Ocean Watch

Monday, July 22, 1996

Visit to Lake Michigan yields
a good fish tale

RECENTLY, I made an unexpected trip to Wisconsin. I wasn't there two days before I began suffering ocean withdrawal. My skin flaked. My eyes dulled. I missed the sound of surf and the smell of salt air.

"Go visit Lake Michigan," a family member advised. "It's kind of like the ocean."

Yeah, sure, I thought. However, even if I couldn't get a marine fix, the idea of getting outdoors was appealing. I headed for The Lake.

As soon as I pulled into the parking lot of the harbor, my dehydrated cells perked up. This was salt air if I ever smelled it.

I know. Lake Michigan is fresh water. But honestly, although the temperature was cooler, the air smelled amazingly like the ocean.

I found the answer to this puzzle when I began walking to the lighthouse. On the rocks, and in the surrounding water, were bodies of countless small white fish. Apparently, the odor most of us associate with the ocean is fish.

Those 8- to 10-inch white fish lay dead and dying everywhere, many still twitching. I asked three groups of fishermen about these fish. All agreed that they were called alewives, but each had a different explanation for why they were dying:

• These saltwater fish migrate from the Atlantic up the St. Lawrence Seaway in springtime, then die when trapped in fresh water.

• Alewives are cold-water fish that die each year at this time when the water warms up.

• These fish die each year after spawning, like salmon.

Each explanation seemed reasonable and it turns out that each has its own partial truth. The Lake Michigan alewife story, a park ranger explained later, has an interesting biological history.

Once the lake contained 180 species of fish. Sturgeon, lake trout, herring and pike were among these, thriving in the lake and boiling the bays and shallows with spawning activity in springtime.

Then Europeans arrived and began settling the Lake Michigan region. An enormous logging industry arose and soon, logs and sediment choked every stream, river and bay of the lake. Along with the logging boom came towns. Sewage, industrial wastes and agricultural runoff soon followed. By the early 1900s, algae blooms from the added nutrients had destroyed the lake fishes' spawning grounds. Native fish populations crashed.

ENTER a few alien species. Carp, brought to ponds for food, escaped into the lake and multiplied. Later, eel-like sea lampreys wiggled their way into the lake through the seaway and took hold, munching on lake trout. By the late 1940s, lampreys were destroying 5 million pounds of lake trout annually, drastically dropping the population.

The scene was set for an invasion of alewives, relatives of herring, which found their way into Lake Michigan from the Atlantic Ocean in 1949. With the decimation of lake trout, the alewives had few predators. By the mid-1960s, alewives made up 90 percent of the lake's fish by weight, eating zooplankton that ate algae.

THE place, blooming with algae and alewives, was a mess. Water quality was awful. The alewife population peaked in 1966-67, leaving a spring shoreline littered with dead and decaying fish 3 feet high and 20 feet wide. Bulldozers were needed to clear beaches.

The lake began changing in 1972 with the Clean Water Act. Discharges were reduced, a lampricide was discovered, and salmon and trout were introduced to eat the alewives.

Alewives still thrive in the lake today, but in smaller numbers. These adaptable fish, which can survive in either fresh or salt water, spawn in spring in the shallows, where warm water currents from runoff kill the fish each year.

I enjoyed my day at the lake, but nothing can replace Hawaii's ocean. I can't wait to get home.