Invasive red lionfish (Pterois volitans) affect persistence of the bridled goby (Coryphopterus glaucofraenum)

Background/Question/Methods

Invasive lionfish are highly effective predators that severely threaten Caribbean and Atlantic fish populations.   Most coral reef fish populations are regulated by density dependent mortality due to predation.  Because lionfish can consume significantly more small fish than ecologically similar native predators, they have the potential to disrupt this regulatory process.  The bridled goby is a model native species that lionfish readily consume.  Because bridled goby populations are regulated by density dependent mortality due to predation and available refuge space, lionfish may alter and, potentially, destabilize the regulatory process that maintains bridled goby populations.  Therefore, I compared the per capita mortality of adult bridled gobies (2.5cm – 4.5 cm) on 3.5m² nearshore patch reefs among four treatments:  (1) one native resident predator (grasby grouper, Cephalopholis cruentatus), (2) one lionfish, (3) one resident predator and one lionfish, and (4) no predator control.  Bridled goby abundances ranged from 4 to 36 fish per reef, within naturally occurring densities, and all predators ranged in size from 7 to 10 cm.

Results/Conclusions

I found that mortality was density independent across all treatments.  Reefs with a lionfish, treatments (2) and (3), showed a significant additive effect on the per capita mortality of bridled gobies when compared to control reefs and native predator only reefs.  Remarkably, per capita mortality increased to near 100% on reefs with a lionfish, both treatments (2) and (3).   It is clear that lionfish have a devastating effect on bridled goby populations and can remove all gobies from small patch reefs.  Thus, lionfish have to potential to cause local extinction of bridled gobies.