Zebra mussel has had many effects on the Great Lakes because of its biology. One of the biggest negative impacts it has on recreation is:

1. It has provided an abundant food source for freshwater drum, which exclude sport fish.

2. It has increased water clarity, improving conditions for swimming and diving.

3. It increases the business of boat shops because boat owners pay for the expense of removing the mussels from the hulls of sport boats.

4. The shells of dead zebra mussels accumulate on shore, reducing the quality of swimming beaches.