Red Grouper remove sediment, bits of broken shells, shed molts from crabs and lobsters, dead algae, and other detritus from holes on the seafloor. In the process, they increase the amount of benthic habitat available to other organisms. For my PhD dissertation, I studied the effects of Red Grouper on the biodiversity of Florida Bay hardbottom habitats.

In general, solution holes – crevices in the limestone bottom that are cleaned out by the Red Grouper – hosted more species of fishes and invertebrates when Red Grouper were present compared to solution holes without Red Grouper.

To investigate the processes driving these patterns – Why were the faunal communities more diverse around active “grouper holes”? Was it simply because the grouper created habitat? Or are there more complex interactions occurring between the colonizing species and the grouper? – I used a combination of direct observations – counting fish while SCUBA diving – and experiments where I manipulated the presence of grouper to determine the mechanisms that controlled diversity.

The ultimate goal of this research is to explore a unique example of a marine ecosystem engineer to gain a more complete understanding of the mechanisms by which biodiversity is maintained in marine ecosystems and to better comprehend the full ecological effects of fishing. In this case, a popular fisheries species – Red Grouper – also plays an important ecological role in the ecosystem. Digging holes creates habitat for other species, including some that are themselves important fisheries species like lobsters and snappers. When Red Grouper are caught, what happens to the habitat? How might fishing for Red Grouper affect lobster or snapper populations?

By studying the communities that develop around Red Grouper habitats, I was able to quantify the strength of interactions between the grouper and the other species that inhabit solution holes. Understanding these interactions between organisms that are targeted by fisheries will ultimately help refine sustainable fishery practices and allow us to maintain biodiversity in the oceans.

Citations of recently published papers describing this research:

Ellis RD, FC Coleman, and CC Koenig. 2017. Effects of habitat manipulation by red grouper, Epinephelus morio, on faunal communities associated with excavations in Florida Bay. Bulletin of Marine Science. 93: 961-983. https://doi.org/10.5343/bms.2017.1002

Ellis, RD and ME Faletti. 2016. Native grouper ameliorates negative effects of invasive lionfish: Evidence of a behaviorally-mediated indirect interaction. Marine Ecology Progress Series. 558: 267-279. https://doi.org/10.3354/meps11808