Oceans around the world are getting warmer. This has resulted in approximately 130 new species appearing in the Mediterranean Sea. A wave of common lionfish is the latest species to appear there. These fish are striking to look at, but they also have a nasty habit of invading ecosystems where they do not have predators. The species is a close relative to the red lionfish, which has threatened the coastal ecosystems near the United States. The common lionfish was a rare sighting in the early 1990s, but recently many more sightings have been recorded. People have also seen pairs of lionfish, which leads them to believe the fish are now reproducing in the Mediterranean. It will be important to keep an eye on the common lionfish invasion to make sure that it does not get out of control.