Steering the boat toward a jumble of trees on an inside bend,
Iowa Department of
Natural Resources fisheries technician Greg Simmons was confident. "It's in
that logjam. As we get closer, the beeping will get louder," said Simmons.
Unplugging the electronic box from the mast, Simmons held it over the side
of the boat. The beeps were loud and sharp. "It's right below us," offered
Simmons. "1702 was tagged August 20 of last year. The last time we 'saw' it
was this May (probably moving up from its wintering area) just above the
mouth of the Cedar River. So it's moved up about ten miles since then."
As Simmons recorded depth and other details, it was easy to see why the
fish was here. On the inside bend there would be a couple nice holes. The
tangle of flood-carried trunks, stumps and limbs created blocked the
current, creating a calm area, good habitat for smaller river fish...and
the flathead catfish that would swallow them. Across the river, the outside
bend showed sloughed-away dirt banks, a reminder of the changing nature of
the stream and the multitude of organisms it supports.
Crews last year caught and implanted radio-transmitters in 35 flatheads.
This trip was just for telemetry. "The receiver here will pick up signals
from the fish," explains Simmons. "Each one is assigned a different
frequency. If the scanner doesn't pick up a frequency in the two-second
interval, it moves to the next one." It had been a pretty good day.
Starting at the Burlington Street Dam in Iowa City on this day, Simmons had
located 14 'electronic flatheads' by the time he pulled out at River
Junction, east of Riverside. DNR biologist Greg Gelwicks had started there
and was monitoring downstream. The research crew, out of Manchester, spent
the night and completed their run down to the Mississippi the next day.
On a different trip, they might electroshock the same stretches; a method
that brings up smaller flatheads. Or, they would set underwater hoop nets,
especially during spawning, to get more of the monsters. They need to see a
representative sampling of the flatheads to gauge just how many are out
there. Concerns from anglers not seeing as many big flatheads prompted the
multi-stream survey. As the top predator, a balanced flathead population is
critical to a river's overall health. And if you've ever wrestled a
five--or 45--pound flathead to the bank, you know why many river anglers
Similar work is underway in the North Raccoon, Des Moines and Cedar River
corridors in Iowa. That includes some attention to tributaries. Just prior
to pushing off, Gelwicks talked by phone with a woman who had caught one of
the transmitter-fitted fish on the English River, near North English.
Though there is nothing illegal with taking one home-they know of four
caught--biologists urge anglers to contact them to pin down location,
movement and other data. Plus, they'll stop searching for that frequency.
In its second year now, the study is showing that habitat is critical...and
that fish will move to get to that habitat. For instance, why did 1702 swim
past 10 miles of the Iowa River to get back to that particular logjam above
River Junction? "A fish might do well for ten months out of the year but if
it lacks critical habitat, an over-wintering area for instance, it is going
to have to (search for it)," cautions Simmons. "We just don't know a lot
about flatheads on our interior streams. We are looking at how far they
move at different times of the year. We want to learn about population,
growth rates, too; some simple parameters to tell us more."
And through the implanted radio transmitters, the catfish are talking.