Growth Cycle & Toll

The zebra mussel’s reproductive cycle allows for rapid expansion of the population. A mature female can produce up to 40,000 eggs in a cycle and up to one million in a season. Zebra mussels can live as long as five years and have an average life span of about 3.5 years. The adults are typically about the size of a thumbnail but can grow as large as 2 inches in diameter. Colonies can reach densities of 30,000 - 70,000 mussels per square meter.

Edging Out Native Species
Due to their quick life cycle and explosive growth rate, zebra mussels can quickly edge out native mussel species. Negative impacts on native bivalve populations include interference with feeding, habitat, growth, movement and reproduction.

The impact that mussels have on fish populations is not fully understood. However, zebra mussels feed on phytoplankton (algae), which is also a major food source for planktivorous fish, such as bluegill. These fish, in turn, are a food source for piscivorous fish (fish eating fish), such as large-mouth bass and northern pike.

Economic Concerns
In addition to the ecological impacts, there are also many economic concerns. Zebra mussels have caused major problems for industrial complexes located on the Great Lakes and associated bodies of water. Mussels can clog water intakes of power plants, public water supplies and other industrial facilities. This can reduce water flow (by as much as two-thirds) to heat exchangers, condensers, fire fighting equipment and air conditioning systems.

A Michigan-based paper company recently reported that it had spent 1.4 million dollars in removing only 400 cubic yards of zebra mussels. There is currently no widespread/whole lake control practice that would be effective without harming other wildlife, and there does not currently appear to be an effective predator of the mussel.