Consultant's Report - Minnesota State Legislature

MINNESOTA DEPARTMENT OF NATURAL RESOURCES
Feasibility Study to Limit the Spread ofZebra Mussels from Ossawinnamakee Lal{e
Treatment Alternative Recommendations
Treatment Locations
Limiting the downstream movement ofzebra mussels could occur at several locations, including
areas of Muskie Bay and possibly Pelican Brook. While similar treatment alternatives may be
applied to each system, the physical implementation of the alternatives differs greatly. For
example, the hydrologic characteristics of Muskie Bay with its slow moving water provides
ample contact time for exposure to many of the .chemical treatment alternatives. In contrast, the
lacustrine enviromnent ofthe bay may present physical implementation obstacles due to the size
and volume of the treatment area. Conversely, the more riverine areas of the system (Le., near
the outlet structure downstream ofMuskie Bay and Pelican Brook) present other implementation
and contacting issues due to the continuous volume ofmoving water.
Given the wide variety of characteristics within the system (i.e., various water depths and flow
velocities), two general treatment locations are most likely advantageous for the limit of zebra
mussel veligers from Ossawinnamakee Lake. Since the main goal ofthe project was to limit the
spread of zebra mussels from Ossawinnamakee Lake, the lake represents the primary treatment
location. Within the lake, some type ofbarrier or deterrent may be feasible at the exit ofMuskie
Bay, as this area is constricted by width. In addition, chemical treatment alternatives could be
applied in the greater portion of the bay, as seen in previous treatments. It is likely that two
treatment alternatives working concurrently would result in the greatest efficacy to confine the
current zebra mussel population and reduce downstream dispersal. These alternatives are
described in further detail below.
Based on the observed field accounts outlined above, the lmown life histories of the organism,
and the accounts in the literature of environments and locations of where the organisms are
typically found, it is likely that the hydrologic characteristics of Pelican Brook (Le., shallow
water with high flow velocities) may provide a natural defense that is not conducive for zebra
mussel populations to become established. In addition, many of the treatment alternatives are
not feasible in high-flow applications, such as the brook. However, a contingency plan is
recommended and should be developed in the event that sampling events identify areas of
established populations in the brook. This plan could outline the steps necessary to target
eradication of adults in Pelican Brook when discovered. Several point application alternatives
could be employed from Table VI-t.
Treatment Objectives
As stated previously, the primary goal of this evaluation was to provide an analysis of the
effectiveness of potential technologies in preventing or limiting the in-water transport of zebra
mussels, particularly the veliger stage, in the outlet stream of Ossawinnamakee Lake. For the
purposes of discussion and general treatment application, two distinct control categories have
been developed. These are dispersal control and population control. Dispersal Control is
defined as limiting downstream movement of any or all zebra mussel life stages. Population
VI-lO Alternatives Analysis and Recommendations