Sea lampreys are an excellent example of an invasive species.
They spread like wildfire from lake to lake, wreaking havoc on indigenous cultures. This unexpected attack has damaged companies around the Great Lakes. One of the reasons they're so invasive in the Lakes is that sea lampreys don't generally drain their food dry in their home environment (the Atlantic Ocean). They eat the fish but stop before it dies. The hosts of the sea lamprey in the Lakes are not evolutionarily suited to withstand the parasite's onslaught. They die as a direct result of the assault or later as a result of an infection caused by the wound left by the sea lamprey. Those who do survive have long-term health difficulties. The sea lamprey is not the only non-native species in the Great Lakes: