Fishing for Oxygen

Posted: Thursday, May 10, 2001

FAIRBANKS,Alaska (AP) -- Cal Skaugstad pulled the rope on his power auger and the three-horse motor came alive.

The blade cut into the three-foot thick ice on Quartz Lake, pushing ice shavings out of the hole as it dug deeper. Skaugstad pulled the auger out of the hole once or twice to discard ice buildup and just as he was running out of auger, water gushed up out of the hole as if he had struck oil.

He set the auger aside and pulled a giant, metal briefcase from the back of the one-ton pickup he had driven onto the lake. Opening the case next to the hole in the ice, Skaugstad pulled out a hand-held keypad and began punching in numbers.

A minute later, Skaugstad plugged a long, black cord attached to a 2 1/2-foot tube into the keypad. Taking a plastic cover off one end, Skaugstad dipped the probe into the hole and lowered it by feeding the cord into the hole.

Then Skaugstad turned his attention to the keypad, watching a series of different numbers appear on a small screen.

A sport fish biologist for the Alaska Department of Fish and Game, Skaugstad wasn't looking for fish. He was searching for oxygen, using a high-tech tool called a ''Hydrolab,'' which uses computerized probes to determine water temperature, oxygen content and PH, among other things.

Oxygen is important because fish need it to survive. If the oxygen level in a lake drops too low, the fish die, an event biologists refer to in Alaska as ''winterkill,'' because it happens almost always in the winter when lakes are locked in ice and aren't producing as much oxygen as they do in the summer.

In lakes such as Quartz, which boast an ample supply of plant and animal life called phytoplankton, there is oxygen being produced on a daily basis because of photosynthesis. But the same phytoplankton that is producing oxygen during the day is eating it at night as it decomposes. ''It's kind of a race, how fast the oxygen in the lakes gets used up and when they open up,'' he said. ''It's a balancing act. Some years it's OK and some years it tips over.

Skaugstad, who oversees the stocking of about 1 million fish in 130 Interior lakes, wants to find out which lakes have enough oxygen to keep fish over winter.

''A lot of the lakes we're stocking now are marginal lakes,'' the biologist said. ''We're looking for indications they may be prone to winterkill. ''If they're going to winterkill there's no reason to stock fingerlings because they won't survive to catchable size,'' he said.

It costs approximately $1.50 to raise a hatchery fish from fry to the frying pan.

''Putting a whole bunch of catchables into a lake that don't get caught and will die is expensive,'' Skaugstad said.

Which is where the $3,500 Hydrolab comes in. If the lake can't support fish year round, it will be stocked with fewer fish. ''The bottom line is it saves money,'' Skaugstad said.

Skaugstad found plenty of oxygen in the water when he tested it this spring, leading him to believe that catchable size silvers and arctic char are feasting on the smaller fish.

As a rule, fish need a lake or pond with at least two parts per million of oxygen and not more than eight parts per million.

Biologists have tested 30 lakes in the Fairbanks area and more than half of them have adequate oxygen to overwinter fish, Skaugstad said.

There were some lakes in which biologists found no oxygen at all. When Skaugstad tested North Pole Pond, he thought the Hydrolab was broken because it didn't record any oxygen in the water.

At Quartz Lake, however, biologists have found an interesting phenomenon. The lake is unique in that it is not more than 10 feet deep in most areas, except for a bowl on the south end of the lake that goes down to 40 feet.

Normally in the winter, the amount of oxygen in a lake decreases the deeper you go, which is why ice fishermen catch most fish near the top of the surface in the winter, Skaugstad said. But using the Hydrolab to measure oxygen levels at different depths, biologists have documented that the shallow part of the lake is producing oxygen for the deeper portion.

''Quartz Lake in the winter shows some characteristics we've never seen before because we didn't have the instruments to do readings,'' Skaugstad said. ''You can actually see a river of oxygen flowing into the deeper parts of the lake.''

Prior to the Hydrolab, biologists used kits to collect water samples and then ran chemical tests to determine oxygen levels. Even then, the information they were getting was what Skaugstad termed ''marginal.''

''It took a lot of time and a lot of effort,'' Skaugstad said. ''If you really wanted to be accurate you had to do it in the lab.''

Now, biologists just take the lab with them.


(Distributed by The Associated Press)

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