Northern Snakehead Appears in Burnham Harbor

Lake Michigan received an unwelcome visitor last October when a fisherman caught a fish native to Asia in Chicago's Burnham Harbor. The northern snakehead, Channa argus, has already made appearances in Maryland and Virginia, and its presence has ecologists on edge.

While not every species that invades is destined to become a pest, the snakehead has a reputation for destruction. "They can be really aggressive predators, and they're voracious eaters," said Kristin TePas of the Illinois-Indiana Sea Grant program. The snakehead's most alarming and bizarre feature makes it a high-risk invader as well: snakeheads are capable of migrating across land - using their pectoral fins to move - and are able to survive out of water for days.

The captured snakehead ended up at The Field Museum, which determined that it was a female without eggs. "It is possible she had eggs in the past, but there is no way to know for certain," the museum's Phil Willink said.

Scientists haven't found any additional snakehead fish since, despite using electroshocking and net sampling to monitor the area. "We do assessments for other species along the lake," said Tom Trudeau, the Lake Michigan program administrator for the Illinois Department of Natural Resources, "and we'll be looking for snakehead." He described the fish's favorite habitat as shallow water with heavy vegetation, which matches several area harbors.

Snakeheads are frequently used in aquariums and in live food markets, despite being banned in Illinois and other states. Scientists suspect that the one found in Burnham Harbor was dumped there. "That's what we're hoping," Trudeau said, "but we have to work on the assumption that there are more."

— Allison Knab