New Zealand mud snails are harmless

New Zealand mud snails are harmless. These non-native mollusks do no ecological damage. Closure of Capitol Lake because of them is not justified.

That’s contrary to the negative alarmist stories that we’ve heard for the last seven years. Here’s why I believe they’re harmless.

First, I find no published scientific accounts of any ecological damage caused by these snails, anywhere in Washington. Neither does the US Geological Survey, which maintains a web page of non-native aquatic species nationwide. Along with the usual list of possible NZMS’s impacts, the USGS summarizes real damage actually observed in all USA waters in two words; “None Known.”

Second, the snails are “clonal” — feeble genetic weaklings with zero ability to adapt to any hostile feature of Washington waters. Like a native crayfish that seeks, eats, and digests them. The snails have never in all of their long evolutionary history in their isolated island homeland encountered anything like it. And they have zero ability to acquire (by natural selection) evasive behavior, unpalatable taste, thicker shells, or any other defense against this new (to them) ecological horror.

The only thing that clonal organisms can do better than any others is multiply rapidly. By killing the native organisms that control the snails, drawdowns of Capitol Lake probably enable the NZMS’s to rebound to spectacular numbers — until their competitors and predators finally recover.

I expect that the NZMS’s aren’t damaging Capitol Lake. If so, it’s time for DES to re-open it to boating, fishing, and other public access.

This story was originally published January 4, 2017 at 6:11 PM with the headline "New Zealand mud snails are harmless."