Officials seek source of Asian carp eDNA
Lansing — Fisheries officials are trying to track down vectors for Asian carp into Lake Erie after eDNA tests conducted this summer showed more signs of silver carp in Maumee and Sandusky bays.
Todd Kalish, Michigan DNR Lake Erie basin coordinator, said state officials are working with their counterparts in Ohio and with the U.S. Fish and Wildlife Service to assess how Asian carp could get into Lake Erie after 23 of 500 water samples collected this summer turned up eDNA evidence of silver carp.
The latest tests confirm results from 2011 that showed Asian carp eDNA in Lake Erie’s Maumee and Sandusky bays, although subsequent electrofishing and netting surveys have not revealed any live fish, officials said.
“What (a positive eDNA test) tells us is that within 24 to 48 hours of the testing there was silver or bighead carp DNA in that area,” Kalish told Michigan Outdoor News. “It doesn’t necessarily mean they were alive.”
Tests for Asian carp conducted throughout the Great Lakes in 2011 revealed six positive eDNA results – four for bighead carp in Sandusky Bay and two for silver carp in Maumee Bay.
State and federal officials then took 500 samples in those areas between June and August of this year, which returned 20 positive results for silver carp out of 150 collected from Sandusky Bay, and three silver carp positives – two in Michigan and one in Ohio – out of 350 samples collected from North Maumee Bay, according to Rich Carter, the Ohio DNR’s executive administrator for fish management and research.
In Ohio, officials “collected additional eDNA samples from around Sandusky Bay and those samples were compromised. So we are evaluating additional sampling in Sandusky Bay and Maumee Bay as part of the path forward,” Carter said, adding that no tests conducted in 2012 showed eDNA for bighead carp.
Electroshocking and other techniques used to catch the invasive carp in the Illinois River were employed in Lake Erie this summer in an attempt to locate any live fish, but none were found. Fisheries officials also have closely monitored commercial fishing reports and other sources, and haven’t discovered any silver or bighead Asian carp in the lake.
“Through all of these activities we are not seeing Asian carp,” Carter said.
Kalish and Carter continue to work with the U.S. Fish and Wildlife Service and experts at Notre Dame University to track possible vectors for Asian carp eDNA into Lake Erie. Possibilities include everything from feces from migrating bird, to contaminated bait fish shops and water transported by boats to areas like the Wabash River Basin, which overlaps with part of the Illinois River Basin – where both species of Asian carp are thoroughly established.
The Illinois and Wabash river basins connect at Eagle Marsh near Fort Wayne, Ind., Carter said, although “it does not appear that Asian carp have bridged that gap and it doesn’t appear that’s a source of eDNA in Maumee Bay.”
Charlie Wooley, deputy regional director for the U.S. Fish and Wildlife Service, said the recent tests weren’t the first sign of Asian carp in Lake Erie.
“We actually came up with three live bighead carp in the west basin of Lake Erie, one in 1995 and two in 2000,” he said.
Tests on those fish showed they grew quickly early in their lives, leading experts to believe the carp didn’t make it there on their own, Wooley said.
“It looked like those fish were from aquaculture ponds down south and somehow were unintentionally or intentionally released into the lake,” he said.
No live Asian carp have been found or reported in Lake Erie since 2000, Wooley said.
“When we find these positive eDNA hits … it’s really perplexing as to how the DNA is getting into the water,” he said.
The USFWS currently is working with Notre Dame to test bait shops in Chicago and other areas for Asian carp eDNA as officials assess their next steps for Erie.
Wooley, Kalish, and Carter agree that the Chicago shipping canal, which connects directly to the Illinois River, is still the biggest threat for Asian carp to get into the Great Lakes, although some experts believe the fish are miles downstream of electric barriers designed to keep them out.
Officials have used underwater cameras to monitor for Asian carp near the barrier, and “we have not seen Asian carp there,” Carter said.
“We’re pretty confident the Asian carp are quite a few miles south of that electric barrier,” he said.