Thursday, July 30, 2009

Waterworks: Fish Population Assessments


In May and June this year Aitkin DNR Fisheries did an assessment of the fish population on our lake. On a Tuesday evening, May 26th, about 9 p.m., my neighbor noticed a boat crew out on the lake with bright lights, towing a raft near her shore, with some unusual equipment. Next morning we talked it over, and I called Rick Bruesewitz, Fisheries Supervisor, to learn what was going on at Nord Lake. It had been about one hour of “standard electrofishing” for Largemouth Bass, with his fisheries crew cruising near shore, around the perimeter of the lake.
This is what I learned about electrofishing. Using electrical probes, a charge is introduced in the water that attracts and then stuns the bass temporarily. The crew scoops up the unconscious fish and puts them in a towed tank for examination, before releasing them unharmed. The fish are measured and weighed, and a few scales are removed to estimate the fish’s age.
I also learned that this was only the beginning of a periodic population assessment of the fish in our lake. Two years ago Rick had presented an historical summary of the Nord Lake Fishery at our annual lake association meeting, dating from 1960. There would soon be a sampling of all species around the lake. He agreed to let us know in advance when the trap nets and gill nets would be placed in the lake, so that we could notice them and avoid getting tangled up with the floats and nets.


On the week of June 22-26, the three-man fisheries crew returned to set and lift nets around the lake, leaving each net in place for a few days. The trap nets are set near shore, with a float and a trap out in the water and the weighted net bottom attached onshore. The gill nets are deployed out in deep water, between two buoys a short distance apart. Lead-weighted lines hold the base of the gill nets on the lake bottom. During the week boat traffic was light, and we put out the word to residents to steer clear of these orange floats.


Of course, we will not disclose here exactly what was learned. The details of all Aitkin Area fishery population assessments can be viewed at the DNR office next to Southgate on Highway 169. However, a number of Largemouth Bass were collected and released, and the lengths and average weight are in a preliminary report.
There were nine trap net sets and nine gill net sets, during the week. The significant species observed included: Black Crappie, Bluegill, Dogfish, Hybrid Sunfish, Largemouth Bass, Northern Pike, Pumpkinseed, Walleye, and Yellow Bullhead.
Copies of these catches were shared with lake association members at our annual picnic last Saturday. To find out more about fish surveys - when they are scheduled and to learn about the populations on your lake of interest - just call DNR Fisheries at 927-3751.

No comments: