Aquatic Invasive Species & Trout Streams It’s Up to All of Us Now

by Dr. Bryan Burroughs, Michigan TU Executive Director

The Great Lakes have been plagued and transformed by aquatic invasive species (AIS) over the last 20-60 years: first by sea lamprey and alewife, and later by dreissenid mussels and gobies, among many others. Not every new invader finds a competitive niche and explodes, but every so often, a new AIS does with transformative impacts to our waters. Over the years, we’ve seen a few of these show up in our trout streams. Sea lamprey spawn in streams, and juveniles are raised there for several years, living in soft sediment bottom areas. Fish passage barriers and chemical treatments are employed to address the sea lamprey, often with costs to the health of coldwater fisheries in those streams. Zebra mussels have been transported into some of the reservoirs on trout streams and seem to find suitable conditions downstream of the dams. Gobies are present in many streams but, thankfully, don’t seem to thrive in healthy, intact, well-functioning coldwater stream systems.

Over the last five years, we’ve seen some new AIS appearing in trout streams, and these more recent invaders seem particularly suited to the conditions. New Zealand mudsnails (NZMS) were first detected in the Pere Marquette River around the flies-only waters and subsequently in other river sections. Shortly afterward, they were seen in portions of the Au Sable and Boardman Rivers, more recently in the Upper Manistee River, and this past year in the Grass River where Shanty Creek joins it. Didymo, or “rock snot,” primarily found in the St. Mary’s River rapids, was discovered in the Upper Manistee River around Christmas 2021. These species appear well adapted to flourishing in trout stream conditions and have exploded to incredible abundances in other places. Now that they have been introduced to these rivers, only time will tell how prolific they become and how great their impact on the fisheries. Currently, there are no well-developed treatments for eradication.

It is difficult to determine with certainty how these AIS were introduced into these streams. Adult NZMS can be no larger than a grain of rice, and didymo, a diatom, is far more challenging to detect. In the future, it may be possible with genetic tools to understand how these AIS found in Michigan rivers are related and to perhaps piece together a picture of where they came from and how they spread. But, for now, anglers are a major vector for spreading these AIS into streams. Regardless of where they came from initially, they are here now, and all of us are the most likely means by which they will continue to spread to new trout streams.

We must all accept the responsibility for preventing their spread. Contemplate for a moment how many anglers have enjoyed our incredible trout fisheries before us; how much effort has gone into repairing and protecting these fisheries so that they continue to be vibrant, amazing angling destinations; and how many future anglers deserve the privilege of enjoying what we have been able to. We find ourselves in a situation where simply moving between two rivers can jeopardize all that.

We all must adapt routines to decontaminate our fishing gear and do so as a habit. Do you share your toothbrush with others? Do you serve food on dirty plates without washing them? We find ourselves with clear and present threats to the future of our trout streams, and we can no

longer afford to move our waders or other equipment from one river to the next without thought.

For some time, these new AIS threats were in a novel phase, and it was difficult to understand what decontamination practices of fishing equipment were effective and feasible. Things have caught up, and now we know. Michigan TU is finishing the publication of a decontamination guidebook for AIS, which should be arriving in mailboxes about the same time as this magazine. The guidebook disseminates the practices that have been proven to work and shares how using them individually or in combination can be crafted to suit your fishing practices feasibly. Please read it, save or share it, and encourage others to pick up a copy at their favorite sporting goods store for free or find it on our website. We will only prevent the spread of AIS to new trout streams if all anglers adopt good practices.

To summarize some of the critical recommendations on decontaminating gear, we offer the following: 1. Always inspect gear after fishing, scrub off any visible debris with a stiff bristle brush, and rinse equipment with water liberally. This should be considered the first line of defense in every situation and can help the most with the least amount of effort. 2. To prevent the transport of New Zealand mudsnails on equipment, it’s possible to use techniques involving drying, freezing, and chemical treatments. One practical and feasible chemical treatment involves liberally and thoroughly spraying waders

and equipment with Formula 409, undiluted from the concentration, bought over the counter from the store. Allow to sit on equipment for 20 minutes, then rinse off with fresh water. 3. Regular household dish detergent (e.g., Dawn) has proven highly effective with liberal rinsing afterward for didymo. Felt sole waders are shown to harbor didymo significantly more than lug soles (porous felt surfaces hold moisture), so avoid using felt soles when possible.

Taking these steps to decontaminate equipment may add some thought and time to your angling activities. Adopting a new practice is somewhat challenging to start before it becomes a routine habit. Nonetheless, these are effective and practical practices and within all of our reach to adopt. The future of trout streams may be in the hands of anglers, preventing AIS from hitchhiking from one river to another. These AIS can significantly impact our fisheries that could overwhelm any positive enhancements we have made to them. Is it worth taking an extra 10 to 20 minutes to help ensure the future of these trout streams?

We all take our preciously limited vacation time to enjoy these places; are we ready to take another few minutes to ensure there are still places our grandchildren and we can enjoy? Make no mistake; this is a call to action. Make 2022 the year you begin routinely decontaminating your equipment for AIS. It’s going to take all of us to ensure our favorite places stay incredible. We can prevent the spread of these invasive species, but it has to start with each of us.