Tiny Snails Big Issues

Nick M., profile photo

This week’s blog is a guest post by Nick M., a Bucktails alumni. Nick is a civil engineer graduate from Penn State University. He has a passionate interest in aquatic macroinvertebrates and is the co-author of two publications on expanding the range of the New Zealand mud snail in Pennsylvania. Nick has returned to field school in recent years as a volunteer and field school photographer.

When I was a WLA student back in 2014, the New Zealand mud snail was only just beginning to appear in Pennsylvania. Only two bodies of water were known to be infected and they were Lake Erie and Spring Creek, Centre County. Today, the non native snail has been observed in nine counties and has likely gone undetected in many others, possibly including your own!

What’s wrong with the New Zealand mud snail? The New Zealand mud snail is an invasive species. An invasive species is defined as a non-native species that negatively impacts the economy, environment, or public health. In the case of the New Zealand mud snail, it has a notable effect on the environment by reproducing asexually and outcompeting the native organisms that inhabit our trout streams. Entire rocks and logs can be covered with thousands of these tiny snails, dominating microhabitats required for other species and depleting their food sources.

Identifying New Zealand mud snail. Thankfully, PA does not have many aquatic snail species that can be confused for New Zealand mud snails. They are 6mm in length with an elongated conical shell, composed of about six or seven whorls. Examples of similar species include the Henscomb hydrobe, slender walker snail, and watercress snail. In the 2022 range expansion of the New Zealand mud snail study with Fish and Boat, we differentiated New Zealand mud snail from these similar looking species by dissecting them and looking for the presence of developing snails because, fun fact, the New Zealand mud snail, unlike our native species, reproduces through live birth rather than through egg masses.

While the reader may not be able to dissect snails at home they can still make a difference! Any aquatic snail about 6mm in length with an elongated conical shell should be reported because the previously mentioned aquatic snails that are not New Zealand Mud snail are considered to be imperiled species in the state of PA. Their records are just as important so please share your observations! You can make a difference by photographing any aquatic snails with conical shells you find and reporting them to either iNaturalist, iMapInvasives, or the USGS invasive species portal. These organizations also provide maps of the New Zealand mud snail’s current distribution. If you fish in or near waters inhabited by the New Zealand mud snail, you can also make a difference by being mindful of keeping your waders and fishing gear clear of debris that may transport this invasive snail to new waters!

The photos used in this blog belong to the author.