A young Broad-barred Coral Goby, Gobiodon histrio, living alone, though with a crab, in a staghorn coral at Lizard Island in January 2020. Photo credit: Catheline Froehlich

Corals and goby fishes are slowly recovering, less than 3 years after the devastating climatic events that occurred at Lizard Island. While this is great news for Lizard Island, more recovery time is needed. The last 5 years have been rough for the reef, with two consecutive cyclones and two back-to-back mass bleaching events taking place. These disturbances have transformed what used to be a seascape full of staghorn and branching corals into one with fewer than 30% staghorn corals remaining, and vast stretches of bare substrate left spanning the seascape.

Prior to these catastrophic events, some of the staghorn corals, specifically the Acropora species, hosted small goby fish, usually the Gobiodon species. These fish lived in and amongst the staghorn coral branches receiving shelter and a home from the coral. The goby fish in return removed harmful algae, warded off fish that would otherwise try to eat the coral, and helped bring nutrients and water flow into the coral. Sadly, after the bleaching, few gobies were found still existing in the corals. Recently however, several different corals have been observed with resident gobies again.

These small adorable fishes are the focus of my PhD fellowship. Coral gobies play an important role in the maintenance of staghorn corals and have fascinatingly complex societies. In 2019, I was awarded the first Zoltan Florian Marine Biology Fellowship by the Lizard Island Reef Research Foundation. I will be studying the social circumstances surrounding the coral gobies in light of the recent climatic events. Over the next three years, I will be teasing apart whether living in societies is advantageous when faced with harsh and damaging climatic conditions.

FiveLine Coral Goby, Gobiodon quinquestrigatus, resting in between branches of a staghorn coral at Lizard Island in January 2020. Photo credit: Jemma Smith

Goby societies are comprised of multiple gobies (up to 15) harmoniously living within a single coral. Just like in humans, there is a hierarchy that keeps the peace for gobies, but interestingly it is based on the size of fish. The two largest fish mate together, and the others wait in line to take over once the mating pair disappears. Individuals in lower ranks need to keep their own growth in check, as getting too big could mean imminent eviction and death. The reward for doing so is granted once the lower ranking fish reach the end of the queue and finally become the larger mating fish. Although several goby species live in social hierarchies, other goby species actually live only in pairs.

Currently, we do not yet understand why some goby species live in groups while others live in pairs. Under the supervision of Marian Wong, Selma Klanten, and Mark Dowton and the University of Wollongong, I will be testing a theory that suggests species that live in groups will be more resilient to environmental disturbances than those living in pairs.

I am currently at Lizard Island on my first field trip under the fellowship and only 3 weeks in. I have already witnessed four times more corals and a third more gobies in my surveys this year than when I was here in 2018 (9 months after the last bleaching event). For the remainder of my three-year fellowship, I plan on monitoring existing populations of gobies to understand whether living in societies is an advantage for quicker recovery.

Catheline Froehlich is teaching volunteer, Jemma Smith, how to correctly measure staghorn Acropora coral along a transect. Photo credit: Selma Klanten

Catheline Y.M. Froehlich
Ph.D. Fellow: Zoltan Florian Marine Biology Fellowship
University of Wollongong