Field Notes: DNR tags 20,000 Mille Lacs walleyes
More than 20,000 walleye were tagged in Lake Mille Lacs in early May in an effort to estimate the lake's walleye population.
The Minnesota Department of Natural Resources worked with the the Minnesota Pollution Control Agency, Great Lakes Indian Fish and Wildlife Commission, Fond du Lac Band of Lake Superior Chippewa and citizen volunteers to tag fish 14 inches and longer.
Walleye were caught in trap nets and by using electrofishing. Each walleye was outfitted with two yellow tags near the base of its dorsal fin. Since May 20, DNR staff have been recapturing tagged walleye using gill nets that are set for less than an hour. As the nets are retrieved, tag data is recorded and all fish are released.
Based on the number of walleye originally tagged and the total number of tagged fish that turn up during the recapture, the DNR can make an accurate estimate of the lake's walleye population. This type of population estimate is used in addition to the gillnet survey conducted each fall.
Recapture work will continue until late June, so anglers should be aware of DNR-netting activity, which may be occurring during the evening. DNR nets are marked with labeled buoys.
Anglers who catch a tagged walleye are asked to leave the tags in the fish and record numbers on both tags by writing down the numbers or by photographing the tags. Consider recording the length of the fish and the location where it was caught. This information can be reported at mndnr.gov/tagged-fish.
In return, anglers will receive information collected at the time the fish was tagged and any information submitted by anglers who may have previously reported the fish.
The effort will provide a better estimate of the lake's population of walleye 14 inches or longer and help guide how many fish can safely be harvested in future seasons, the DNR said. Similar estimates have placed the lake's walleye population as high as 1.1 million fish in 2002 and as low as 249,000 fish in 2014. That decline in the walleye population has led to restrictive regulations, including catch-and-release only fishing this summer, aimed at protecting existing adult fish.
"We anticipate the population estimate being conducted will show a stable walleye population dominated by the (strong) 2013 year class," said Don Pereira, DNR fisheries chief. "The population estimate that is underway also will give us valuable information to help evaluate how well our population model is working."
Hydraulic jets illegal for muck removal
Using hydraulic jets to get rid of "muck" or to uproot aquatic plants in public waters is illegal in Minnesota, the DNR noted last week.
"We remind lakeshore property owners that just because you can buy a hydraulic jet does not make them legal to use in all situations," said Jon Hansen, aquatic plant management consultant. "You may not use them in any way that disturbs the lake bottom or destroys rooted aquatic plants."
Aquatic plants help keep water clean and fish populations healthy. Misusing hydraulic jets can destroy fish habitat and muddy the water. Hydraulic jets, including products like HydroSweep, Aqua Blaster, Aqua Thruster and Aquasweep, can resemble a fan or trolling motor contained in a short tube and create strong currents of moving water.
These products are often advertised to control or remove "muck" and "weeds" from a lake bottom; however, using hydraulic jets in this manner is not allowed in Minnesota.
A person may legally operate a hydraulic jet if it is placed high enough off the lake bed so that it does not disturb the bottom or destroy rooted aquatic plants. It should be directed upward toward the water's surface, which can prevent dead vegetation and duckweed from collecting around docks and boat lifts.
Any displacement of sediment or removal of aquatic plants as a result of operating a hydraulic jet would be deemed a violation and may result in a fine.
Aquatic plant regulations and a guide to aquatic plants can be found at mndnr.gov/shorelandplants. For information on DNR water permits, visit mndnr.gov/permits.