That would be kinda like the Zebra Mussel problem we have here in the great lakes. They were introduced into our water in the bildge,and ballast tanks of freighters. Very much UNWANTED. The upside to the problem is that the water clarity in lake Michigan is better than it ever has been. Hard to believe that a body of water as large as this can be affected by a clam shell the size of your pinkey finger nail. Sorry for getting off subject,But an interesting subject that just popped into my head........STEVE