Thursday, November 10, 2016

Big Yellow Excavators Improve Local Fishery

By Bill Bartodziej


How can big yellow excavators improve a local fishery and create a safeguard against carp in the Phalen Chain of Lakes?

Let’s back up before we answer this question.

Markham Pond is at the headwaters of the Phalen Chain of Lakes and drains into Kohlman Creek, which feeds Lake Kohlman. About six years ago, Markham Pond was identified as a carp nursery area. Thousands of carp, young and old, had the ability to migrate down into and infest the main lakes in the Phalen Chain. Carp are bottom feeders that stir up sediments, release nutrients and can negatively impact water quality. 

Markham Pond is a shallow system, with a maximum depth of four feet. During harsh winters, it’s likely that game fish species, like bluegill sunfish and largemouth bass, froze out and died. However, carp are a very resilient species and can handle winter conditions in shallow lakes and ponds.

Over the last couple of winters, Markham Pond was drawn down (or drained) in order to manage the carp population. This year, summer sampling in the pond revealed a few native fish species, like minnows, green sunfish, and bullhead, but no common carp. 
We took that as a sign that we were successful in significantly reducing carp and eliminating this threat to the Phalen Chain of Lakes.

University of Minnesota Carp Research Team
netting carp on Markham Pond
So the bad guys that threaten water quality are gone, end of story, right?

Wrong. Carp are stealthy and reproduce like crazy, and have to potential to explode in Markham again. What can we do to naturally control carp in Markham? The surprising solution was actually discovered in our watershed by the University of Minnesota’s Carp Research Team; bluegill sunfish zealously consume carp eggs, acting as a biological control mechanism. Carp have a very difficult time successfully reproducing in lake and pond systems with high bluegill populations. Thus, reintroducing a healthy bluegill population in Markham Pond will create a safeguard against the re-establishment of a substantial carp population.  
Bluegill's appetite for carp eggs should keep the carp population in check.

So how do we improve habitat for bluegill sunfish and other game fish in Markham Pond and help them survive the winter? A reasonable approach is to create a deep water refuge by excavating a wide and deep hole for game fish to hunker down in during the cold months. This fall the watershed is in the process of drawing down the pond by opening up a water control structure. A dry pond bottom will make it easier for excavators and earth moving equipment to do their work this winter.

The Plan
Pond levels are down as we intentionally lower
the lake level in anticipation of construction.

During January and February, we plan to remove accumulated sediment that has washed into the pond and create a fourteen foot deep refuge almost an acre in size. A grant from the Minnesota Pollution Control Agency will help support this work. The paved parking lot at the north end of Hazelwood Park will be used as the construction site entrance and equipment staging area.

Next spring, the pond will be filled back up again and the watershed will work with the DNR to stock game fish species. This deeper refuge area will not freeze to the bottom, even during harsh winters, and will have suitable dissolved oxygen levels for game fish.

Additional benefits of the project will include increased recreational fishing opportunities, robust aquatic plant growth, enhancement of wildlife habitat, reduced pond bottom re-suspension from carp activities and, hence, improved water quality in Markham Pond and downstream waters in the Phalen Chain of Lakes.

So when you drive by Markham Pond this winter and see big yellow backhoes digging away, be assured that this work will help to improve our fisheries and preserve the water quality in the Phalen Chain of Lakes.


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