By Nick Simonson
To say this winter has been unusual would be an understatement. According to the University of Illinois’ Midwestern Regional Climate Center, this winter has tracked along the line of that season in 2011-2012 as the all-time mildest for Bismarck, and remains in the very mild category for Fargo. While the general population has been enjoying easier movement, less shoveling, and firmer footing when walking about, the state’s wildlife and fisheries have benefitted from the moderate conditions experienced through the halfway point of the season. On the latter, the North Dakota Game & Fish Department (NDG&F) Fisheries Management Section Leader Scott Gangl finds optimism heading into the back half of the season.
“In terms of fish health, that mild winter is generally going to help them out in surviving the winter and making sure that they get through the winter without many risks of winterkill…that should be very positive for the state’s fish populations,” Gangl commented.
The biggest concern for ice-covered lakes each winter in North Dakota is winterkill, particularly for those smaller lakes throughout the southeast and south-central portion of the state, along with those western reservoirs which dropped significantly after a drier summer. In those sloughs and other potholes which have grown in size and depth over the past few decades where fish like walleyes, perch and pike are stocked, angling can be a boom-and-bust scenario. The boom comes from high water situations which not only provide a viable fishery, but also support natural reproduction of species like perch and pike which utilize flooded vegetation on which to lay their eggs. The bust sometimes happens when harsh winters with cold temperatures, thick surface ice, and lots of snow result in winterkill.
“When there’s no snow covering the ice, sunlight can penetrate through the ice and [plants] can still give off oxygen, they can still go through their life cycle and plants can photosynthesize,” Gangl explains, adding, “you end up with a situation where there’s more oxygen consumption than there is production when there is a heavy snow cover, and eventually the lakes will run out of oxygen, there just won’t be any oxygen in the water and that leads to fish kills,” he concludes, referencing that generally only the most hardy fish like carp and bullheads survive partial winterkills, but even they can succumb if conditions get too harsh.
Gangl explains that the agency’s staff will begin sampling dissolved oxygen levels in the state’s lakes in February as they do most every year. The results this season, however, aren’t anticipated to be as alarming as in seasons past, and winterkills of a full or even partial nature are not expected based on the recent conditions and much of the state not receiving significant snowfall, which accelerates plant death and decreases dissolved oxygen content in the water. While the lack of snow can be good for winter survival, that lack of spring runoff resulting from it may impact spawning of certain species in those lakes and flows where natural reproduction occurs and sustains the fishery.
In places like Lake Oahe, where walleyes are self-sustaining and on waters like Devils Lake where stocking is only part of maintaining a fishable population of the state’s most favored angling target, the lack of runoff may decrease the success of this spring’s spawn. However, Gangl advises that, in Oahe particularly, there are many strong year classes to sustain the fishery, even if this spring doesn’t turn out to be ideal on the water.
“In the Missouri River system, we could probably see some lower reproduction in places like Lake Oahe where we do have a naturally reproducing population [of walleyes],” Gangl projects, “we’ve seen several good year classes in the last five years, so it probably won’t hurt the population overall to take a year off and maybe have a few less fish out there, because there are already a lot of mouths to feed,” he continues, referencing the large population of smaller walleyes showing up in the agency’s sampling and competing for the water’s limited forage.
On those lakes where stocking has helped expand anglers’ options for walleyes, it will likely be business as usual, and another spring of increased demand is likely as the size and number of lakes grow across the state. The NDG&F will resume its egg collection operations on Lake Sakakawea and potentially Devils Lake and Lake Oahe, if necessary, in April and the agency will partner with federal fish hatcheries at Garrison Dam and Valley City to rear young walleyes to be stocked in late June, when they are one-and-a-half to two inches in length, thus continuing the cycle – and good fishing expanding across the state – regardless of how tough the second half of winter might be.
Featured Photo: With expanded stocking, anglers can expect more good walleye fishing throughout North Dakota in the coming years. Simonson Photo.