New Zealand Mud Snails documented in the Au Sable River

New Zealand Mud Snails Documented In The Au Sable River



New Zealand Mud snails have been discovered in the East Branch of the Au Sable River, just downstream of the Harrietta Hills Trout Farm – Grayling. These invasive snails can move throughout a system and damage the fishery.

On June 6, 2016 a regional EPA lab confirmed that the snails discovered were indeed New Zealand Mud Snails. Representatives from Anglers of the Au Sable and Mason-Griffith Founders Chapter of TU will assist Dr. Mark Luttenton of Grand Valley State University, who first found the snails during routine sediment sampling, in immediately conducting additional sampling to determine if mud snails are found in any other locations of the upper Au Sable River system.

What should anglers do?

The section of river downstream of the fish farm to the confluence with the mainstem Au Sable is now confirmed infected. We encourage anglers and others to avoid fishing or wading in this section of river. 

All anglers fishing anywhere in the Au Sable or nearby rivers, should take great care to prevent the spread of this invasive species.

  • Gear should be thoroughly cleaned and disinfected between uses.
  • Use a stiff brush to remove visible snails from wading shoes and waders, boats, anchors, ropes, and landing nets. Ensure that all mud and debris is removed. Take care to clean around gravel guards on waders.
  • Several chemicals have been found effective for killing these snails. One is full strength Formula 409 cleaner. Equipment should be soaked in this solution for a minimum of 10 minutes, then thoroughly rinsed with clean water and allowed to dry.
  • Snails can live for many days out of water so inspect wading boots inside and out thoroughly after cleaning.
  • It may also be time to reconsider using felt soles. They can pick up and hold more snails and are more difficult to clean and disinfect effectively.

If we all follow these simple precautions we may be able to help stop or at least slow the progression of this invasive species.

Mud snail identification

The New Zealand Mud snails are small, up to 1/8” in length (up to 50 can fit on the face of a dime). They range from light brown to black in color; have 5-6 whorls, of gradually increasing size from one end to the other, and are right-handed snails (meaning when held with the small tip upward, the opening should face you to your right side).  They reproduce prolifically and can reproduce asexually meaning a single specimen can result in thousands of offspring.


If you think you have found a New Zealand Mud Snail contact:

Seth Herbst, DNR Aquatic Invasive Species Coordinator

Bill Keiper, DEQ Aquatic Invasive Species Biologist