The walleye run in the Detroit River this spring has been good, with lots of fish and happy anglers, and that's also true for the other major run in Ohio's Maumee River 35 miles to the southwest.
So why are biologists who manage Lake Erie's walleye population so worried about the future?
First, while the estimated Lake Erie walleye population of 26 million has been stable for the past couple of years, it's only about a third of what it was 25 years ago.
Second, despite a record walleye hatch in 2003 that is still the mainstay of the fishery, spring spawning success in the past decade has been weak, with one year's hatch failing almost completely.
Third, the expansion of low-oxygen zones caused by man-made loading of phosphates and other nutrients may drive walleyes out of large sections of Lake Erie and over time could reduce the numbers of walleye that spawn on shorelines and offshore reefs.
Michigan controls only 1% of Lake Erie, a mere 112 square miles out of nearly 10,000. Yet that 1% is at the heart of the western basin spawning area that supports huge sport and commercial fisheries.
Millions of walleyes move through the Detroit River each spring, some to spawn there, others going to or from Lakes Erie, St. Clair and Huron.
"We've had a fabulous spring," said Gerry Gostenik, a well-known bass guide who fishes walleyes in March and April until bass season opens. "It was weird in March when we were fishing in shorts and sandals. We're back to normal weather now, but the fishing is still good."
Paul Vanderbilt from Bowling Green, Ohio, and two friends were recently launching his 18-foot Lund at the Wyandotte Boat Ramp for the third straight day, "and we've had limits in the river (five fish each) every day. The first two days we caught over 20 each and kept fish from 3 to 6 pounds. They're hitting ball-head jigs with plastic tails. When we start, we each use a different color jig and tail to see if the fish have a preference."
"We have a lot of walleyes in Ohio in Lake Erie, but I like coming to the Detroit River because it's so well-protected. You can always find a place to fish out of the wind even when it blows hard," Vanderbilt said. "Fishing the Ohio shoreline, there are a lot of days you just can't get out safely in a boat this size."
Lake Erie sustained huge sport and commercial walleye fisheries through the mid-1950s, when industrial pollution and an alewife boom caused a major collapse. Mercury pollution was so bad by the early 1970s that states would sometimes order walleye fishing closed.
With the Clean Water Act of 1972, the fishery rebounded with improved water quality, decreasing alewife numbers and tighter controls on sport and commercial fishing.
Walleye numbers peaked at 70 million by the late 1980s. Then the fishery was hit by a triple threat -- overharvesting, more invasive species including zebra mussels and spiny water fleas and round gobies, and several years where spring spawning success was effectively nonexistent.
At its peak, Lake Erie boasted 7,000 walleyes per square mile, but the Michigan Department of Natural Resources said a dozen years later that figure had dropped to 1,700. That meant the walleye population had dropped nearly 80% to 16-million fish.
Increased controls on the fishery have helped bring the population back to about 2,500 per square mile today.
While there was a bumper walleye hatch in 2003, most years since have been dismal. Fisheries scientists don't know if this is the result of environmental causes created by man, or part of a long-term natural cycle, or both.
Whatever the cause, they do know that the continued buildup of phosphates and other nutrients in recent years has reached levels not seen since the early 1970s and has exacerbated the problem.
Now Ohio and Michigan have agreed to stop squabbling over who is more at fault and try to remediate the major causes -- sewage overflows from Detroit and runoff from Ohio farms.
Mike Thomas is a Michigan DNR fisheries biologist who grew up in Taylor and for 20 years has conducted research surveys on Lakes St. Clair and Erie.
"Walleye recruitment has probably always been highly variable, but in recent years we seem to have seen more weak classes than good ones," he said. "We're seeing something similar with yellow perch in the western basin, where their numbers are down while in the central basin they're increasing."
Thomas said that the 26-milllion walleye estimate for 2012 is up slightly from the 24 million in 2011. But most big fish are from the record 2003 hatch, when sampling produced an average of 183 young-of-the year fish per trawl.
Since then, the fall sampling has produced YOY numbers ranging from a high of 26 per trawl in 2010 to near zero in a couple of years.
The U.S. Environmental Protection Agency's Lakes and Large Rivers Research Branch has studied Lake Erie extensively and found walleye numbers can vary wildly over time.
Biologists worry that the trend has been mostly downward for 15 years, and the adult walleye estimate dropped below 20 million in 1997, 2000, 2002 and 2004.
Todd Kalish, a DNR biologist who serves as Michigan's Lake Erie basin coordinator, said: "The most important factor in determining the success of walleye spawning is the weather."
While a cold spring seems to be beneficial, high winds and floods can sweep eggs away and wipe out an entire year class.
Kalish also is concerned about Lake Erie's algae blooms, saying that "it's creating an environment that's good for fish like bass and sunfish, but those conditions usually are poor conditions for walleyes and perch."
"We don't know if that's affecting the walleye spawning habitat yet, but last year we saw the highest spikes yet for algae concentrations. We're concerned that the young of the year may be vulnerable," he said.
More Details: Walleye limits
The Great Lakes Fishery Commission has set the 2012 total allowable catch (TAC) of walleyes on Lake Erie at 3,487,000 fish out of a total population estimated at about 26 million with anglers in Michigan waters allocated 203,000.
Anglers will be allowed six walleyes per day on the state's Lake Erie waters. The daily possession limit is based on the state's allowable share of the walleye TAC.
The Michigan Department of Natural Resources sets the limit according to the following table:
|If Michigan's share of the annual TAC is ...||then the daily possession limit for walleye shall be|
|Greater than 108,364||Six|
|96,958 to 108,364||Five|
|85,551 to 96,957||Four|
|74,144 to 85,550||Three|
|62,737 to 74,143||Two|
|Less than 62,737||One|