For years, North Dakota Game and Fish Department fisheries biologists have been taking dissolved oxygen samples to determine how fish are surviving winter.
This photograph, taken in February 1967 on Lake Upsilon in the Turtle Mountains, pictures Royce Johnston, Department fisheries technician, driving the snowmobile. His passenger is Alven Kreil, Department northeast fisheries biologist. The wooden sled behind them holds an auger, equipment to take water samples and a heater to keep the samples from freezing.
It turns out that winter 1967 was tough in terms of how it was affecting the state's fisheries. 'Indications from winter oxygen analysis, however, point to the most severe losses in many years. Hardest hit was the northeastern part of the state, with many lakes undoubtedly suffering severe mortalities,' according to May 1967 North Dakota OUTDOORS.
Fast forward nearly 50 years and interest in dissolved oxygen levels in North Dakota fishing waters still exists, as biologists sample as many waters as possible to give anglers an idea how fish are overwintering in their favorite waters.
The difference between determining dissolved oxygen levels today compared to 1967 is night and day, said Greg Power, Department fisheries chief.
Back in the day, fisheries biologists would hit a handful of waters in a day before having to head back to their district office and spend yet another full day in the laboratory.
'It was very labor intensive because biologists back then had to run through a number of procedures to determine dissolved oxygen levels of the waters they tested,' Power said.
With today's electronic technology, water quality sampling provides instant information and a higher degree of accuracy. In addition, 10-12 lakes can be sampled each day.
Just getting to the deepest part of the lake where biologists often like to take water samples is much easier today than nearly a half-century ago.
'With our lakes being mapped and with the use of GPS today, our biologists don't have to drill a bunch of holes in the ice to find the deepest part of the lake,' Power said. 'They can go right to the spot … it's so much more time efficient.'