The sea lamprey have a complex life cycle. They spend the first four to five years of their life in streams, living in the substrate of streams as they slowly grow. Then they reach a stage called transformers, which is that they transform and become a parasitic form, and that's when they move out to the lakes. At this point they're still fairly small, but then they attach onto the side of a fish—the third slide had a picture of the sea lamprey and a hole in the side of the fish—and basically drill through the side of the fish and start to consume the fish from the outside, sucking out the juices. It can kill the fish, depending on the size of it, but for the commercial fishery it causes damage to the fish. Even if the lamprey drops off after it's been attached for some time, it can leave damage. Therefore, if that fish is caught by the commercial fishermen, people don't want to fillet a fish with a hole in the side of it from a sea lamprey.
On April 2nd, 2012. See this statement in context.