Bob Downing

Grass carp, a species of Asian carp, appear to be reproducing naturally in the Lake Erie basin for the first time, a federal agency reported Monday.

That news disheartens those involved in trying to keep the invaders out of the Great Lakes.

“We’re concerned about it,” said Rich Carter, executive administrator of the Ohio Department of Natural Resources’ Fish Management and Research.

Ohio will push its partners around the Great Lakes to fill in “knowledge gaps” to get a better picture of how great a threat the grass carp might present and what actions, if any, might be taken to combat them, Carter said.

Commercial fishermen caught four suspect fish a year ago in the Sandusky River in north-central Ohio, the U.S. Geological Survey reported. An analysis showed that the fish, each about 18 inches long, were all at least a year old and had the capacity to become spawning adults, the agency said.

Analysis of bones in the head of the fish showed they lived their entire lives in the Sandusky River watershed, the USGS said.

“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 carp as well,” USGS scientist Duane Chapman said in a statement.

Officials had held out hope that the Asian carps’ specific spawning needs for up to 60 miles of free-flowing streams might preclude them from using the Sandusky and other rivers in northern Ohio.

“The study may also provide resource managers an opportunity to address the spread of grass carp before it becomes problematic,” Chapman said.

Grass carp were brought to the United States to control aquatic plants in the 1960s. They eat large quantities of aquatic plants; however, they could threaten native fish populations and be detrimental to ducks, geese and other large aquatic birds.

Ohio and 42 other states have allowed grass carp to be brought into their respective state to keep ponds and lakes clear of weeds, but only if the fish were sterile.

The state intends to increase its fertility testing of grass carp in the wake of the new discovery, ODNR spokesman Jeff Tyson said.

Grass carp also have been reported in Lake Erie near Monroe, Mich., and in Lake Michigan.

They are closely related to three other carp species: silver, bighead and black carp, which have similar spawning and development requirements. Bighead and silver carp have reached extremely high densities in the Mississippi River Basin and threaten the Great Lakes because they out-compete native fish.

Federal and state agencies have been trying to determine if bighead and silver Asian carp live in Lake Erie or the other Great Lakes.

Tests of environmental DNA, called eDNA, indicate that bighead and silver carp might be present in Lake Erie in low numbers, but searches have not detected any live fish.

In the most recent tests, one eDNA sample of 325 from the Maumee and Sandusky rivers tested positive for silver carp.

State wildlife officials tested for three days in late September for eDNA from the Muskingum River in southeastern Ohio. Those results are expected to be released early next year.

Asian carp have been found in the Ohio River near Portsmouth.

Bob Downing can be reached at 330-996-3745 or bdowning@thebeaconjournal.com.