It's been a rough summer; I could be complaining about the weather, but that matter is trivial in comparison to the recent reports showing that aquatic invaders, commonly grouped under the term Aquatic Nuisance Species (ANS), continue to forge ahead into new territories. Month by month this summer, new lakes and streams are being added to a list of infested waters that are subject to these invasive species despite heightened campaigns by state and federal wildlife agencies alerting sportsmen of the increased threat of ANS in the upper Midwest.
My Lake Has Fleas
My first interaction with one of the more publicized ANS creatures happened this year on Lake of the Woods, a popular destination for many anglers due to its proximity to Fargo and Grand Forks, and all of northern Minnesota. While fishing walleyes there with my wife's cousin, he pointed out a yellow glob forming on the Fireline where it intersected the water's surface.
"Those are spiny water fleas," he remarked, "we didn't have them here until about two years ago" he continued, stating the local suspicion is that the small crustaceans were transported to the lake in the bilge or livewell water of recreational angling vessels. As I reeled the line up to inspect the mass, I saw a gooey mass with little stickers poking out and dozens of tiny black dotted heads.
Each flea is about a half-inch in length with a large spine that makes up most of its profile. They originated in Russian and European waters and were introduced first into Lake Huron and soon after into the remaining Great Lakes through the untreated ballast water of shipping vessels. From there, the species has traveled in the water of recreational craft, on fishing line and in minnow buckets to many lakes within a day's drive of the Great Lakes and points even further away. What's more, even after their eggs have dried out, they can become viable again with just a bit of water, preserving a future generation for distant waters. The species can reproduce asexually, meaning one flea is enough to colonize a water.
Recent studies suggest that due to the spiny water flea's hardiness, ability to quickly reproduce and its voracious appetite for zooplankton, entire base species of those zooplankton in a body of water can be decimated, impacting the very foundation of food pyramids which sustain popular sport fisheries. Furthermore, the spine on their bodies renders them inedible to many small fish, further decreasing their value to an ecosystem.
A Tangled Mess
Recently, Eurasian water milfoil was found near a public access on Lake Florida near Spicer, Minn. This marked the 213th of the state's lakes to be infested with the plant that is well known for taking over waters in a matter of seasons. Like the water flea, Eurasian water milfoil is most often transported in the water of recreational and fishing boats and is found across the lower 48 states of the Union, except for Utah and Wyoming.
Most plants require a solid rooting to take hold in an ecosystem. That is not the case with Eurasian water milfoil, which needs only a stem to start a new plant. Roots and leaves quickly grow from just an inch of green stalk and over a few summers can create one of the most unsightly beds of vegetation found in this region.
Large, tangled mats of densely packed milfoil choke out native vegetation by August in lakes where it is well established and render that area of water devoid of suitable habitat for a variety of native species. The presence of this nuisance species restricts anglers by limiting fishable waters and by causing low oxygen levels in some lakes as it decays in the winter.
The battle with Eurasian water milfoil is well documented in Ransom County, N.D. at a popular, isolated bass and panfish lake known as Dead Colt Creek. It was discovered in 2005 that the small reservoir contained a significant amount of Eurasian water milfoil and the battle to eradicate the invader, while trying to save the fishery and native water plants began. Through water drawdowns to kill the plant by drying along with winter drawdowns in hopes of freezing the plant, the North Dakota Game and Fish Department has been combating the stubborn trespasser for nearly five years. However, once nuisance species become established in a water body, the battle is pretty much lost.
The only way to win the battle against ANS is to prevent their spread to other water bodies. State legislatures across the country have passed laws requiring anglers, hunters and boaters to clean their craft of all vegetation and drain their livewells and bilge areas of water before transport. Failure to do so in some jurisdictions, including Minnesota, can result in fines against the owner who failed to remove vegetation, mud and water from a boat or boat trailer.
In order to get the word out, agencies have stepped up their public campaigns against ANS. This is evidenced by the billboards along popular fishing highways, like Highway 10 in Western Minnesota and Highway 53, leading up from Lake Superior to the Boundary Waters in Northeastern Minnesota. Stickers and displays at gas stations also alert anglers to their responsibilities to keep boats and equipment free from these invaders. Many states have also implemented launch checks, where agents help anglers inspect boats and encourage routine examinations for ANS-carriers like mud and plant matter each time boats are taken out of the water.
Agencies like the Minnesota DNR and North Dakota Game and Fish Department provide pamphlets and stickers requesting anglers to let their boats dry completely inside and out for five days before traveling to fish a new lake. If such a wait is not possible, the boat should be pressure sprayed with warm water, or washed with a bleach and water mixture.
Despite recent setbacks, the battle against ANS wages on. Through assistance from anglers, hunters and boaters, the hope is that these species can be prevented from entering and impacting new waters, and each lake and river that remains without them is a victory...in our outdoors.