Madison River
New Zealand Mud Snails in Madison

Mud snails in the Madison River probably came over on a fisherman’s waders, picked up in the mud of New Zealand. The snails are very tiny and highly reproductive. The problem is created by their high numbers—billions of them—soon they cover every stone, log or other object in the water. In the process they will consume all the algae that other, more desirable trout stream invertebrates need to survive, including mayflies, stone flies and caddis flies which are vital parts of the food chain. A collapse of the food chain will result in a collapse of the fishery, plus the mink and otter that depend on the fish for food.

At this time there is no method to stop the spread of this invasive non-native. It is likely that the New Zealand mud snail will continue to infect more streams due to the popularity of wade-fishing in streams. It is not unlike what happened to the Great Lakes fishery when the St. Lawrence Seaway was developed after WWII, and sea-going ships were allowed to dump the water they had picked up in Singapore harbor from their ballast tanks into the far western reaches of the Great Lakes. Of course, the illegal introduction of Lake trout in Yellowstone Lake is another example of non-native invasion of an undesirable species. ~