Invasive Aquatic Species - Why Should We Care?

By Jeff Dillon, Regional Fisheries Manager, Southwest Region Most Idahoans who spend time in the outdoors are familiar with issues surrounding non-native and invasive species. We often hear about noxious weeds and how they affect wildlife habitat. Cheatgrass, star thistle, spotted knapweed, and rush skeletonweed are just a few of the many non-native and invasive plants you may have heard about in southern Idaho. These plants outcompete native plants, and can have a real impact on food resources for deer, elk, and other wildlife. But what about non-native aquatic invaders? For the most part, they are out of sight, out of mind. But undesirable aquatic plants and animals can have a dramatic affect on your fishing and boating opportunities. Think about these examples. Whirling disease is caused by a European organism unintentionally imported to the U.S., and in some cases it has had a major impact on western wild trout populations. New Zealand mudsnails are well established in much of the Snake River, and a few years ago showed up in Silver Creek. They are so prolific they can replace native snails and crowd out aquatic insects though we don't yet know what effect they'll have on fish populations. And Eurasian water milfoil, now common in northern and southwest Idaho, is a non-native aquatic plant that can quickly cover the entire surface of smaller lakes and ponds, making fishing and boating impossible. Invasive aquatic species might also include undesirable fish, crayfish, bullfrogs, other nuisance plants, and even other disease organisms. Illegal or unintentional fish introductions commonly impact established fisheries and are very expensive to control. Illegal perch introductions in Lost Valley and Horsethief reservoirs, for example, provide poor fishing for small fish, and overabundant perch also compete with trout and slow their growth. In this case the only real fix is to treat the reservoirs with chemicals to kill all the fish, and then start over. Such treatments can cost tens of thousands of dollars or more. Eurasian water milfoil is becoming more common, especially in northern Idaho lakes and southwest Idaho ponds. Locally, the Caldwell Rotary, Duff Lane, Horseshoe Bend, Sawyers, and Airport Ponds were infested with milfoil and pretty much useless to fishermen. Milfoil can spread easily, and new infestations can come from one small stem transported on a duck's foot, boat trailer, or float tube. Within a few years, milfoil can crowd out other aquatic plants and cover the entire surface of smaller ponds. We've worked with local counties and other entities to chemically control this nuisance weed. The treatments seem to be effective, and fishing has improved in these ponds. But it's like mowing the lawn. We expect milfoil to come back and require treatment every two or three years. It's a commitment of our time (and your money) that wasn't around before milfoil showed up. So, what can you do to fight these aquatic invaders? First and foremost, you can educate yourself and your fishing and boating friends. Learn to identify milfoil and other invasive aquatic weeds. Make a practice of thoroughly cleaning vegetation from your fishing gear, boat, and trailer before moving from one body of water to another. Take extra precautions with waders and felt-soled boots that can harbor whirling disease spores and mudsnails. And never practice armchair fish management. While it may seem a good idea to transport and stock fish into your favorite pond or lake, it's illegal to do so and you might do more harm than good. Learn more about aquatic invasive species and how you can prevent their spread at www.protectyourwaters.net.