Parasite-mediated enemy release and low biotic resistance may facilitate invasion of Atlantic coral reefs by Pacific red lionfish (<Emphasis Type="Italic">Pterois volitans</Emphasis>)

Successful invasions are largely explained by some combination of enemy release, where the invader escapes its natural enemies from its native range, and low biotic resistance, where native species in the introduced range fail to control the invader. We examined the extent to which parasites may mediate both release and resistance in the introduction of Pacific red lionfish (Pterois volitans) to Atlantic coral reefs. We found that fewer lionfish were parasitized at two regions in their introduced Atlantic range (The Bahamas and the Cayman Islands) than at two regions in their native Pacific range (the Northern Marianas Islands and the Philippines). This pattern was largely driven by relatively high infection rates of lionfish by didymozoan fluke worms and parasitic copepods (which may be host-specific to Pterois lionfishes) in the Marianas and the Philippines, respectively. When compared with sympatric, native fishes in the Atlantic, invasive lionfish were at least 18 times less likely to host a parasite in The Bahamas and at least 40 times less likely to host a parasite in the Cayman Islands. We found no indication that lionfish introduced Pacific parasites into the Atlantic. In conjunction with demographic signs of enemy release such as increased density, fish size, and growth of invasive lionfish, it is possible that escape from parasites may have contributed to the success of lionfish. This is especially true if future studies reveal that such a loss of parasites has led to more energy available for lionfish growth, reproduction, and/or immunity.