Invasive Species

Invasive Species
By:
William Aamodt

Increased annual water temperatures, increased aquatic vegetation area, and decreased native species. These are all signs that invasive species have taken control of your lake. Invasive species have been flying under the radar for a long time in this country and were left unadulterated for many years. Only when they start to cause a problem do we take notice and realize that we need to do something about it. Increased water temperatures are happening due to zebra mussels, these mussels can siphon more water through their bodies to locate food than most of the native mussels to this region. This siphoning cleans up the water, sure that’s good for swimmers and recreational boat users, but what it does is allows more light to reach deeper into lakes. Deeper in the water means that more water is warmed up, increasing water temperatures. This could lead to some major perchid (walleye and perch) lakes turning into centrachid (bass and sunfish) dominated lakes. It also means that some deeper areas are going to be inhabitable by aquatic plants that were prior contained in shallower areas.
Its not just mussels that have been invading our waters; there are plants too. Eurasian water milfoil has become a problem in many lakes. Unlike its native cousin, Northern water milfoil, Eurasian is highly transportable. If it is broken into little pieces, say by a weed harvester, each one of those pieces is able to become an entire new plant! It is found in dense patches that can blot out any sunlight from reaching the lower depths of a lake and thus eliminating more oxygen from the system. Not only is it highly movable, it is highly adaptable. It has been choking out native aquatic plants since it was transported here from its native home range.
Another tiny little aquatic invertebrate that is causing some trouble is the Spiny Water Flea. This little guy is a voracious predator that can eat all of the other invertebrate food, usually phytoplankton or zooplankton, before the native species can. The reason that this is bad is because it causes problems with fish. The species is named spiny because its tail is basically a large spine that, when ingested by predators, fish, tends to puncture holes in internal organs. Fish tend to learn to stay away from things that hurt and thus this species goes unchecked once it has established itself.
The only reason that these pests are here is because of humans. Just like any other exotic species, they have been transported by the bipedal species that drives boats from one lake to the next. A plant just can’t sprout wings and decide it wants to fly over the ocean to grow in a new lake; it had to get here somehow. The same goes for every invasive. They cause problems in the new systems because they go unchecked. When something enters into a new system, it usually leaves its old predator behind, meaning that there is nothing eating or utilizing it. This leads to exponential growth that will only yield once all of the usable resources are gone.