Study: Carp likely to stay near shore in Lake Michigan

By Ralph Loos

Chicago —  Asian carp would have no  trouble finding a meal if they make it to Lake Michigan – but the fish are not likely to spread out across the big lake once they arrive, instead hanging near the shorelines where their food sources exist.

These crystal ball prognostications are provided by the U.S. Geological Survey, which recently took a hypothetical “not if but when” look at the invasive fish and Illinois’ connection to the Great Lakes.

To be exact, USGS researchers offer, “If invasive bighead carp and silver carp spread into Lake Michigan, there would be enough food available for these particular species to survive.”

No surprise, fisheries biologists and officials trying to keep the carp out, say.

Still, information provided by the USGS study is considered critical in helping mitigate effects of what many label as an “impending Asian carp invasion.”

Those studying the fish used predictive models to simulate fish growth and food consumption to determine the suitability of Lake Michigan and the other Great Lakes to Asian carp invasions. According to USGS, scientists used satellite imagery of Lake Michigan showing near-surface algae to determine how much food would be available for the carp. Green algae and blue-green algae, specifically floating algal blooms that can be seen on the surface, are a preferred food source for the fish.

“The water temperatures and algal concentrations detected in Lake Michigan from 2009-11 show that the bighead and silver carp populations could not only live in this environment, but continue to grow,” said Karl Anderson, lead author of the USGS study. “Most areas of the lake had insufficient algal food for bighead and silver carp, but the model indicates that nearshore areas and embayments had plenty of algal food to support survival and growth.”

The expectation that the carp would stick to Lake Michigan’s shorelines are yet another downer for fans and sportsmen of Lake Michigan. As witnessed up and down the Illinois River system, silver carp often react to human activity – boating, mostly – by jumping. The USGS notes that this activity is dangerous because silver carp often jump into boats, harming people and property.

“Concentration of silver carp near the coastline would enhance the propensity of such nuisance interactions with boaters,” the USGS study offered.

As for food, USGS scientists used models it developed to determine how much algae carps need to eat to survive.

“Food availability and water temperature are the greatest sources of uncertainty for predicting fish growth potential,” the agency pointed out. “Water temperature is a key factor in determining how much bighead and silver carp need to eat. “

Growing arsenal against invasives

As the look at Lake Michigan’s vulnerability to Asian carp continues, there are new methods and tools being developed to help fight off invasive species – be they fish, plants or … pigs.

For example, companies are now marketing traps for feral hogs that are triggered by cellphones.

“There’s enough activity that there’s starting to be an industry,” University of California, Santa Cruz, research biologist Bernie Tershy told The Associated Press.

U.S. Fish and Wildlife officials have been using souped-up old technology to catch Asian carp. They use a specialized boat – the Magna Carpa — with giant winglike nets that essentially uses electric current as an underwater taser to stun the fish, said biologist Emily Pherigo.

At higher doses, the fish are killed and float to the surface. In just five minutes, they can collect 500 fish, and later turn them into fertilizer.

Finding new weapons and new methods of control is crucial because invasive species are costly – the federal government is spending millions of dollars each year to protect Lake Michigan and the other Great Lakes from the Asian carp.

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