WIKIMEDIA, ENGBRETSON, ERICAs several species of Asian carp have spread throughout waterways in the central U.S., one of the biggest fears has always been that they would make it to the Great Lakes. Already in areas where the fish have invaded, carp have wreaked havoc on ecosystems. The U.S. Geological Survey (USGS) reported last week (October 25) that four grass carp have lived their entire lives in Ohio's Sandusky River, a tributary of Lake Erie.
“It's bad news,” Duane Chapman, a USGS fisheries biologist and member of the research team, told the Associated Press. “It would have been a lot easier to control these fish if they'd been limited in the number of places where they could spawn. This makes our job harder. It doesn't make it impossible, but it makes it harder.”
Chapman and his colleagues found several pieces of evidence, which they published in the Journal of Great Lakes Research, pointing to a breeding population in the Sandusky River, rather than individuals that entered the river from aquaculture. For one, it is illegal to release diploid carp into the Great Lakes watershed, and at least two of the fish found there were diploid. Second, the bones in the carp ears showed elevated ratios of strontium to calcium, reflective of the high strontium levels in the Sandusky River.
Although the grass carp are less of a concern than other species of Asian carp, the findings are a troubling harbinger. Successful breeding of grass carp means that the environment might be favorable to other species, such as silver, bighead, and black carp. “These findings are significant because they confirm recent USGS research indicating that shorter rivers, like the Sandusky, are potential spawning sites for grass carp and other Asian carps as well,” Chapman said in a press release.