Mystery of the Month – September

A multiple choice quiz for your mystery this month.  The photo above is showing:

a.  A climbing structure at a third rate water park.

b.  A structure that helps strain trash out of the creek.

c. A structure to slow down the creek to help prevent erosion.

d. A barrier to stop carp from moving upstream.

e. None of the above.

The correct answer is d. A barrier to stop carp from moving upstream.

This cattle grate carp barrier is in Kohlman Creek, just upstream of Kohlman Lake. It is there to prevent this invasive fish from swimming upstream to Kohlman Basin, a breeding ground for carp. The barrier is raised out of the water in the winter but early spring when carp start looking for a place to breed, it’s lowered down to keep them out. As stated in a previous Ripple Effect, female carp can lay between 100,000 and 500,000 eggs at one time, and they hatch in less than a week. Then when the adult carp get older they root up shallow plants and muddy the water. This increases phosphorus which increases algae. In preventing carp from moving upstream, we are helping to improve water quality in the Phalen Chain of Lakes.

U of MN carp wranglers, Justine and Reid harvesting carp during the spring migration.  Carp were trapped between the barrier and a net.  They were so crowded most could be removed by hand.  For more about Justine and Reid’s adventures with the carp research project, look for the keyword “carp” in the blog margin.

The cattle grate has to be cleaned often, especially after large storms.