BY ERIC SHARP • FREE PRESS OUTDOORS WRITER • May 15, 2008
Last summer, Lake Michigan anglers caught salmon in near-record numbers, so many that next year state fisheries scientists want to increase the daily chinook and coho limit to five from the present level of three.
Unfortunately, that's not because the lake's salmon are doing so well. Randall Claramunt, a Department of Natural Resources research biologist, said chinook salmon numbers in Lake Michigan continued to decline in 2007, and so did the average size of the fish.
And even more worrying, although there was a modest increase in the alewife population, overall prey fish numbers dropped to record low levels.
Despite the huge numbers of salmon that were caught last summer, the total Lake Michigan salmon take by weight of 17 million pounds was less than half of the average weight from 1954 to 1985 and a third of the 56 million pounds landed in the peak year of 1985.
The increased salmon bag limit in 2009 would be aimed at staving off the kind of collapse of the fishery that occurred in Lake Huron three years ago.
"Going to five chinooks from three will kill about 25,000 more chinooks a year," Claramunt said. "That might not seem like much in a lake-wide population of 10 million salmon, but it can make a difference in the number of alewives that survive."
Alewives, like salmon, are an exotic species in the Great Lakes, but the alewives swam in on their own from the Atlantic Ocean in the 1930s. Over the next 30 years they multiplied to such excessive levels that salmon were introduced to the Great Lakes in the 1960s to control their numbers.
The irony today is that this former scourge has become crucial to the survival of the salmon fishing industry that has grown up in the lakes in the last 40 years, and biologists worry that there aren't enough of these one-time exotic nuisances to support the chinook stocks.
Another exotic that arrived about 20 years after salmon is believed to be responsible for the salmon fishery collapse in Lake Huron. Zebra mussels, and later the larger quagga mussels, have removed so many nutrients from the waters of that lake that the food chain apparently has collapsed at its base.
The mussels apparently have starved out alewives, and although this has resulted in increased numbers of other prey species like emerald shiners and smelt, those fish won't support a large salmon fishery.
"An alewife is like a swimming cheeseburger, and a smelt is like a swimming lean steak," said Jeffrey Schaeffer, a research scientist at the U.S. Geological Survey Great Lakes Science Center in Ann Arbor. "Chinook salmon grow faster and bigger on a diet of alewives. And in Lake Huron, we hardly see alewives any more in places where we once saw huge numbers of them."
There are some hopeful signs. The 2005 hatch of alewives in Lake Michigan was one of the biggest recorded, and the alewives seem to be surviving and growing better than in previous years. But Claramunt said that's probably because the number of salmon feeding on the alewives is down.
"It's a fascinating time" to be a research scientist on the Great Lakes, Schaeffer said, "especially when you can contrast and compare what's going on in Lake Huron and Lake Michigan." He said that anglers should be aware that more and better research is being done today by more scientists than at any time in the past.
"We're seeing some good things as well as bad," Schaeffer said. "We've seen that when the alewives disappear, the natural reproduction of walleyes and perch increases dramatically. And native prey species like emerald shiners are coming back."
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