SANDUSKY -- There might be a crisis brewing here, in the waters of the bay and river that share the same name with this Lake Erie city.
The biologists that are the designated guardians of this prolific fishery have put out a plea for assistance. They are looking for a ghost of a needle in a massive, murky haystack, and they are going to need a little help.
Some water samples taken at the end of July revealed the presence of the DNA of silver carp - one of the most dreaded species of the group of invasive fish known notoriously as Asian carp. Out of the 150 vials collected in Sandusky Bay and the Sandusky River, 20 flashed positive for the environmental DNA of the silvers.
This information comes on the heels of a number of positive hits for bighead carp in Sandusky and Maumee bays from an earlier round of samples. An intensive flurry of searching took place after those results came in, but trawling, netting, and shocking failed to produce a single adult Asian carp. The Ohio Division of Wildlife will now repeat those efforts, with assistance of other agencies.
But over this holiday weekend, fishermen are being called on to serve as reinforcements in this search party. Rich Carter, the administrator of fish management and research for the Ohio Department of Natural Resources, said a few thousand more sets of eyes at work hunting for any Asian carp will certainly be welcome.
"We need our anglers to be vigilant in helping us search for the presence of these fish," Carter said Thursday. "Catching a live fish would help us tremendously in determining what the source of these fish is and where they are coming from."
The eDNA method, developed by a group of scientists and mathematicians at Notre Dame, provides researchers with a tool to detect the DNA of the invasive species, but it does not allow them to confirm the presence of live fish, or their number or size. Carter pointed out that the possibility exists that the eDNA could have been transported by storm water, fish-eating birds, bilge water, or other unknown sources.
But the number of positive hits for silver carp eDNA that came from the recent round of testing has alarmed everyone involved in monitoring the Great Lakes for the presence of these destructive fish. Since they are filter feeders, Asian carp consume huge amounts of zooplankton and algae every day, essentially devouring a vital portion of the food column, pushing out the much more desirable native species and dominating the waterway.
"The breadth of positive samples from the Sandusky Bay area was not expected," Michigan Department of Natural Resources Fisheries Chief Jim Dexter said.
"This is not a good sign, for sure," said Chris Winslow, assistant director of Ohio Sea Grant who specializes in the study of invasive species threatening Lake Erie. "I would not go so far as to say we are losing the battle, but we certainly need to ramp up our efforts."
In that vein, Carter has asked fishermen for help. The first step is to go to the www.wildohio.com Web site and find the "Asian Carp Reporting" tab in the center of the home page. A link will then provide very specific descriptions and pictures to help anglers identify the silver and bighead carp.
There have been a few false alarms, with fishermen reporting fish jumping out of the water and assuming they are the silver carp, but Carter pointed out that the silvers take the leaping to a whole new height.
"Anglers need to recognize that other fish jump, but silver carp is a tremendous jumper. They will come several feet out of the water," he said.
The biologists want reports on any possible sightings of Asian carp, and there is a link on the Web site for this, and if an angler manages to catch one of these invasive fish, Carter asked that they report it immediately and keep the fish alive, if possible.
"It is also very important that we have photos to document the specimen," he said. "We're asking anglers for help, and we will take any fish that anglers provide."
Carter said the various state and federal agencies that are teaming up to monitor the potential presence of Asian carp in Lake Erie and surrounding waters are intent on determining what the source of the eDNA is, but for now there is a degree of uncertainty over what the information is telling them.
"We have not seen any live fish, so if these fish are present, they are likely present in very low numbers," Carter said. "But it is our job and our responsibility to keep looking."
Contact Blade outdoors editor Matt Markey at: firstname.lastname@example.org or 419-724-6068.