By the Detroit Free Press
---- — The summer of 2012 may go into the record books for several reasons (heat, drought, lack of cherries), but Michiganders should also take note of potential pivot points in the health of the Great Lakes.
The exemplar this year is Lake Michigan, where signs of stress are building.
First is the decision among the states that oversee the Lake Michigan fishery to cut back on the amount of chinook salmon they put into the lake each year. This has happened twice in the past, but 2012 marks the biggest cutback. It is an emphatic response to disruptions in the food web that have led to fewer alewives and less food for bigger fish further along in the food chain.
Those who go out sport fishing may not be catching fewer fish right now, but fish have gotten smaller as prey fish dwindle. And chinook salmon, considered the fastest growers and biggest eaters in the lake, are an obvious species for cutbacks to maintain balance.
The stocking reduction is not particularly controversial in Michigan, where the salmon spawn quite well on their own, and Michigan is taking the biggest cutback in stocking without much complaint. In Wisconsin, however, anglers have protested because fewer fish released means a lower return to rivers there.
But as long as invasive species — in this case the culprit is most likely the quagga mussel — keep changing the balance of food supplies in the lakes, fisheries experts will have to keep adapting. The health of the entire fish population matters most in the long haul, and that involves more than just the chinooks. There are Atlantic salmon in the lakes, too, along with steelhead, brown trout and lake trout.
Invasive mussels also may be the root cause of algae showing up along the Lake Michigan shore in places like Sleeping Bear National Lakeshore. The presence of algae is another sign of imbalance, in this case because the mussels filter the water as they eat, which clarifies the water; clearer water in turn allows more plant growth.
Is it any wonder that Michiganders go bonkers at the idea of Asian carp getting into the lakes, when invaders as small as zebra and quagga mussels keep causing so much trouble? Many problems that mar the Great Lakes can be remedied over time, but foreign species — sometimes more aptly called biological pollution — will hang around forever.
That's why efforts to close off the routes of entry, from ballast water to interconnected waterways, still rank first among the battles defenders of the Great Lakes have to keep fighting.
-- Detroit Free Press