Keeping Invasive Species Out

Fish and Lake Management
European Rudd, not to be confused with golden shiner. Notice the red fins. These fish have displaced native minnow species in lakes all along the eastern seaboard.
European Rudd, not to be confused with golden shiner. Notice the red fins. These fish have displaced native minnow species in lakes all along the eastern seaboard.

Editor's Note: This article was stimulated by an email from reader Scott Schillig, owner of Hoosier Pond Pros in Indiana, after he read Cornwells Bucket Biology article in the March-April issue. Schilling emailed asking about the best protocol to clean his equipment as he moves from pond to pond, when he doesn't have three days to wait. We forwarded the email to The Fish Professor; Mark Cornwell, for his response.

In order to do my job as a fisheries professional, I maintain a permit called a License to Collect and Possess. This document allows me to do cool things with my students like electrofishing, seining, and all kinds of netting that is generally not allowed in New York State (NYS). In order to sample fish in my state, I need to have a permit. Period. A few years ago, this permit document doubled in size with an additional three pages. These pages in the new permit were all dedicated to controlling the spread of invasive species in New York inland freshwaters. Cumbersome yes, but also necessary!

First, let's define invasive species. Simply put, it is "A species which is non-native and whose introduction is likely to cause environmental or economic harm," ( Invasive species are a huge problem almost everywhere. Zebra mussels, starry stonewort, hydrilla, curly leaf pondweed, Eurasian watermilfoil, European Rudd, weather loach, round goby, carp, brown trout, alewife, spiny water fleas—the list goes on and on and on. Billions of dollars are lost each year battling problems caused by invasive species. Not good.

Here is an interesting question that I had to ask myself. Have I ever introduced an invasive species? Answer: Yep, and it was totally an accident, as most introductions are. How? Well, four of my five campus bait ponds have been infested with Eurasian watermilfoil. Milfoil spreads mainly by fragmentation, where a piece of a plant can root and grow in a new location. Back in the bad old days, I would run around from pond to pond to pond without cleaning the net. Fragments of milfoil would ride along on my nets as we seined minnows, and then they would fall off the net into the next pond, causing an infestation. This is very common with milfoil, and it is often spread from water to water on boats, motors, trailers, and equipment.

What to do? Keep them out! That's what!

Why? Because you don't know what kind of problem you will have, and it's generally bad. How do you keep them out? Here is a list of a few things to do that will give you better odds of keeping invasive species out of your pond.

  1. When you remove the boat or gear from the water, drain the livewell and the boat. This should be done well up the boat ramp, not near the lake. Water that drains from the boat should not find its way immediately into the lake. That could cause localized spreading of invasive species.
  2. Look around the boat as it comes out of the water. Remove any visible plant material, mud, and other debris from the boat, motor, and trailer. Pull the boat plug and let the boat drain while trailering. Be vigilant about things clinging to the trailer.
  3. If there is a boat wash, wash the boat as it comes out of the lake.
  4. Put some straight bleach in the bilge (bottom) of the boat to slosh around as you trailer the boat. This will kill most things in the bilge.
  5. Dry your boat or gear for three days. Aquatic organisms hate desiccation and heat. Park your boat in the sun, and let it bake for three days. This will kill most big nasties, except certain plant seeds such as water chestnut, which will persist for years, even when dried.
  6. If you cannot dry the boat and gear, then you need a hot water pressure-washer, like a car wash. Pressure-wash the boat and trailer with hot water, or even better, active steam. Keep the plug pulled, and get in the boat. Pressure-wash everything except the electronics. Especially focus on the carpets.
  7. Put a small amount of bleach in the livewell, cycle it, and then drain it. For that matter, keep a spray bottle of bleach to clean surfaces. Don't worry, chlorine in bleach dissipates into the air quickly, and will not remain to hurt the next water body.
  8. If you have nets, pressure-wash those, too. And while you are at it, pressure wash the anchor and rope. After lab, we remove everything from the boat and put everything on the grass or blacktop. We wash the boat, then the trailer, and then the gear. If it touched water, and you can't let it bake for three days in the sun, hit it with high temperature hot water or steam.
  9. Motor a problem? We flush our outboards with chlorinated tap water with a set of rabbit ears that attach to a hose.
  10. Here is one I bet you or someone you know has violated—and this is a HUGE problem— stock the fish, NOT THE FISH WATER! What? When you stock fish in your pond, don't stock the water, too. Net the fish carefully out of the transport tank and allow the net to drain a few seconds, then put the fish in your pond. DO NOT run the water from the transport tank into your pond. If you do this, you now have any invasive species in your pond that the grower has. You want the fish, and nothing else. Have that grower dump their water elsewhere. Maybe in the middle of a field away from surface water.
  11. Along the same lines, don't dump your bait bucket. That's another huge and common problem. Many of the worst introductions have come from intentionally dumping bait. Not good. Entire food webs are changed by invasive species. I have seen it firsthand.
  12. Don't use felt-soled waders. The felt soles hold on to algae that can be moved from water to water as you travel. If you do use felt soles, soak them overnight in a garbage can of very salty water. This will kill most freshwater algae left in the felt.
  13. Soak nets in a chemical disinfectant called VIRKON if the nets must be used quickly in another water body. I would recommend an overnight soak. If zebra mussels are your target though, it may not kill them in a short soak.
  14. If you are in a stream with known invasives, start sampling (or fishing) upstream, and then move down rather than the reverse. Moving downstream will keep you from spreading invasive nasties upstream.
  15. Don't move rocks. Zebra mussels, exotic snails, and other invasives attach to rocks.

Remember: You don't want noxious invasive species in your pond, and we all have an obligation as stewards of our aquatic resources to not spread these nasty things around. Drain it, wash it, disinfect it, and then dry it—every single time, always.

Reprinted with permission from Pond Boss Magazine