Consultant's Report - Minnesota State Legislature

Habitat Distribution
MINNESOTA DEPARTMENT OF NATURAL RESOURCES
Feasibility Study to Limit the Spread of Zebra Mussels from Ossawinnamakee Lake
Fraleigh et al. (1993) reported that wind driven currents can affect the vertical distribution of
veligers throughout the water column and found that 95 percent of the veligers were encountered
at depths varying from 2 to 6 meters (6.6 to 19.7 feet). Similarly, Mackie et al. (1989) found
veliger abundance at depths from 3 to 7 meters (9.8 to 23 feet). Within temperate lakes, few
veligers were found to occur below the thermocline (Mackie et al. 1989, Fraleigh et al. 1993).
Predators
The zebra mussel veligers have been consumed by crustacean zooplankton and larval fish;
however, the relative importance of this prey on the mortality of veligers is unknown. The
predation ofjuvenile and adult zebra mussels has been observed by crayfish, fish, and waterfowl
(Mackie et al. 1989).
Fishes observed or expected to consume zebra mussels include: freshwater drum (Aplodinotus
grunniens) , redear sunfish (Lepomis microlophus) , pumpkinseed (L. gibbosus) , copper
(Moxostoma hubbsi) and river (M carinatum) redhorse, common carp (Cyprinus carpio), and
blue catfish (Ictalurus furcatus) (MacIsaac 1996, Magoulick and Lewis 2002). Furthermore,
adult zebra mussels have also been found in the digestive tracts of other fishes in the Great Lakes
including yellow perch (Perea flavescens) , white perch (Morone americana), walleye
(Stizostedion vitreum), white bass (Morone chrysops), lake whitefish (Coregonus clupeaformis),
lake sturgeon (Acipenser fulvescens), and the round goby (Neogobius melanostomus) (French
1993). In general, while fish prey on the mussels, it appears that fish do not limit the densities of
zebra mussels (Mackie and Schloesser 1996).
Diving waterfowl are important zebra mussel predators in North America. The following species
have been observed feeding extensively on zebra mussels in Ontario and throughout the Lake
Erie region: greater scaup (Aythya marila) , lesser scaup (A. afjinis) , common goldeneye
(Bucephala clangula), and the bufflehead (B. albeola) (Wormington and Leach 1992, Hamilton
et al. 1994). While bay diving ducks have been known to consume as much as the 57 percent of
autu,mnal biomass of zebra mussels in Lake Erie and 90 percent winter zebra mussel biomass in
Lake Constance, these reported predation events had little impact on mussel biomass the
following spring. The regulation of zebra mussel biomass and abundance by waterfowl is
unlikely in central North America because predation is limited to ice-off periods (Cleven and
Frenzel 1993, Hamilton et al. 1994).
Productivity
Compared to European populations, the densities of zebra mussel veligers and adults in the Great
Lakes are prolific and are among the highest reported to date (Mackie and Schloesser 1996).
Leach (1993) found that Lake Erie averaged 126-268 veligers per liter, whereas the European
waters averaged 10-100 veligers per liter (Fraleigh et al. 1993). Mean adult densities in Lake
Erie ranged from 54,000 (Dermott et al. 1993) to 779,000 (Pathy and Mackie 1993) per square
IV-5 Review ofZebra Mussel (Dreissella pO[ylllorpha) Species