Underwater ‘Doorbell’ Camera Helps Researchers Catch Coral-Eating Fish

Florida marine scientists have been working to help reverse a long-term decline in coral reefs by using doorbell-style surveillance cameras to catch fish in the act of eating coral laid as bait.

They found that three species — stoplight parrotfish, redband parrotfish and foureye butterflyfish — were responsible for eating over 97 percent of the corals.

“Intense fish predation on newly outplanted corals has emerged as a major restoration bottleneck. The main goal was to address our lack of knowledge of the fish species that target corals after outplanting,” said project leader Diego Lirman, an associate professor at University of Miami (UM)’s Rosenstiel School of Marine, Atmospheric, and Earth Science, as The Guardian reported.

The footage captured by the specialized cameras at an offshore reef close to Miami can be used to inform coral repopulation efforts. Coral cover in Florida has declined by 90 percent since the 1970s, with especially dire bleaching events due to human-caused global heating decimating corals over the past two summers.

“Identifying the fish species responsible for coral predation would allow practitioners to avoid reef sites or areas within sites with high abundances of those species and, similarly, select the right coral species for the right outplanting site,” Lirman said. “The coral-baited underwater cameras provide insight into corallivore behavior and preferences and allow documentation of predation at various sites rapidly and without incurring the cost of outplanting.”

The research team, funded by the Fish & Wildlife Foundation of Florida, designed and built the recording devices using waterproof-encased GoPro cameras that they attached to a frame made from PVC piping and lead weights for stability.

Once the retrofitted cameras were fine-tuned, divers secured them to the Paradise Reef seabed near Key Biscayne using cable ties and masonry nails.

They set the coral-baited remote underwater video station (C-BRUVS) so that it would record time-lapse video, the footage of which was collected first after periods of 24 and 48 hours, then weekly for six weeks.

Data collected during the study showed that redband parrotfish were the biggest coral bandits, responsible for 56.3 percent of bites on the fragments of nine coral species.

Foureye butterflyfish were the second-most voracious eaters of the corals with 36.9 percent, followed by stoplight parrotfish with just four percent.

Lirman said the three species “showed clear preferences” for two or three specific coral types, which received over 65 percent of all recorded bites.

“By identifying, for the first time, the main fish predators as well as their preferred diet, reef restoration practitioners can select sites and species that would minimize predation impacts and maximize restoration success before large-scale, costly outplanting is implemented,” Lirman said.

Lirman said similar research in the future could use elements of artificial intelligence (AI).

“Analyses of the videos were extremely time-consuming, requiring a constant rewinding and stopping of the footage to record and annotate coral/fish interactions,” Lirman explained. “It will be beneficial to explore AI software that can be trained to identify fish and their behaviors to automate the analysis process.”

UM marine scientist Erin Weisman presented the findings to a symposium of conservation leaders with Reef Florida last November at the Phillip and Patricia Frost Museum of Science in Miami.

“Florida’s Coral Reef is facing one of its greatest challenges yet, and our team is committed to pioneering new approaches to ensure its survival,” said Andrew Baker, a marine biology and ecology professor and director of the Rosenstiel School’s Coral Reef Futures Lab, in a press release from UM.