Whoa, now. I just spent a couple of days with Lake Erie biologists who think they're beginning to like zebra mussels.
They say people blame those nefarious little clam-like animals for too much of the clarification of that lake. In fact, clarification began in the early 1980s when phosphorus dumping was phased out in all the Great Lakes. And, they point out, clear water really is not bad at all. It just makes the fishing trickier.
"It took a while for the phosphorus to work itself out of the system," said Dave Insley, an administrator of Ohio's fish hatchery section. "But zebra mussels get all the credit."
Or, in this case, the blame for changing the system. Since the mussels consume everything they can strain from the water, including suspended solids, they are accused of stealing food from every other critter. Some scientists believe the food chain is breaking.
Years of phosphorus from detergents and farm chemicals acted as a nutrient to produce algae and microscopic plant life in Erie and other Great Lakes. This helped cloud the water green. It was more full of life than dirty. Well, there's obviously much less life suspended in the Great Lakes now that phosphorus has diminished and zebra mussels have proliferated. Right here in Lake Michigan, where you once couldn't see your hand beneath your elbow, you now can watch fish swim 12 to 14 feet down.
Some of Ohio's fishery honchos are convinced these changes are positive. They cite hordes of walleye and smallmouth bass from huge hatches in 1990 and 1991. They see abundant gizzard shad and emerald shiner baitfish. While it is true that phytoplankton have diminished, they feel the food web for gamefish simply has been switched to the benthic area-in other words, to small fish that feed on the bottom, where things rot and mussels defecate, returning nutrients to the system.
According to Dick Pierce, head of Ohio's Division of Wildlife, there are other benefits to clarification. He thinks smallmouth bass nest in deeper areas that sunlight formerly could not penetrate.
"And ducks are feeding on those mussels," Pierce said. "We're seeing concentrations of divers and puddle ducks that we haven't seen on Lake Erie in years, and they're all eating mussels. Why, we had 200,000 scaup last fall off Toledo."
Pierce also expects clearer water and deeper weeds to spearhead a northern pike recovery, as well as better largemouth bassing in Erie's bays. If so, could the zebras be a harbinger of good in Lake Michigan? Well, despite the tail-wagging in Ohio, local scientists are in doubt.
Tom Trudeau, who manages the Illinois Department of Conservation's Great Lakes program, points out that Erie and Michigan are hardly the same as far as fish production is concerned. "Lake Erie's western basin (a fish factory now said to hold 70 million walleye) is more like Green Bay or Saginaw Bay than Lake Michigan," he observed. And if, indeed, the phytoplankton base is diminishing, he asks what then can happen to the tiny animals that depend upon it for food?
Ellen Marsden, an Illinois Sea Grant scientist who studies Lake Michigan, thinks small signs of serious change are appearing. She points to the mystery of Lake Michigan's four straight poor perch hatches. That's why so many jumbos are being caught. There aren't enough smaller, younger fish to average out the catches. And when those bigger, older fish are gone, where will the perch fishery be?
Marsden also notes the mysterious crash of salmon-feeding alewives in Lake Ontario last year. "Now, was that because the zebra mussels sucked up all the food from Lake Erie before it flowed into Ontario?" she wondered.
Marsden also raised a chilling possibility about all those ducks feeding on mussels, citing international studies that show zebra mussels tend to accumulate pollutants. Some mussels in Europe that became overloaded with cadmium apparently contributed to distorted duck embryos.
Equally concerned is Fred Snyder, Marsden's counterpart at Ohio Sea Grant. While he concedes that early predictions of disaster have not come true, Snyder points to several tell-tale signs of change.
He said new studies show ominous declines in zooplankton, the microscopic, minnow-feeding animals that eat those missing tiny plants. "And that's exactly what gizzard shad and emerald shiners eat," Snyder said.
He said last year saw a poor class of emerald and spotted shiners. He also said Lake Erie has not had a good walleye hatch in the last two years. Moreover, those abundant 1991 fish are not growing at the same rate as the big hatch from 1990.
"And while there's been no decrease in the size of shad in the western basin (where all those walleye thrive), the eastern and central basins have seen a decline in smelt, which also are forage for trout and salmon," Snyder said. "So there are a lot of little signals popping up."
Another barometer is catch rates. Snyder said anglers averaged 5.6 walleye per hour in the peak year of 1984. That rate declined steadily to a low of 1.4 in 1990, rising to 2.7 last year. "So even with two huge classes in 1990-91, the recovery has been modest," he said.
We sat in silence together. It makes you wonder, doesn't it?