After repairs, Knife River fish trap to be in operation soon
The Knife River churned and frothed toward Lake Superior in full run-off mode Tuesday morning.
After some final tweaking last week, the trap is expected to be in operation for this spring’s spawning run of Lake Superior rainbow trout, said Blankenheim, anadromous fish biologist with the Minnesota Department of Natural Resources.
The fish trap, which allows biologists to monitor both upstream and downstream passage of rainbow trout, was repaired this winter after being damaged in the June 2012 flood.
DNR senior engineer Jon Hendrickson looked on as Blankenheim cranked open the big aluminum gate.
“We have more ice in the trap than we’ve ever had,” said Hendrickson, who supervised reconstruction of the trap for the DNR. “We’re trying to manipulate the gates to bring water in to melt and erode the ice.”
Electricians also worked last week to restore power to the repaired trap.
The trap, which sits on the west side of the Knife River just downstream from the Minnesota Highway 61 expressway, was damaged when the structure’s holding compartments were inundated by rocks and boulders that washed into it during the June 2012 flooding. Many of the trap’s adjustable gates were damaged by the debris and had to be replaced.
The repairs cost about $450,000, said Don Schreiner, DNR Lake Superior area fisheries supervisor. Of that total, 75 percent was reimbursed by the Federal Emergency Management Agency.
“There’s all sorts of habitat work going on in the Knife River system. This is the one tool we can use to evaluate the health of the watershed as a whole,” Schreiner said.
The trap first began operating in 1996. Part of its purpose was to help biologists determine why the rainbow trout (steelhead) population had been declining since the 1980s. The trap allows biologists to better understand how many rainbows return to spawn in the Knife and how many young trout migrate down to Lake Superior.
Members of Trout Unlimited said last year they supported the DNR’s decision to repair the trap. But members of the Lake Superior Steelhead Association said they thought money would be better spent on research upstream to learn why more young trout aren’t surviving.