Marsh Lake is shallow with highly organic sediments. In winters with heavy snowfall, organic
sediments deplete oxygen under the ice to the point where fish can no longer
survive (winter fish kill). After a
winter fish kill, carp breed in Rice Marsh Lake in conditions where there is
little predation of carp eggs, larvae, and fry.
The University of Minnesota has discovered that these are the only
conditions in which carp can successfully breed and recruit. If there is no winter fish kill in Rice Marsh
Lake, carp eggs, larvae, and fry cannot escape predation. Therefore, prevention
of winter fish kill is essential to keep carp populations down in Lake Susan
and throughout the Riley Creek watershed.
Aeration or oxygenation of the lake water is the most direct way to
prevent winter fish kill. The District installed an aeration system in
Rice Marsh Lake in October 2010.
system has been shut off in accordance with the current scope and budget for
this project. The system will be turned
on again just prior to ice-on conditions (October 2012 is targeted). Oxygen and water quality levels at various
locations within Rice Marsh Lake continue to be monitored by the Engineer and
by the University.