Electrofishing for answers in Michigan [video]
On a rainy August morning, three men dressed in dark-shaded green chest waders and rain jackets slowly make their way upstream, through the chilly waters of the Rock River in Alger County.
Two of the men carry long white poles with rectangular boxed ends in one rubber-gloved hand and a fishing net at the end of a wooden pole in the other.
From each of the two men, a thick yellow electrical cord runs downstream to a blue or red equipment box in a small aluminum boat, which is being pulled up the river by the third man.
As the men move the ends of the white poles under the stream banks, and the wet alder trees overhanging the water, large and small brook trout begin to appear, floating sideways or upside down in the creek.
Quickly, the fish are netted and moved to a plastic bin filled with water that’s sitting in the bottom of the boat. The men pull the boat to the muddy shore and they begin measuring the fish and collecting information on each of them.
They work quickly because it won’t be long before the fish have revived and are once again darting under the banks of the stream, looking for places to hide.
This process is called electrofishing, and it’s been around for quite a while. The men and women who perform this task for the state are fisheries biologists and technicians with the Michigan DNR.
Uses of the technology
For decades, fisheries managers have used electrofishing gear to grow their knowledge about the fish community that lives in each stream or lake.
The many uses for electrofishing gear, illustrating why it is a critical tool for fisheries managers, include:
Aiding in estimating the number and type of species living within fish communities.
Collecting wild fish for egg gathering. The eggs are taken to fish hatcheries and hatched. The fish produced from these eggs are used for stocking streams and lakes.
Providing data to help judge the effectiveness of fisheries management actions.
Monitoring important fish species or non-native, invasive species that can harm fish populations, water quality, recreation or economic concerns.
In the early 2000s, the DNR’s Fisheries Division developed a standard process for stream sampling to compare fish populations between different streams with similar habitat types. Electrofishing gear is used to collect information from the populations in these streams.
Typically, information fisheries biologists, technicians and managers are looking for includes length, fish species type and age. They often will take scale or spine samples to help determine age.
Under a rotation plan – three years of stream sampling, three years without – the Rock River in Alger County, is sampled using the established standard method. The stream contains a wild population of brook trout.
By sampling within a 1,000-foot length of stream, a population estimate for brook trout is calculated from each sampling effort. From the information gathered, trends in brook trout abundance, mortality and growth can be identified, which are key components to fisheries management.
Every year during spring runoff, rivers rise, swollen with snowmelt. In Newaygo County, the DNR’s Fisheries Division organizes a fleet of electrofishing boats to head to the Muskegon River, below Croton Dam, in search of walleye.
The Muskegon River serves as one of two locations in Michigan where wild walleye brood stock (eggs used to grow fish populations) is collected. The second is Little Bay de Noc in Delta County.
Because of the high and fast water conditions of the Muskegon River during the spring spawning run, electrofishing boats are very effective at successfully capturing spawning walleye. This provides the number of eggs needed to meet targets for production at the Wolf Lake State Fish Hatchery in Van Buren County.
Additionally, about one month later, on the east side of Michigan, electrofishing boats search the Detroit River for muskellunge during their spawning period. Great Lakes, or “spotted,” muskellunge have been the primary focus for DNR Fisheries Division production since 2010.