|Coralville Reservoir and dam on the Iowa River near Coralville, Iowa, USA. (Photo credit: Wikipedia)|
A flip of the switch cranks up the generator. Adam Thiese peers over the bow and guard rail; an eight foot dipping net in hand. As long as he keeps a foot on the mat at his feet, a pulse of direct current travels out from the electrodes mounted on the side of the boat…through Coralville Reservoir. A similar safety mat is at the feet of boat operator Chris Mack, a few days ago in the shallows above and below Mehaffey Bridge.
And the electroshocking run is starting to yield results. A couple drum—sheephead—wriggle to the surface. A white crappie, then a couple bluegills, dart erratically off to the side and then float. Thiese acts fast. The fish are not injured; just stunned. He works the net under, scooping them up out of the water. With a lean behind, he flips the net and the fish plop into an on-board holding tank.
Working in 15 minute increments, fisheries workers hit the same stretches every spring. Here—and in lakes across Iowa. Mack is with the Lake Macbride fisheries station; which is responsible for management of lakes and streams in Linn, Johnson, Iowa and three other counties. Thiese is on loan for the day from the Fairport Station, on the Mississippi River.
As the juice is cut, they head towards shore to work up the fish.
“We take lengths, weights; population data to monitor our different lakes and see how our fish populations are doing,” explains Mack. “The obvious thing we can see is year classes; based on the different length of a fish species that we see. Did we have a good spawn the year before? Or was a good spawn a few years ago showing up now with a good up and coming year class?” Water temperature and clarity are also gauged, as they make their entries.
They noted each time an 8- or 9-inch walleye was captured. Most walleyes in the Reservoir are stocked each spring as day-or-two-old fry. The tiny fish are gobbled up pretty heavily, but in a good year, with lots of cover (meaning high water at the right time over shoreline vegetation) there will be more small walleyes like we noticed. The two pairs of fisheries eyes made out a couple same-size saugers, too.
On the next run, a couple big figures turned from underwater shadows to stunned carp. Big ones. But the crew didn’t bite. By the time they were 30 feet away, the 8- or 9-pound rough fish had recovered and waggled back to the bottom.
“Primarily, we are looking at game fish; species we can adjust things for a little. Out here on the reservoir, rough fish are a given. We would spend a lot more time, just picking them up out here,” nodded Mack.
But there were moments.
It seems the speed attained by the guy with the net is directly related to the size of the walleye floating alongside the boat. Thiese was a lightning bolt, hauling on board a 22-incher; one of about six they pulled up, as I rode with them.
“The longest was 22.8 inches, weighing 4.09 pounds,” noted Mack. “We had another, though, 4.71 pounds. It was 22.4 inches.”
A few largemouth bass, some catfish….a couple 12-inch white bass came up on about every run. Not a lot of crappies, though, despite the thought that we were in the middle of the crappie spawn, with females and males moving into spawn.
“Would have liked to have seen more crappies,” admitted Mack. “We just had a little cool down; water temperature dropped. I would suspect as it comes back up, the fish will be coming in.”
That’s why each lake is monitored year after year. One year might suggest a boom…or a bust in various fish populations or growth. Looking back a few years generally shows some ups and downs…but with steady management, they data stays close to normal.
That is what anglers get for their money. The shocking surveys, as well as summer and fall netting surveys…and all fisheries management in Iowa are paid for through their license fees and excise taxes on angling equipment.
I learned years ago not to ask to have them take my picture holding one of the big walleyes. It’s just another day at the office for them.