Lionfish attack prey with a style much like the science fiction character of the Terminator. Unlike most other animals, these fish will hunt down their prey until populations are completely wiped out.
Red lionfish, an invasive species in the Caribbean Sea and Atlantic Ocean, have been destroying native populations of fish in those waterways. Most species of fish predominantly hunt prey while populations are high. This makes finding a target easy, reducing travel time between potential sources of food.
As populations of prey animals decreases, predators usually move on to areas with easier hunting. Biologists call this density-dependent predation. The red lionfish, however, continues to hunt populations down until they become locally extinct.
"Lionfish seem to be the ultimate invader. Almost every new thing we learn about them is some characteristic that makes them a more formidable predator. And it's now clear they will hunt successfully even when only a few fish are present. This behavior is unusual and alarming," Kurt Ingeman, a PhD candidate from Oregon State University, said.
Natural reefs were replicated in the Bahamas, and the regions were stocked with fairy basslet - common aquarium fish that are a favorite food source for red lionfish. Researchers studied the rates at which the prey was consumed by the predators. This data was then compared to rates of predation on basslet from native species, like trumpet fish and groupers. Red lionfish were found to hunt four times as many prey fish as native varieties. Population levels of the fish were also altered by researchers in an effort to understand hunting behaviors.
Red lionfish are often called a ghost fish for their ability to hide in coral reefs, with white and tawny stripes running down their sides. They grow up to 15 inches in length, and can deliver a toxin to the target of their wrath.
Ghost fish also possess some unique characteristics that allow them to become more than formidable hunters. They are able to live far underwater, in a wide range of conditions, and eat a range of other fish species. They reproduce rapidly, almost year-round, and their status as an invasive species in affected areas means they may not be recognized as a predator by the species on which they feast.
Over 90 percent of native fish have been wiped out by lionfish in some of the most-affected regions. The invasive species first reached the Atlantic Ocean in the 1980's, and they now cover a territory equal in size to the United States.
Fish that are the targets of ghost fish may, one day, adapt to the presence of the Terminator-like hunter.
"We know that fish can learn and change their behavior, sometimes over just a few generations. But we don't have any studies yet to demonstrate this is taking place with native fish populations in the Atlantic," Ingeman told the press.
