Flood waters frustrate key northern Minnesota sturgeon count

Flooding's taking a toll on northern Minnesota's lakeshores and riversides, but it's also playing havoc with important research beneath the water's surface.

Flooding's forced delays in the state's once-a-decade sturgeon count — a census on the health of a fish vital to northern Minnesota. Officials say they're confident they'll find robust sturgeon numbers. But the high water has hampered the count.

Every 10 years gill nets sanctioned by the Minnesota Department of Natural Resources pull hundreds of sturgeon from the Rainy River and Lake of the Woods. Those fish are tagged in the spring, with a second crop caught later in the summer. It's an important effort to ensure sturgeon numbers don't collapse as they did at the turn of the last century, when overfishing and pollution slashed the population here and around the world.

Environmental regulations begun in the 1960s have helped restore the Rainy River sturgeon and the 10-year count is meant to keep it that way.

Early this spring, DNR researchers from stations stretching from the dam at International Falls, down the Rainy River and in to Lake of the Woods caught something in the neighborhood of 1,300 sturgeon. They were marked with plastic tags wired through the base of each dorsal fin and released.

The plan was to let the tagged fish mingle with non-tagged fish for about a month before the second round of gill netting. Crews finished tagging in May and were readying the boats again when the Rainy River started its precipitous rise. Based on the number of recaptured tags, the DNR would estimate the sturgeon population.

Now, weeks later, researchers are catching some sturgeon on Lake of the Woods, but the Rainy River is still too high and fast for netting. By the time it slows, the water will likely be too warm for netting.

At this point, the study won't be completed until October.

For most fish, such a long delay would throw off the numbers, said DNR large lake specialist Tom Heinrich. Tagged fish might die in that time, inflating population estimates. Sturgeon can live up to a century but that long life cycle makes the fish susceptible to environmental changes and over fishing.

Heinrich, though, called the region the most robust sturgeon system on the continent and said he believes the finished study will still show a healthy population of the hefty bottom feeders.

"The sturgeon of Rainy River and Lake of the Woods, we believe, are thriving," he said, though, "there's a pretty large number of species of sturgeon all across the world and the vast majority of those species are in decline."

In 1990, there were just 17,000 fully grown adults in the Rainy River and Lake of the Woods. In 2004, there were 59,000. Heinrich believes the numbers are still growing, although thanks to the record flooding levels, he won't know for a while.