Almost two years ago I wrote a blog post on a rapid marine invasion that is currently occurring in the western Atlantic. In the mid-1980s lionfish of the species Pterois volitans were released in Florida. The fish were likely dumped into the ocean by some aquarium fish owners that for some reason didn't want to keep their fish anymore. The native range of this species is around Indonesia but they are now established on coral reefs across the western Atlantic Ocean, Caribbean Sea and Gulf of Mexico, and the invasion continues to spread while reef biodiversity and biomass rapidly declines. The high rate of fish mortality also poses an additional threat to coral reefs themselves, which can become covered with algae if enough fish are not present to eat the algae and keep it under control.
At the time of my post two studies utilized DNA Barcoding of lionfish stomach content to identify prey species for a better estimate on the breadth of the diet of these invaders. It turned out that the lionfish, as it is often with invasives, are generalists. Prey fish were members of groups that fit within the gape size range of lionfish. I was part of one study and we concluded that only well-resolved diet information combined with prey availability data can help to identify the species most at risk from lionfish predation.
Consequently, some of my coauthors now started to identify general traits of prey that predict vulnerability to predation, and examine diet selection at different spatial scales. This new study confirmed that lionfish have a voracious appetite and will eat almost any fish smaller than they are, but it also shows that they do have their favorites.
They find it easier to stalk and attack solitary fish, rather than those in schools. They like to hunt at dusk, near the bottom, and for some reason tend to avoid fish that clean off parasites from other fish species that are common in a marine environment. Together, vulnerable traits heighten the risk of predation by a factor of nearly 200.
Having all the traits that make them vulnerable, for instance, raises a serious question about the ability of some species to survive the lionfish invasion, such as the Exuma Goby (Elacatinus atronasus), a small fish native to one area of the Bahamas. It not has its own Facebook page but more importantly many traits lionfish prefer and maybe therefore threatened by the invader.
Some of these findings may even be relevant to other invasive species problems, such as expansion of the Burmese python in the Florida Everglades and the spread of Asian tiger prawn into the Gulf of Mexico.
Finally, our study shows that a functional, or trait-based, approach has value for generating predictions about the effects of prey selection on the structure of ecological communities. Current thinking about predator–prey interactions can be broadly characterized into two prevailing paradigms: a species-based view, in which food webs are constructed by quantifying the interaction strength between pairs of predators and prey , and a size-based view, which classifies predator–prey interactions based on body size, largely ignoring species identity. Our study is the first to identify general traits of prey that predict vulnerability to predation and indicates that a trait-based view of predator–prey interactions, in which variation in morphology and behaviour determines prey selection, also has significant influence on species interactions within ecological communities. It is also, to our knowledge, the first to examine diet selection simultaneously at two spatial scales. Importantly, both our in situ observations of predation and broadscale analyses of stomach contents identified the same prey traits as important drivers of diet selection.