After winter fish kill, how will Lake Christina respond?
Lake Christina in western Douglas County is considered one of the more important waterfowl lakes in Minnesota, and efforts continue to try to manage it for those purposes.
The Minnesota Department of Natural Resources lowered the water levels 18 inches last fall through the lake's permanent pump structure, which has been in place since 2012. The hope was that lower water levels would lead to more winter kill of fish in the lake. At least to an extent, that seems to be what has happened.
"I think we were encouraged to see some dead fish out there," DNR wildlife lakes specialist Nick Brown said. "That was our first goal. When we lower water, one hope is to induce that winter fish kill, which we saw at least some of."
Brown cautioned that exactly what that will mean for the overall health of the lake this year remains to be seen. Water levels on Christina are right back up to where they were before the drawdown last fall after plenty of moisture through winter and into spring.
Much of the fish population on Lake Christina consists of rough fish such as carp, buffalo or bullheads. Those species made up a lot of the fish found floating on the water's surface after the thaw this spring.
Rough fish are predominantly bottom feeders that stir up the sediments and uproot aquatic plants. It leads to turbid water conditions, which in turn can choke out regrowth of plant life.
The DNR had hoped that eliminating some of those fish would be coupled with continued low water levels to allow even more sunlight to reach the lake's bottom to generate plant growth. How well those aquatic plants grow as a result of any fish kill won't be known until mid-summer.
"It would have been nice to see those water levels stay lower, but it's really out of our control," Brown said. "We've got to hope for the best. Up until about the mid 1930s, Lake Christina was a lot lower and fish kill was a lot more common. Since then, there's been a weir installed at the outlet of Lake Christina and at the outlet of Pelican Lake, so the water levels are higher as a result of man-made activities."
Lake Christina has 17.84 miles of shoreline with 3,971.17 littoral acres (area less than 15 feet deep). A very small portion of the lake has a listed maximum depth of 14 feet, but the mean depth is 4.5 feet. It is one of the largest migratory stopover lakes for waterfowl in all of Minnesota, which makes it so important for those species, but also trickier to manage.
"One issue with Lake Christina is it's so big, and so long, particularly east to west," Brown said. "The lake has a lot of wind-driven action, so even when fish are low and plants are good, we can see turbid water out there simply from the wind stirring up those sediments."
Brown also said that winter fish kills are less common today, due to higher water levels, but also milder winters.
"The changes in the climate are leading to on average milder winters, so we see less winter kill from that angle, as well," Brown said. "We've had drawdowns in the past and then had really mild winters and had effectively no winter kill from that, so we actually got pretty lucky this year to see the winter kill that we did."
At its best, Christina has produced vast aquatic plant growth, specifically patches of sago pondweed that waterfowl love to feed on. Canvasbacks in particular have used Christina as an important stopover to feed on the tubers of the sago pondweed during their annual migration.
"Historically, Christina would see 20 percent or more of the continental canvasback population at one time," Brown said. "That's kind of a big deal, especially for a duck like the canvasback, which is historically not very numerous to begin with. We typically see canvasback numbers around 500,000 or 600,000 throughout the continent. There have been counts of 250,000 on the lake at any one point."
Those numbers have not been seen in many years, but Brown said the effort put into Christina is worth it to try to make it as productive of a lake as possible for waterfowl.
"It's a manage-and-adapt kind of system now," Brown said. "It's not a restore and walk away type thing. It's a situation now where we manage, we look at what the result was, adapt, go back and change what we need to and try again. We may never get it figured out, but we can always keep trying. The infrastructure is in place now where we can keep going with the drawdown, try to fine tune to fit the lake itself."