Feb 9th 2012
Good, 
and bad 
news on lampreysTests of chemical signals called pheromones prove they can trick sea lampreys to avoid streams that offer good spawning habitat and lure them to streams where baby lampreys won't survive.
"It's hard to see any good news when it comes to invasive species, but the sea lamprey is one case where we're winning the battle," Dr. Marc Gaden said this week during a briefing on new lamprey control efforts by the Great Lakes Fishery Commission and other agencies.
That's the good news. 
The not-so-good news, at least in the short run, is what the scientists learned when they tried a full-count press on the handful of rivers and creeks that were thought to produce most of the lampreys in Lake Erie.
While sea lamprey numbers have been reduced by 90% in the four other Great Lakes, they remain stubbornly high in Erie, where scientists thought nine or 10 streams accounted for nearly all the spawning.
"We thought that if we hit all of nine or 10 at once for two years, we'd eliminate most of the lampreys and that they might not come back to a couple of them," said Dr. Michael Siefkes, the fishery commission's sea lamprey expert.
But the result was a much smaller reduction than expected in the voracious, eel-like creatures, leading scientists to conclude there must be other lamprey nursery streams that have been overlooked.
One might be the St. Clair River-Detroit River corridor between Lake Huron and Lake Erie, which couldn't support lamprey spawning until water cleanup programs eliminated most pollution, Siefkes said Tuesday during a briefing on the lamprey control work.
Sea lampreys entered Lake Ontario in the 1800s, reached Lake Erie by 1920 and were found in Lake Superior in 1939. Unlike common eels, which are bony fish like perch and bass, lampreys are more primitive survivors from the earliest age of fishes.
They lack jaws and a bony skeleton, but have a sucker mouth filled with rings of hooked teeth that clamp onto fish ranging from salmon to perch, and they use a tongue like a file to bore into fish and live off their blood and body fluids.
Lampreys live for a year as parasitic adults in the Great Lakes, then swim upstream where they die after laying eggs that hatch into worm-like larvae. Larvae live under the mud for three or four years before heading downstream to the big lakes.
Studies show that lampreys can detect pheromones given off by the larvae that indicate a stream is a good place to lay eggs. They also can detect other pheromones given off by dying larvae and rotting lamprey flesh, which signals that a stream is a poor place to lay eggs, or perhaps that earlier arrivals already have used up the spawning habitat.
Siefkes said that while the way they work isn't yet fully understood, tests have shown the two classes of pheromones can be used to fool lampreys into avoiding streams that have good spawning habitat and draw them into rivers where the survival of their larvae is poor, which he called the "push-pull" technique.
In smaller streams, the attracting pheromone can be used to lure adults into traps and kill them before they can spawn.
The pheromones offer promise for reducing lamprey number in big rivers that are difficult and expensive to treat with chemicals that kill the larvae, like the St. Marys River near Sault Ste. Marie.
The bad news on lampreys 
Lampreys were a primary cause of the near-disappearance of lake trout from the Great Lakes and disruption of the lakes' ecosystem, and they continue to kill millions of pounds of valuable sport and food fish.
Gaden said lamprey reduction has played a role in the resurgence of lake trout in Lake Huron, where the numbers of naturally spawned fish has risen from about 3.5% 20 years ago to 33% today.
He called the sea lamprey "the most devastating predator to enter the Great Lakes," but he should have added "to date." The Asian carp knocking on the door of Lake Michigan at the Chicago Sanitary and Ship Canal are plankton eaters that affect native fish in different ways than parasitic predators like sea lampreys, but the effect could be even more devastating.
The work with pheromones offers a promising avenue of research for controlling the spawning of any anadromous fish -- species that live in the ocean or a large lake and ascend rivers to spawn. That includes the two most harmful species of Asian carp.
Wildlife agencies complain about lack of funding. Maybe it's time the Great Lakes states stopped wasting money planting salmon in the lakes don't need and fund more research that could make our fish stocks self-sustaining
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Topic: Good, bad news on lampreys (Read 1421 times)
