Lakers bounce back on Huron
Written by Detroit Free Press   
Thursday, 12 May 2005 11:54
As the research boat Chinook rocked and rolled on a three-foot sea, Kenny Glomski's sharp knife sliced open the belly of a lake trout, exposing a cavity covered with a rubbery layer of almond-colored fat.

"Wow, look at that," said biologist Jim Johnson, leaning in to make a digital picture of the laker's interior. "That's a very healthy fish. We haven't seen fat like that in them for a long time."

Johnson picked up a smaller fish that had been in the lake trout's belly. It was a smelt, a bait fish that had almost disappeared from the stomachs of lake trout and other game fish in the past few years.

Ken Deaton, a Harbor Beach charter captain spending the day on the Chinook, confirmed what Johnson had been hearing from other anglers since last year.

"The smelt are coming back," Deaton said. "Last weekend, I cleaned a couple of lake trout that had two handfuls of smelt in their bellies when you opened them. It's been a long time since we've seen that."

Once again, Lake Huron is undergoing a sea change. Lake trout are making a comeback while salmon are declining in the world's fourth-largest body of fresh water.

Though some anglers complain that the changes have drastically reduced the numbers and sizes of the chinook and coho salmon they prefer to catch, others are pleased that the decline in salmon has resulted in more native lake trout. Anglers in the Thumb area took a record 40,000 lakers last summer.

"Last Saturday, we had a trip where we caught two cohos, three chinooks and five lake trout," said Deaton, who runs the charter boat J-Lyn with his wife, Janice. "I think it's a lot more fun to get a mixture like that.

"We spoiled the fishermen in Michigan. Salmon fishing was so good here that people thought they were being cheated if they didn't get a limit every time they went out."

Pollution, overfishing and, most significantly, the accidental introduction of parasitic sea lampreys virtually wiped out lake trout in Lake Huron by the 1960s. Tiny populations hung on in Georgian Bay on the Canadian side, although biologists didn't know that then.

With no predator to control them, two exotic species from the Atlantic Ocean -- alewives and smelt -- exploded in numbers. Then the arrival of zebra mussels in the 1980s gave the alewives an edge over the smelt.

When salmon were introduced almost 40 years ago to try to bring the lakes back into some semblance of ecological balance, they found a smorgasbord of bait fish awaiting them. Pacific salmon fishing in the Great Lakes soon was among the best in the world and far better than in most of the native waters from which the salmon came.

Government agencies and Indian tribes could control factors like the number of salmon they put into the lakes, but they couldn't control other factors, like the arrival of other exotic species. Salmon also could reproduce naturally in numbers far exceeding the fish coming from hatcheries.

About five years ago, biologists figured there were about 10 pounds of alewives for each of Lake Huron's 14.7 million acres of surface area. Alewives -- a kind of bait fish -- averaged 10 to the pound, so it meant about 1.47 billion were roaming the second biggest of the Great Lakes.

But how many were eaten by the salmon introduced in the 1960s to reduce out-of-control numbers of alewives and smelt?

"All of them," said Johnson, who heads the state Department of Natural Resources' fisheries research laboratory at Alpena. "The salmon were eating the alewives faster than the alewives could reproduce, so when you had a couple of bad years of alewife reproduction, like we had in the last couple of years, and you brought in things like the mussels that competed for food with alewife fry, they just disappeared."

Zebra and quagga mussels also appear to be culprits in the disappearance of a tiny freshwater shrimp called diporeia, which can't compete with untold billions of mussels that filter much of the available food out of the water. The exotic mussels have helped make the lake water remarkably clear, but they have had a dramatic impact on the populations of whitefish and lake herring that fed largely on diporeia.

"We used to be able to age whitefish by counting growth rings on the scales, like counting the annual growth rings on trees," said Johnson, whose grandfather was a commercial fisherman for lake trout and whitefish out of Port Sanilac. "But the whitefish have just stopped growing, so we can't do that anymore."

Now the DNR dissects otoliths, or ear stones, from the heads of whitefish and sends them to a laboratory to determine their age. In the otoliths, fish "keep adding growth rings even if the scales stop," Johnson said. "We were stunned to find that a 15-inch whitefish might be 15 years old."

On this day Johnson, crewman Glomski, technician Steve DeWitt, statistical biologist Ji Xiang He and summer worker Abe Bruski, all from Alpena, were pulling four nets they had set in Lake Huron in an effort to see how the lake trout were doing. Each net was 900 feet long.

During the winter, DeWitt and Glomski work on boat maintenance and repairing and rebuilding five miles of gill nets they set in the summer at various spots from Harbor Beach to the Straits of Mackinac.

The lake trout in Huron are not only smaller than they used to be, many are maturing and reproducing earlier, at 3-4 years rather than 5-6, something Johnson said is a sign of a population under stress. The lack of bigger prey fish like whitefish is a primary reason the Great Lakes rarely produce the 20- to 40-pound lake trout they did before the lake trout population crashed.

"The rule of thumb is that the prey species needs to be a quarter to a third the size of the predator to provide good growth," Johnson said. "With five- to seven-inch alewives the primary prey species, once a predator gets to 22-24 inches, it just won't keep growing very fast. But a 15-inch lake herring is just perfect for a 45-inch lake trout."

 
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