The fish pulled out of Burnham Harbor was so strange looking that the angler who caught it posted its picture on the Internet.
Long and slender, with a grotesque mouth full of razor-sharp teeth, the creature at first glance looked like a mottled cousin of the northern pike, a fish commonly found in Lake Michigan. But when scientists around the country saw the fisherman's grainy image, they immediately suspected that one of the nation's most feared ecological invaders--the northern snakehead--had arrived in the Great Lakes.
On Thursday state biologists confirmed the discovery after picking up and examining the 18-inch predator, which had been packed in ice.
Biologists worry the fish could be the leading edge of a new form of biological pollution in the world's largest freshwater ecosystem, one that could rival existing threats such as sea lampreys and zebra mussels.
Native to China, Korea and Russia, the jut-mouthed northern snakehead is a voracious eater noted for its aggressive attempts to crowd out competitors. It feeds on small fish that make up the diet of salmon, perch and other fish already in the lake and will devour virtually anything else it can find.
The snakehead also is different from most other fish in the United States. It breathes air in addition to extracting oxygen from water through its gills, a trait that enables the fish to survive out of water for days, and it can squirm short distances to another body of water.
In addition, it's hardy enough to make it through winter, slowing its metabolism so it can survive beneath the ice.
"I hope that is the only one they find in Lake Michigan," said Walter R. Courtenay Jr., a snakehead expert at the U.S. Geological Survey. "If there is a male and female out there, anything can happen."
State officials think that snakeheads, which prefer shallow, grassy areas close to shore, aren't likely to compete with salmon swimming in deeper parts of the lake. But they are worried that it could devastate what is left of the dwindling population of yellow perch in Lake Michigan. Snakeheads also would compete viciously with other sport fish in the Great Lakes, such as bass and walleye.
"I don't think any of our native fish can wipe out the snakehead," Courtenay said.
Made a splash 2 years ago
Snakeheads first swam into the national spotlight two years ago when an angler pulled one out of a pond behind a Dunkin' Donuts in Maryland. Biologists have since found what appear to be reproducing populations in the Potomac River in Virginia, a South Philadelphia lake that feeds into a tributary of the Delaware River and a pond in eastern Massachusetts.
Maryland officials were so concerned about the fish that they poisoned the entire pond, but that wouldn't work in the Great Lakes.
Once an obscure creature in Asian fish markets and exotic pet shops, the snakehead now is vying with another troublesome import--the Asian carp--as the biggest threat to native fish and the nation's multibillion dollar commercial and sport fishing industry.
Snakeheads are so aggressive that they thrash out of aquariums when agitated. They attract some pet owners who see them as the pit bulls of fish.
Federal officials are so concerned that they prohibit bringing snakeheads or their eggs into the country, carrying them across state lines or dumping them into waterways. Illinois and Chicago imposed snakehead bans two years ago in the wake of the Maryland incident.
"The problem is they can show up anywhere," said John Rogner, field supervisor for the U.S. Fish and Wildlife Service.
The fish scooped out of Burnham Harbor with a net last weekend was estimated to be about 3 years old, making it mature enough to reproduce. Scientists won't know if the fish was a male or female until it thaws and they can dissect it.
Getting rid of snakeheads could be practically impossible if the fish has managed to spread, said Courtenay. Scientists say mature females can lay up to 75,000 eggs a year.
Sweep of harbor planned
State officials are scrambling to pull survey crews out of other lakes and rivers to scour the harbor for snakeheads. They plan to use boats equipped with electric cables that shock fish and bring them to the surface, but one state official cautioned that the technique generally only works to a depth of 3 feet and could miss some fish in the deep harbor.
"I'm hoping this is just a random fish dumped out of an aquarium by somebody who didn't know what to do with it," said Tom Trudeau, head of the Lake Michigan fisheries program at the Illinois Department of Natural Resources. "The fear is seeing their young in the lake. If that happens, we're in trouble."
Acting quickly could make a difference, experts said.