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Field & Street



If you doubt that life is a crapshoot, consider the fates of the spot-tailed and emerald shiners in Lake Michigan. They are both minnows, members of the genus Notropis, the largest genus of freshwater fish in North America. They both feed on aquatic insects and small crustacea. The largest spot-tailed shiners are six inches long. Emerald shiners are even smaller.

Both of these fish were common in the lake in the past. Emerald shiners could even be classed as abundant. In favored places they would be so thick in the water that it seemed you could stand on them and not sink.

Spot-tailed shiners are still common, but the emerald shiner has become rare in recent years. Why? It all has to do with their eggs. Both species cast their eggs in the water, but the eggs of spot-tailed shiners sink to the bottom. The eggs of emerald shiners drift in the water--below the surface, but well above the bottom.

In old Lake Michigan the emerald shiner's habits worked perfectly well. The eggs drifted with the currents and hatched when they were ready to hatch.

But then some changes occurred. First smelt and then alewives entered the lake. Both of these fish feed in the open water, eating tiny plankton--and the drifting eggs of minnows--well above the bottom. Suddenly the habits that had served the emerald shiner for thousands of years were no longer adaptive.

With its ability to reproduce drastically curtailed, the emerald shiner started a downward slide that still continues.

I learned about the emerald shiner from Allen Feldman, my principal consultant on matters ichthyological. Allen used to run the Great Lakes exhibits at the Shedd Aquarium, and he recently spoke at a meeting of the Lake Michigan Federation on the changes that have occurred in our fish since Europeans began to settle here.

His talk made me realize the similarities between the lake and our local prairies. Both have been stripped of native species and are now dominated by aliens. Both support far fewer species than they once did.

His talk also made me realize anew the grotesque absurdity of the argument over jobs versus the environment. The Great Lakes are yet another demonstration of the fact that environmental protection is not an optional expense. We can delay payment, but the longer we delay the bigger the bill becomes. Cleaning up is always more expensive than prevention, and it often doesn't work as well. Sometimes it doesn't work at all.

Fish began to migrate into the newly formed Great Lakes as soon as the glaciers that created them receded. Coregonids--whitefish, chubs, ciscos, lake herring--came from the Pacific Northwest. Bowfins, long-nosed gar, grass pickerel, arid suckers came from southern rivers--the Mississippi and its tributaries. Green sunfish, pumpkinseeds, and bluegills came from the south and east. About 180 species of fish lived in these lakes when Europeans began to settle on their shores.

The cold water of the lakes served as a barrier for some species, but there was enough variety in the available habitat to create variety in the fish populations. Fish such as walleyes and northern pike lived in quieter waters and in bays where aquatic vegetation grew thickly. Yellow perch and rock bass liked bays or near-shore areas with less vegetation.

Out in the cold, deep water of the open lakes, the lake trout was the dominant large predator. This fish lived its entire life in the open waters, even spawning there. The tribe of coregonids provided food for the lake trout.

In the shallow waters the bottom feeders included the lake sturgeon, perhaps the largest freshwater fish in North America. The record catch for the Great Lakes was a fish pulled out of Lake Superior in 1922 that was just an inch short of eight feet long.

Other bottom feeders included the various species of suckers. Both suckers and sturgeon are fish of clean bottoms. They like sand and gravel rather than muds.

The destruction of the native ecosystems of the Great Lakes began in the 1830s, when fishermen settled in villages on the upper lakes--Huron, Superior, and Michigan--and began harvesting whitefish and lake herring. They cleaned and salted the fish and packed them in barrels for shipment to the east. These species began to show serious declines within a few decades.

Fishermen regarded the sturgeon as a trash fish that tangled nets and ate the eggs of other fish. They killed sturgeon whenever they could, piled their bodies on the beach, doused them with kerosene, and burned them. Later a profitable market developed for sturgeon roe to make caviar. In 1880 Lake Michigan produced four million pounds of sturgeon, but catches declined after that. The sturgeon is now endangered in Lake Michigan.

The peak year for commercial fishing in the Great Lakes was 1899, when 147 million pounds of fish were pulled from the five lakes. This was not a sustainable yield. By the 1950s stocks of many commercially valuable fish were seriously depleted. At this point the sea lamprey entered the upper lakes.

Lampreys belong to a primitive order of vertebrates whose living members are all parasites. Their jawless mouths are suckers ringed with several rows of teeth. They live by attaching themselves to fish, sucking out large helpings of precious bodily fluids, and then dropping off.

Lampreys live in salt water as adults, but they come up rivers to spawn. Their larvae live for years buried in the bottom mud of streams before maturing and heading out to sea.

Lampreys entered the upper lakes through the Welland Canal, the waterway that allows vessels to get around Niagara Falls. In the ocean lampreys are no particular problem. They tend to go after very large fish, which can survive a temporary infestation. In the upper lakes they found no very large fish. Their feeding was a coup de grace for the lake trout, finishing the job the commercial fishermen started.

By the mid-60s the lake trout was functionally extinct in Lake Michigan. There were still a few fish around, but not enough to play their ecological role as top predator. At this point the alewife, another saltwater species that had come in through the Welland Canal, entered the picture. Most people are familiar with the alewife saga. With no predators to eat it, this small fish enjoyed a huge population explosion followed by catastrophic die-offs that littered the beaches of Lake Michigan with heaps of alewife corpses.

Exotic salmon were introduced to Lake Michigan to control the alewives. They did an excellent job of it, and as an unexpected bonus created a multibillion-dollar sport fishery.

So now we have a lake where the dominant predators are alien species that do not reproduce naturally. Their populations must be constantly augmented by fish raised in hatcheries. And eating them is a risky act because of the toxic chemicals they contain.

Commercial fishing continues in the Great Lakes. As many as 110 million pounds of fish are taken every year. But a large part of this impressive catch consists of alewives, which are ground up and used in animal feed.

And the cost of maintaining a degraded and reduced commercial fishery and a sport fishery that provides only marginally edible fish is very high. Illinois spends about $750,000 a year to raise salmon and trout in its hatchery. But that cost is tiny. Michigan spends $4 million on its hatcheries for the same purpose. Controlling the sea lamprey costs as much as $15 million a year. Zebra-mussel control runs $4-5 million a year, and this will probably go up in the future. And there is no guarantee that the control program will be successful.

In Duluth Harbor lives a European fish called the river ruff, which was accidentally released from ships that dump ballast water in the harbor. If this fish spreads through the lakes, it could destroy whitefish and yellow perch populations. Just doing the research on how we might deal with this menace will cost more than a million dollars, and it may not produce a workable control method.

Add to all this the millions spent by the EPA and other federal agencies to deal with such problems as persistent toxics, the chemicals that make our alien salmon unsafe to eat, and you have a very large pollution bill.

If we had treated the lakes with respect from the beginning. If we had not overfished them. If we had made serious efforts to keep alien species out. If we had not polluted the lakes. Then we could be pulling up to 100 million pounds of high-quality, high-protein food from the lakes every year. And the food would be almost free. The cost would be nothing more than the cost of sending boats out to catch it.

Instead we are spending millions to sustain a fishery that produces a mixture of animal feed and human food that is more dangerous than cigarettes. The cost of environmental degradation is higher than the cost of environmental protection.

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