TRAVERSE CITY — Fish were shocked, literally, to encounter biologists conducting a survey of their numbers in the Boardman River.
For two days, a team coordinated by the Michigan Department of Natural Resources electroshocked a 1,000-foot stretch of the river near Brown Bridge Road to see how removal of the Brown Bridge Dam affected fish populations. The dam was removed after a device designed to slowly drain the pond failed on Oct. 6 and sent millions of gallons of pond water rushing down the river.
The resulting flood damaged numerous riverfront properties and prompted lawsuits against several businesses and groups involved in the dam removal project.
Work this week was meant, in part, to determine how the river changes affected fish.
“It’s usually non-lethal,” said Mark Tonello, a DNR fisheries biologist, of the low-voltage shocks.
Tests were conducted Wednesday and Thursday with assistance from the Conservation Resource Alliance, the Grand Traverse Band of Ottawa and Chippewa Indians and other groups. Surveyors donned waders and slowly dragged nets along the river to capture and measure fish.
Tonello said trout fins were clipped for potential down-the-road study, which helps biologists calculate fish populations.
Heather Hettinger, a DNR fisheries biologist with the Traverse City office, said it was too early to tell how dam removal affected fish populations, but early indications are that the river is returning to a more cold-water ecosystem.
Dams disrupt the flow of water and woody debris downstream. In the Boardman River’s case, a century-plus of dams changed the fish community from one that favored cold water to one best-suited for warm water.
Hettinger said the months since dam removal have seen a resurgence of cold-water species like brown and brook trout — a restoration to a more natural balance.
“You definitely see the absence of the dam and its warm water fish communities,” she said.
Hettinger said comparing results of prior surveys also may show the impact of the October dam failure and subsequent flood.