ABSTRACT The predation of diving ducks on Dreissena polymorpha was investigated to determine which size of zebra mussels are most commonly preyed upon by waterfowl. The gizzard contents of various species of ducks from Point Pelee Ontario were examined for mussel shell fragments to determine the mussel size consumed. The data was compiled to calculate an average mussel size and the amount of predation on each size by ducks. Waterfowl fed preferentially on zebra mussels of moderate size with a mussel size of 16 mm being optimal. The delicate balance between energy expenditure and consumed food energy along with the threat of kleptoparasitism guide waterfowl to feed upon mussels around 16 mm.
It is also possible that confounding variables such as fish predation have affected size selection by altering the mussel population densities in the hunting habitats. INTRODUCTION Zebra mussels, or Dreissena polymorpha, invaded the Great Lakes in 1985 from European waters. Their rapid spread throughout the lakes is believed to be a consequence of recreational boating and commercial shipping (Johnson and Padilla, 1996).
Zebra mussels’ abilities to attach and proliferate on several types of substrata have increased their numbers tremendously with densities reaching as high as 700 000 mussels per square meter in the most populated areas near power plants (Custer and Custer, 1997).
This has resulted in both unstoppable abiotic and biotic changes (Macisaac, 1996).
The Essay on Invasion Of The Zebra Mussels
Invasion of the Zebra Mussels There has been an incursion into the sovereign territory of the United States of America. The Zebra mussel, an animal much akin to the clam, has colonized nearly every hard surface in the Great Lakes area, and many rivers and streams attached to them. These invaders arrived on ships from England, pumped out through the ballast. Zebra mussels are from a different ...
One of the possible opposing forces for the invasion of Dreissena polymorpha has been the predation by molluscivorous waterfowl. Zebra mussels will attach themselves readily to many submerged substrates including rock, macrophytes, native molluscs, canal and dock walls, water craft and motor outboards (Macisaac, 1996).
Dreissena fouling of water intake pipes is also a noted concern and ongoing problem at various industrial plants along Lake Erie. Macisaac (1996) attributed the dense population of mussels around intake pipes to the number of colonists in the intake current, constant replenishment of food, and the perpetual removal of mussel wastes. A characteristic of zebra mussels is they act as a filter mechanism removing clay, silt, bacteria, phytoplankton, zooplankton, and contaminants from the water, propagating clarity (Macisaac, 1996)..
