Researchers compared invasive lionfish to "The Terminator."
The fish are invasive to the Pacific Ocean. Most predators move to new areas when their prey starts to get depleted, but lionfish tend to stay even after local fish numbers have dropped to clean off the rest, Oregon State University reported.
"Lionfish seem to be the ultimate invader," said Kurt Ingeman, a researcher from Oregon State University. "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."
The research was conducted on replicated natural reefs in the Bahamas. Predation rates were compared between reefs with invasive lionfish and those with only native predators. They measured concentrations of fairy basslet, which are common prey in the region. The team found when the prey is at a low population density the rate of mortality was four times higher than if only native predators were present.
"Reef fish usually hide in rocks and crevices for protection, and with high populations, there is a scramble for shelter," Ingeman said. "Native predators take advantage of this situation by mostly eating when and where prey are abundant. As prey population levels decline, it takes a lot more energy to catch fish, so the predators often move on to other areas."
Due to this process, dubbed "density-dependent" predation, the prey's population tends to shrink when it gets too large and grow when it gets too small. This keeps the populations relatively balanced. Invasive lion fish will instead wipe out the entire population; and prey often do not recognize them as predators. Lionfish are lethal hunters and have defensive poisonous spines; they can thrive at extremely deep ocean levels.
"There's a strong pressure here for natural selection to come into play eventually," Ingeman said. "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."
