Various visitors cause trouble in the U.S.

Non-native species have caused and continue to cause trouble across the United States and close to home.
Coming up from the South, fire ants inch closer to the northern states year by year and, just recently, a colony of the pests was found in an area of a state thought to be too cold for them.
Killer bees have made their way up from South America and have caused problems for those who rely on the honey bee for pollination as well as for innocent bystanders who disturb the short-tempered insects.
In Lake Erie, the zebra mussel has seemingly colonized nearly every inch of underwater space. The unwanted bivalve may have helped to make the lake clearer, but it is also being looked at as a possible culprit in a growing dead zone in Erie's Central Basin. It also competes for plankton, the small animal and plant life that many sportfish also feed on.
Another 'invader'
Now comes word of another non-native species, one that could wreak havoc on Great Lakes sportfishing.
Many sources have reported that a fish called the Asian carp is close to breaking out of tributaries and finding a home in Lake Michigan.
A Knight Ridder story recently described the fish as "a humongous plankton-gobbling fish that has been dubbed the underwater lawn mower."
The story said that the fish can grow to more than 100 pounds and 4 feet long. These dimensions, the story said, enable the fish to outcompete even the most aggressive sportfish for available resources. The carp's favorite food is plankton and it can eat up to three times its weight daily.
The fish is not native to this country but was brought here from China in the early 1970s as a method of controlling algae and improving water quality. It escaped from fish farms in Arkansas during flooding by the Mississippi River in the 1990s and started its migration up the river toward the Great Lakes.
According to news reports, officials have placed an electric fence along one waterway that connects the Mississippi and Lake Michigan. A second such barrier or others made of carp-repelling bubbles or sound waves are under consideration.
Worst case
The Knight Ridder report quoted one official about the carp's potential impact to the Great Lakes: "The worst case is that they would find it very suitable and very much to their liking, and they would grow to huge population numbers and compete with sportfish like yellow perch, walleye and smallmouth bass," said John Rogner, field supervisor of the U.S. Fish and Wildlife Service office in Chicago.t
Meanwhile, back in Lake Erie, U.S. Fish & amp; Wildlife Service crews will be working on the Grand and Chagrin rivers in Lake County, Ohio, in an attempt to control another "invader," the sea lamprey.
The parasitic lampreys accessed the Great Lakes in the 1800s through the canals that link the Great Lakes with the Atlantic Ocean.
The creatures latch on to healthy fish, create a hole with their raspy, sucking mouths, and basically eat off the host fish. The host fish eventually weaken and sometimes die.
Work began by the Great Lakes Fishery Commission in the 1950s to control this pest use a chemical lampricide. The program was so effective it grew to include all the Great Lakes.
Survey the rivers
The crews on the Grand and Chagrin will survey the tributaries to gauge if there are sea lamprey larvae growing there. The lampricide used forces larvae out of burrows and to the surface where they can be caught and a count estimated. The chemical is not harmful to humans, pets, livestock, mammals or birds, the USF & amp;WS reported.
According to the USF & amp;WS report, "The Sea Lamprey Control program continues to contribute significantly to the $4 billion sport and commercial fisheries that exist in the Great Lakes. Without continued control efforts, these fisheries again would be in jeopardy."
braun@vindy.com