Our group of six researchers back rolled off the vessel near Jupiter, Florida, and began our descent to the sandy bottom nearly 80 feet (24 meters) below. As the wreck became visible, our team streamlined into formation to begin our task: searching for goliath groupers.
Closer to the wreck we saw more than 20 mature Atlantic goliath groupers, several of which were more than 3-6 feet (1-2 m) long and easily surpassed 200 pounds (90 kilograms). Exchanging hand signals, we quickly prepared and positioned the gear, lining up a tagging device to target one of the largest groupers near the bow of the wreck. With the release of the trigger, a fist-sized, brightly colored tag attached near the fish’s dorsal fin.
Satisfied with the attachment, the researcher recorded the tag number on a dive slate and then quickly reloaded and continued to the next fish. A diver followed behind with a device that held two underwater lasers at a known distance and in parallel with a small camera in the middle. Called twin laser photogrammetry, this device provides accurate length measurements simply by shining the two laser dots onto the side of the fish.
We continued to tag and measure as many goliaths as we could before our bottom time ran out. Back on the boat, we verified the number of fish tagged and measured on that first day. We would be doing a lot more work during this narrow and critical window of time to study their population numbers.
Goliath Grouper Protections
The Atlantic goliath grouper (Epinephelus itajara) is part of the family Epinephelidae, commonly known as groupers, which includes 159 species under 15 genera. Characterized by large mouths and heavy bodies, they have a long evolutionary history dating back more than 30 million years.
With a purported maximum size of 8 feet (2.4 m) and 800 pounds (363 kg), groupers live in depths from 3 to 160 feet (1 to 49 m), and their diet primarily includes crabs and fish, although it varies and can include octopuses, stingrays, turtles, parrotfish, and other bottom-dwelling species. They have a distribution in the western Atlantic from Florida to Brazil and in the East Pacific from Mexico to Peru.
Some fish have many fascinating adaptations that allow them to persist in times of change and scarcity in food and mates. Many groupers are protogynous hermaphrodites, which means they first function as females and later transform into males. This evolutionary transition evolved to ensure the successful reproduction and continuation of these species.
Goliath groupers form large aggregations during the late summer and early autumn to reproduce in a mass spawning event. Males and females gather in the same areas each year under the new moons to release
eggs and sperm into the water to create the next generation. Their biology is what makes them so vulnerable. Grouper spawning draws the largest adults together in one place, which historically has attracted fishers to target the abundance, leading to pronounced regional declines.
By the 1980s intense fishing pressure brought the Atlantic goliath grouper population close to local extinction in the United States, but federal and state laws intervened in 1990 to protect them. Their population increased during the first 20 years of the fishing closure but subsequently declined the next 10 years. The goal has been to continue monitoring their populations to document if recovery is indeed occurring or what may be hindering it.
The Florida Fish and Wildlife Conservation Commission (FWC) recently evaluated opening a limited number of juvenile goliath groupers to fisher harvest. Biologists, fishers, community leaders, nongovernmental organizations, politicians, divers, dive shop owners and stakeholders came together in the public process. The best available science suggested that the recovery was still ongoing and that opening even a small amount of harvest could have detrimental effects on the recovery.
Against scientific recommendation, however, the FWC in 2022 approved issuing up to 200 harvest permit tags for juvenile goliath groupers by a lottery system starting in the spring of 2023. The impact of this harvesting is not yet known and will be evaluated as part of long-term data collection from goliath aggregation sites off Florida’s coast.
Since the 1990s the fishing closure and protections have led to a blossoming dive ecotourism industry catering to people seeking opportunities to dive with and photograph these enormous fish. This ecotourism growth benefits dive shop owners, hotels, and restaurants and has changed the value of goliath groupers from simply a fishery resource to a shared community resource with a commercial value vastly greater than that gained only through fishing. Only time will tell which pressures and decisions will dictate the future of goliath groupers in Florida waters.
Population Studies
Our research team was back at the same site the next day with a new goal: Each diver would attempt to accurately count as many goliath groupers as possible and identify how many had the brightly colored tags attached from the previous day. With dive slates and pencils in hand, we covered as much area around the wreck as air allowed. Confirmation of tags was key, which is why dorsal positioning of the brightly colored tags was essential.
The process of tagging and resighting occurs at multiple sites in the goliath aggregation area and takes many days of diving. Under the leadership of Chris Koenig, PhD, the team has been collecting data for decades, estimating the population size based on how many fish are tagged in the area and how many are resighted. This data set will allow assessment of whether the population has increased or decreased over time. This “mark and resight” method is a valuable tool that helps quantify the status of recovery.
Goliath groupers are gentle giants. When you dive with them you may hear a loud boom sound, which is a form of territorial defense. They use their swim bladder to produce this sound when they feel threatened or startled or as a courtship display. When they boom you can feel it through your body and in your bones. It can trigger a series of booms from other nearby fish, which can sound like cannons going off around you. Sound travels faster underwater than in air, and this is a cacophony of fish sound.
On the last dive of the seasonal survey, I lingered for as long as I could with one single goliath. I was hanging on a pillar in the heavy current, and the fish just stayed there, flicking its tail as needed to maintain position — a move it does throughout its lifetime. I gazed into the fish’s eyes and wondered, How long will he survive? Will he be OK? Will I see him next year? He looked back at me, probably wondering what this wetsuited, four-limbed, air-bubble-blowing creature was.
My dive buddy tapped me on the shoulder. Air was low, and it was time to go. A single tear welled in my eye as I took one last look into his eyes and said goodbye. “Bye for now,” I whispered. I will be back to see you again, my gentle giant fish.
Explore More
Learn more about goliath groupers in these videos.
© Alert Diver – Q2 2025