprey. (But another viable reason could be that Lake Superior volatilizes more PCBs through wave action than it gains through precipitation.) Zones MN-1 and MN-2 continue to require stocking to maintain population levels — but not much.
To say this is positive news in the world of lake trout management is an understatement of a magnitude that can be appreciated only by Great Lakes fishery biologists.
"It's one of the greatest fishery success stories ever," Don Schreiner, area fishery supervisor for MDNR lake Superior says. "Throughout most of Lake Superior, few areas remain where hatchery trout are needed. We're now trying to introduce Lake Superior strains into the other lakes. Strains deemed most adaptable to the habitat in Lake Michigan have been stocked on some of the deeper offshore reefs. Stocking, combined with sea lamprey control, has opened the door for restoration.
"Unfortunately, we still have no successful wild reproduction to report in Lake Michigan. Georgian Bay, however, shows some strong wild reproduction. Lakes Erie and Ontario have some natural reproduction, but few trout are living to adult size. Toxic pollutants and cannibalism by stocked fish are two possible obstacles, but the Great Lakes have been invaded by dozens of other exotic species. Two of the most damaging for lake trout have been alewives and smelt. These 'baitfish' are predators, easily capable of wiping out year classes of tiny hatchling lake trout."
Heroes of Restoration
Recent success stories in the other Great Lakes are many, but mostly of a put-and-take nature. Catching a lake trout over 20 pounds anywhere in the Great Lakes is easier right now perhaps than at any point in the past 50 years. But most are stocks from other parts of the continent that have been largely unsuccessful at reproducing. Yet charter captains like John Oravec of Lake Ontario view the restoration, to this point, as epic.
"I doubt that more time, effort, or money ever has been spent on the restoration of any other freshwater gamefish," Oravec said. "The restoration is ongoing and has been an heroic effort. There's a persistent, well-funded stocking program. Effort and funding for lamprey removal has been ongoing in all states and provinces surrounding the Great Lakes. Management study and effort has been immense, and it's working.
"Also, we're keeping lake trout alive until they get huge to give them an opportunity to eventually reproduce. They're the only salmonid in the Great Lakes protected by seasons and slot limits. The possession limit is 3 per person per day, and the slot limit only allows harvest of trout under 25 inches with one over 30 inches.
"The result of these efforts is that the size profile of lake trout is increasing," Oravec continued. "Ten years ago, a 12-pounder took braggin' rights. Now a 20-pounder is met with a ho-hum. One 11-year-old laker caught during the 1990s on the Bar weighed 39 pounds. Two winters ago, we caught and released lots of 18- to 25-pound lakers. Last year, the biggest fish in the LOC Spring Derby was a laker — 28.8 pounds — bigger than the biggest king salmon for the first time in the long history of the tournament.
"Studies by the NYDEC have shown that lakers are very releasable — they can survive being handled and released. We catch lots of lakers that show evidence of having been caught before, giving the lie to those who claim lakers die after being pulled from the depths. Release mortality is low."
Lake trout have a duct that allows them to release gas as it expands in the air bladder, unlike walleyes or bass. And the fishing, Oravec claims, is spectacular. "Doubles, triples, it's a riot. There's a prowling, mauling slurry of lakers out there. Lake trout are aggressive. I'll get 2 or 3 guys in the back of the boat just hauling until their arms fall off. Consumption advisories are dropping off, and lots of clients are keeping a few small lakers to eat. Lake trout, I understand, have more omega-3 triglycerides than any fish except bluefin tuna and king salmon," Oravec added. "Those are the oils that nutritionists say are so critical in maintaining a healthy heart."
Healthiest for some hearts is knowing salvelinus namaycush stands a fighting chance of thriving again in waters it inhabited long before homo sapiens sapiens arrived.