Earlier this week Minnesota Public Radio highlighted a natural resources success story, the fight to control the sea lamprey in Lake Superior.
The lamprey is a disgusting parasite of a fish, an eel-like beast with a round, tooth-filled mouth designed to latch on to other fish, and a rasping tongue that bores a hole into the host fish's flesh so the lamprey can suck fluids from the host. They migrated from the Atlantic to the Great Lakes via a canal around Niagara Falls, showing up in 1939 and nearly wiping out the lake trout population in the Great Lakes.
In the 1950s a chemical was found that kills their spawn, and they are easily trapped by low dams that other fish can swim over to find spawning grounds. Today about 90 percent of the lamprey in Lake Superior are killed each year, keeping them in check and allowing the lake trout population to grow.
This is a great story, but it points out the problems with invasive species. Once they get in, they can be devilishly hard to control, let alone eliminate. Another news item this week was the explosion of eurasian milfoil in Minneapolis lakes due to the warm spring. Here's an invasive species that, once it is established in our waters, is hard to control. Zebra mussels are also hard to get rid of once they get in, which is why the state is pushing boaters to check their boats before moving to another lake.
Minnesota is watching the encroachment of the asian carp species that are getting nearer in neighboring states and starting to show up in state rivers. The state needs to work hard to keep them out. They are easier to keep out than to control.