04-29-2004, 03:56 AM
More than 10 percent of North Dakota's lakes experienced some form of fish die-off this past winter, a significant, but not record-breaking occurrence, according to Terry Steinwand, fisheries chief for the State Game and Fish Department.
The die-offs occurred when heavy snow cover on the ice prevented sunlight from reaching oxygen-producing aquatic plants, lowering dissolved oxygen to levels that could not support fish. "It's a matter of an oxygen balance," Steinwand said. "We have a large amount of nutrients and sediments entering our lakes. This produces some large algal blooms as well as excessive aquatic vegetation. When these plants die off and start decomposing they utilize oxygen. When more oxygen is consumed than produced, oxygen levels decline to a point where fish mortality occurs."
Even though more than 10 percent of the lakes saw some die-off, 2004 doesn't compare to the record winter kill of 1982, when 30 percent of the lakes had substantial winter kill, Steinwand said. "And at that time we had only about 150 lakes in the state," he added. "Now we have more than 300."
Fisheries personnel have already started restocking efforts on some lakes that experienced winter kill. "This is not a desirable method of sustaining a fishery," Steinwand said, "but sometimes you have to play the cards you are dealt."
The majority of winter kill lakes were found in the northern half of the state and particularly the northwest, Steinwand noted. "It is not surprising since that is the portion of the state that received the most snowfall," he added.
There likely was some winter kill at other lakes, Steinwand said, but the department won't know the extent until personnel are able to set nets to determine fish populations in remaining lakes.
A lake with significant winter kill means that most, but not necessarily all, fish died. Lakes experiencing significant winter kill were Arena-Harriet Lake and Mitchell Lake, Burleigh County; Carbury Dam, Bottineau County; Holocek and Spring Lake, Bowman County; Tanberg Dam, Divide County; Castle Rock Dam and Mott Watershed, Hettinger County; Marion Lake, LaMoure County; Kautz Lake and Wentz WPA, Logan County; Brush Lake, McLean County; Stanley Pond and Stanley Reservoir, Mountrail County; Balta Dam, Pierce County; Belfield Dam, Stark County; Alkali Lake and Ruele Lake, Stutsman County; Fairgrounds Pond and Makoti Lake, Ward County; Harvey Dam, Wells County; Kettle Lake and Tioga Dam, Williams County.
Partial fish kills were at Mirror Lake, Adams County; Powers Lake and Northgate Dam, Burke County; Skjermo Lake, Divide County; Juanita Lake, Foster County; Blickensderfer Dam, Hettinger County; Lake Helen, Kidder County; Mudd Lake, McIntosh County; Leland Dam and Sather Dam, McKenzie County; Crooked Lake, McLean County; Gulleson Pond, Sargent County; Bentz Lake, Sheridan County; Rice Lake, Ward County; Cottonwood Lake, Iverson Dam, McGregor Dam, McLeod Dam, and West Spring Lake, Williams County.
These lakes will be re-stocked as soon as possible either with hatchery raised fish, or fish transported from another lake with an abundance of the preferred species. "We'll be evaluating these lakes as we always have and determine what can be done to lessen the frequency of these events," Steinwand said.
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The die-offs occurred when heavy snow cover on the ice prevented sunlight from reaching oxygen-producing aquatic plants, lowering dissolved oxygen to levels that could not support fish. "It's a matter of an oxygen balance," Steinwand said. "We have a large amount of nutrients and sediments entering our lakes. This produces some large algal blooms as well as excessive aquatic vegetation. When these plants die off and start decomposing they utilize oxygen. When more oxygen is consumed than produced, oxygen levels decline to a point where fish mortality occurs."
Even though more than 10 percent of the lakes saw some die-off, 2004 doesn't compare to the record winter kill of 1982, when 30 percent of the lakes had substantial winter kill, Steinwand said. "And at that time we had only about 150 lakes in the state," he added. "Now we have more than 300."
Fisheries personnel have already started restocking efforts on some lakes that experienced winter kill. "This is not a desirable method of sustaining a fishery," Steinwand said, "but sometimes you have to play the cards you are dealt."
The majority of winter kill lakes were found in the northern half of the state and particularly the northwest, Steinwand noted. "It is not surprising since that is the portion of the state that received the most snowfall," he added.
There likely was some winter kill at other lakes, Steinwand said, but the department won't know the extent until personnel are able to set nets to determine fish populations in remaining lakes.
A lake with significant winter kill means that most, but not necessarily all, fish died. Lakes experiencing significant winter kill were Arena-Harriet Lake and Mitchell Lake, Burleigh County; Carbury Dam, Bottineau County; Holocek and Spring Lake, Bowman County; Tanberg Dam, Divide County; Castle Rock Dam and Mott Watershed, Hettinger County; Marion Lake, LaMoure County; Kautz Lake and Wentz WPA, Logan County; Brush Lake, McLean County; Stanley Pond and Stanley Reservoir, Mountrail County; Balta Dam, Pierce County; Belfield Dam, Stark County; Alkali Lake and Ruele Lake, Stutsman County; Fairgrounds Pond and Makoti Lake, Ward County; Harvey Dam, Wells County; Kettle Lake and Tioga Dam, Williams County.
Partial fish kills were at Mirror Lake, Adams County; Powers Lake and Northgate Dam, Burke County; Skjermo Lake, Divide County; Juanita Lake, Foster County; Blickensderfer Dam, Hettinger County; Lake Helen, Kidder County; Mudd Lake, McIntosh County; Leland Dam and Sather Dam, McKenzie County; Crooked Lake, McLean County; Gulleson Pond, Sargent County; Bentz Lake, Sheridan County; Rice Lake, Ward County; Cottonwood Lake, Iverson Dam, McGregor Dam, McLeod Dam, and West Spring Lake, Williams County.
These lakes will be re-stocked as soon as possible either with hatchery raised fish, or fish transported from another lake with an abundance of the preferred species. "We'll be evaluating these lakes as we always have and determine what can be done to lessen the frequency of these events," Steinwand said.
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