Mussels are almost impossible to eradicate once they've settled in. In my area, the Bleu Massawippi organization is working very hard and is slowly gaining the upper hand over the zebra mussels. However, in the Great Lakes, unfortunately, it's somewhat of a lost cause. Right now, the goal is to reduce new introductions, to stop these species from spreading beyond the Great Lakes and to ensure that they remain only where they're already found.
Each mussel can release a million eggs a year. This amounts to over 100,000 mussels per square metre in some areas. Prevention must be the first step. It's also the most effective way to lower risks and prevent other issues.
Once the situation calls for control measures, costs rise exponentially. Take the Great Lakes, for example. A town has water intakes on Lake Ontario. It costs the municipality over $50,000 a year just to keep mussels out of the water intakes. I have another example. In a municipality in our area, mussels have managed to infiltrate the water treatment plant. The municipality must replace 12 filters in their plant every year, and each filter costs $20,000. The municipality has a population of 2,500.
The most important thing is to prevent contamination and the introduction of these species. To this end, boats must not be transported while their drain plugs are in place. This is one of the easiest ways to prevent contamination. That way, the boat drains and much less contaminated water is transported from one body of water to another.