Are there INVADERS in your lake?
Yes, there are living things in Lake of the Woods, the Winnipeg River and other small lakes near us that were never here before and come from a long way away.
We call these aliens -“invasive species” – these can be fish, plants or small, microscopic animals that move into a new ecosystem and make a new home where they don’t belong.
That might not sound so bad, but with no natural predators (nothing that can eat them, because they are new to the area), invasive species can quickly spread through a new ecosystem.
Once they’ve moved in, these invaders often cause problems for the native species that already live there.
Invasive species can take away habitat, food and spawning sites from native species, driving native species to move away or even die off completely.
A plant or animal that is “native” to an area means that it has ALWAYS been here… it didn’t get moved here or transplanted by someone from another place – it is here because the soil, climate, water and other conditions are just right for it to thrive.
We have rusty crayfish in Lake of the Woods and in the Winnipeg River and, boy, these guys are HUNGRY!
Rusty crayfish can eat twice as much food as the native crayfish (the ones that were here first; the native crayfish are smaller and more pale).
Rusty’s have a huge appetite and love to eat plants that grow under water. This isn’t good, because when they eat these plants, they are destroying the homes of small bugs and fish that live in the lake.
They also like to eat mayflies, stoneflies, midges, and side-swimmers. On top of that, for dessert, they love to eat young fish and fish eggs!
Rusty crayfish are bullies too! They will chase native crayfish out of their favourite daytime hiding locations.
Then, those native fish are more visible to birds and bigger fish, so they can get eaten by them. Rusty crayfish aren’t scared of big fish either – instead of swimming away from them, they’ll attack them with their claws!
How do invasive species get here?
Many people have not realized the impact of some of their decisions on our environment – for example, some people put new fish into lakes on purpose to help make the local fishing better. Some fish have escaped from fish farms and hatcheries. Some are dumped into the nearest lake with the contents of an aquarium or a bait bucket.
They hop a ride on Big Ships!
Large ships on the oceans pump water into their bilge tanks to make them heavier and more stable.
When water is pumped into the tanks in one ocean port, tiny bugs and plants or even fish are pumped in too!
These species survive in the tanks until the ships have crossed the ocean and then arrive in another port (often in another COUNTRY!) where the water from the bilge tanks is dumped out.
These invaders come from all around the world and settle here in Canada or in the United States. Many of our lakes and streams are connected between the two countries and we share the only shipping route from the ocean to the five Great Lakes – the St. Lawrence River!
Check out a map and see how close the St. Lawrence River really is to us!
Some of these fish and other species will make their way into other lakes and streams by swimming there OR catching a free ride on someone’s boat, motor or in their bilge tank… read on!
They hop a ride on small boats, too!
Boats as small as canoes can also transport species from one ecosystem to another.
Do you have a boat?
Have you ever used it in one lake and then moved it to another?
Lots of things can stick to the bottom of your boat and when you put it into another lake without washing and drying it first, those tiny cling-ons (animals, plants) move too!
The animals will drop off the boat when it goes back into the water – but now they’re somewhere they shouldn’t be! Zebra mussels are just down the road in Lake Superior, so don’t let them hitch a ride on your boat!
Tell your parents to WASH and DRY (IN THE SUN) the boat before putting it back into another lake.
Boats with propellers also move species from one place to another. Plants can get tangled in propellers and if they are not removed before the boat is put into another water body, the plants and their seeds will be moved too.
Think about this – it is only a six hour drive from Lake Superior to Lake of the Woods – if you use your boat in Lake Superior and an invasive species hooks on for a free ride, his new home will be Lake of the Woods if you put your boat in without washing it first.
It only takes ONE invasive species to create a whole new population in a new lake.
Another way invasive species can be transferred from one place to another is by dumping live fishing bait overboard. Baitfish are not often the same species as those found in the lake or river you are fishing in.
These small baitfish will want the same food and space that the fish already in the lake also want.
Unwanted aquarium pets are another source of invasive species. When people dump their aquariums into the lake or river, the turtles, fish, snails, and even plants may continue to live and reproduce. These invasives compete with native species and may even eat them!