Catch a Hundred Bucks

ODNR tracking Sandusky River walleye
May 21, 2014
Written by
Kristina Smith
Watchdog/enterprise reporter
FREMONT — Last month, the Ohio Department of Natural Resources fitted 100 walleye with tags
and transmitters and dropped them into the Sandusky River.
For the next four and a half years, ODNR will be able to track their movements, body temperature
and mortality, said Chris Vandergoot, fisheries biologist supervisor at ODNR’s Sandusky Fish
Research Unit.
Every time a fish swims by one of the receivers downstream in the Sandusky River or in various spots
on Lake Erie, ODNR will have a note of it.
The agency also shares information with others who have receivers on other rivers and Great Lakes,
so it will know whether the fish are staying in Lake Erie or moving on to new scenery.
“It’s giving us insight into what they do and how long
they do it,” Vandergoot said. “It shows us what kind of
preferences they have and what their habits are.
“It opens our eyes on what these things are doing and
how it may differ from our preconceived notions.”
And fishermen who catch a tagged walleye receive a
$100 reward if they return the transmitter to ODNR.
That helps the agency track how many were caught.
All of this information helps ODNR and other agencies
in states that border the lake set quotas for how many
walleye can be harvested from Lake Erie without harming the population, he said. Walleye are one of
the most economically important fish on Lake Erie and one of the most sought-after game fish.
“It also gives us an idea if there are certain stocks we need to protect,” Vandergoot said of the
research.
Different stocks of walleye spawn in the Sandusky River, the Maumee River and the Lake Erie
Western Basin reefs near the Davis-Besse Nuclear Power Station and Camp Perry areas.
ODNR has tagged and released walleye in other areas, including the Maumee River and Western
Basin reefs in recent years. The ones released into the Sandusky River are specifically being studied
to determine how they respond to the potential removal of the Ballville Dam in Fremont.
Fremont City Council must determine whether to remove or repair the dam, which ODNR believes is
blocking important spawning ground upstream toward Tiffin that walleye and other fish would use. It
also is keeping the gravel that walleye, white bass and other fish like for spawning habitat below the
dam from replenishing itself, Vandergoot said.
If the dam is removed, ODNR can see if the fish actually do spawn further upstream and better track
the habits of the spawning stock. If the dam stays, ODNR can still use the data to get a better idea of
what the walleye are doing, he said.
There are about 600 tagged walleye that were placed in various locations on Lake Erie and its
tributaries, he said.
By monitoring the fishes’ body temperature, ODNR can get an idea of when it migrates to colder
water. Fish are cold-blooded, so their body temperature rises and lowers with the water temperature.
Walleye are a cool-water fish, so they move out of the rivers after spawning because the water
becomes too warm. They also migrate out of the Western Basin to the colder, deeper waters of the
Central and Eastern basins in the hot summer months.
What researchers have noticed so far in some of the tagged fish is that they show quite a variance in
temperatures. Data from the transmitter showed in one fish that its body temperature would rise and
lower by 12 degrees in short periods of time, Vandergoot said.
That indicates the fish might be moving up and down in the water column — from warmer water near
the surface to colder, deeper water — from near shore water to deeper water, he said.
The fish could be conserving energy through this process, or they could be feeding or both, he said.
“They’re probably trying to find their thermal preference or optimum,” he said. “It’s helping us get
insight into it. It may explain why walleye in Lake Erie are so big.”
Lake Erie conditions are ideal for walleye because the conditions include access to cool water, good
spawning habitat and plenty of places to forage for food, he said.
“It’s hard to script out a better place for walleye than Lake Erie,” he said.
The Sandusky River study is funded through Ohio Sea Grant and the Great Lakes Restoration
Initiative. The receivers throughout the Great Lakes are used in a variety of projects across the
region, including monitoring of sturgeon, trout and invasive sea lampreys, Vandergoot said.