Lake Huron alewife population crashes


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Nov 18, 2002
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Lake Huron alewife population crashes

By Bill Parker
Presque Isle, Mich. — The sudden erratic movement of the planer board gave more of an indication of a strike than the traditional screaming drag of a reel releasing line. At times during the brief battle it felt like the fish had thrown the hook, but when the business end of the line came to the surface, so did a 20-inch chinook salmon.
It was a good day on the water, with three kings, an 8-pound steelhead, and a couple of undersized lakers coming to the net. But of the three kings, the largest was a 10-pounder. The other two were around two or three pounds each.
Similar scenarios are playing out this summer across Lake Huron as salmon fishing has been less than average. Anglers are catching fish, and sometimes limits, but overall the catch rate and the size of the fish both are down.
Biologists have noticed the decline, especially in the size of the salmon. The apparent culprit is a drastic decline over the past two years in the number of alewives in Lake Huron.
“A study by the USGS (U.S. Geological Survey) showed small year-classes of alewives for two years in a row,” said Jim Baker, the DNR’s fisheries unit manager for the Southern Lake Huron Management Unit. “They’re not making it through the winter.”
Salmon were introduced into the Great Lakes in the 1960s as a way of controlling an alewife population that was growing unchecked. Prior to that introduction, many areas of Great Lakes shoreline annually were littered with dead, rotting alewives.
One of the many invasive species that now resides in the Great Lakes, the alewife is the primary and favored food source of salmon, although salmon also eat smelt and other species of forage fish.
“Salmon are extremely dependent on alewives for forage,” Baker said. “Lake trout, on the other hand, will eat anything.”
Jeff Schaeffer, a research fisheries biologist with the USGS Great Lakes Science Center, has been studying the predator/prey relationships in the Great Lakes fishery.
“What we’ve seen over the past two years is a very sharp decline in alewives,” Schaeffer told Michigan Outdoor News. “Overall, the evidence suggests it’s a combination of severe winters and heavy salmonid predation.”
Michigan has experienced back-to-back hard winters. While ice cover and cold temperatures bode well for Great Lakes water levels, the same doesn’t hold true for some forage fish.
“Alewives are born in the summer and we sample the populations in the fall,” Schaeffer said. “When we’ve sampled them again in the spring most of the young of the year have been gone. The numbers are low and the smallest individuals are the ones that are disappearing. Now, we’ve gone for two years without an influx of young-of-the-year fish into the population so the number of older fish is down as well.”
The reason for the die-off of the young fish remains a mystery.
“It could be the cold. It could be that they are forced into deeper water where there is less food. At this point we’re not sure,” Schaeffer said. “Some other theories that are being looked into are that ice cover may play a role, or that storm severity may play a role.”
Studies by the GLSC have shown that the overall forage base for salmonid in Lake Huron last spring was down 83 percent from the five-year average.
“My guess is that as the alewives declined, the salmon and lake trout turned to smelt, but smelt have been declining steadily for almost 20 years,” Schaeffer said.
With the loss of two year-classes of young-of-the-year alewives, salmon and trout are eating more of the older fish. And studies have shown that there are more salmon and trout eating them than many fisheries managers once thought.
“What we’ve seen in recent years is that there are a lot of wild chinook out there,” Schaeffer said. “Marking studies have been conducted and most of the (hatchery) fish are marked or tagged. What we’ve found is that anglers are catching a lot of unmarked fish, so we know there are a lot of wild fish out there. I think it’s safe to say that the chinook population has increased and that the lake trout population is increasing”
Although the alewife population is in decline, Schaeffer said it could turn itself around. Alewives are very prolific.
“Last year, after the first hard winter, alewives bounced back tremendously,” Schaeffer said. “We had a huge year-class in 2003, one of the largest we’ve seen in Lake Huron. Unfortunately, from a salmon’s perspective, that year-class didn’t survive the winter very well.”
Schaeffer said that at this point no management decisions have been made regarding alewives and salmon in the Great Lakes.
“But it’s something we need to start talking about,” he said.
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