Exploring Grouper and Snapper Populations in The Bahamas

Latest update July 27, 2019 Started on January 1, 2014

Shedd Aquarium’s research team is working to ensure the future sustainability of grouper and snapper populations in The Bahamas. We’re tracking their movements to see how many individuals are present and where they travel for spawning.

January 1, 2014
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Following the great success of the test drive with the teens I tried some solo-piloting in Haigh Quarry, a man made body of water southwest of Chicago following a dive.

We launched the Trident from a floating dock. Immediately fish were attracted to the lights of the Trident, and a school of sunfish played with the Trident during our test run. The visibility was better than Lake Michigan had been on Thursday.

While the surface water was a balmy 84 degrees F, the water dropped to the mid 50s at roughly 25 feet. Watching the temperature read-out from the Trident was a fun bonus on this trial run. We plan to continue to practice piloting the Trident in preparation for the August research trip to study grouper.

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This spring, we received our grant-funded Sofar Trident ROV through National Geographic’s Science Exploration Education initiative, allowing us to explore underwater environments from land or boat. As Shedd Aquarium is based in Chicago, we took the ROV out for our first test drive in Lake Michigan today.

Having purchased the optional controller that goes with the Trident, I was told it would be similar to playing a video game. Only thing is, I was never that good at video games – and they were much simpler in my childhood (Mario Go Kart on SuperNES, anyone?). Luckily for me, Shedd has some experts at video games in the building – interns and students from the aquarium’s Teen Learning Lab)

After giving the teens an introductory talk on the life history and biology of Nassau grouper along with their population status throughout their range, we spoke about why the Trident is so useful. To sum it up, Nassau Grouper can be found deep (up to 200 meters!). Placing a dive team in the water takes time and has a safety risk associated with it. The Trident will enable us to survey areas that are either unsafe for divers to enter or before we decide to put divers into the water, saving us valuable time.

Now that everyone was on the same page, we headed to Lake Michigan. Thunderstorms rolled through the area earlier in the day, so the water visibility was not optimal. To better see the controller screen in the intense sun we used an umbrella, which went over quite well. The teens quickly oriented to the controller and were zooming around the lake. We captured some fish and great footage of the benthos.

While I’m not yet as skilled as some of the teens with the controller, we now know how to dive and maneuver the Trident, which is just in time for our research trip in August to the Berry Islands, The Bahamas to survey for Nassau grouper.

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In The Field

A recent United Nations report warned that as many as 1 million species are now at risk of extinction if we don’t act – a biodiversity crisis that touches vital ecosystems all over the globe. While grim news, this report shines a light on the need to understand how we can protect our planet’s wildlife. For Shedd Aquarium, we do so through scientific research and public education.

Teaching and inspiring the next generation of conservation scientists comes in many forms at Shedd. As a research biologist myself, I use my background studying grouper to engage Chicago-area college students in conservation research.

Each spring, Shedd Aquarium partners with the Associated Colleges of the Chicago Area (ACCA) to teach a college-level course called Marine and Island Ecology of The Bahamas that offers upper-level, undergraduate students the opportunity to connect with Shedd’s animals, experts and field research programs. The course is spread out over five Saturdays at the aquarium, followed by an immersive research excursion aboard Shedd’s research vessel, the R/V Coral Reef II.

This year, 18 students from 11 different ACCA colleges joined us in The Bahamas over the course of about 2 weeks. Everyone boarded the research vessel in Nassau and then sailed south to the Exumas, where we conducted the field component of the course both inside and outside the Exuma Cays Land and Sea Park, the first land and sea park in the world, created in 1958 and covering 176 square miles.

In addition to learning about how to identify species in the wild, individual ecosystems and conservation management, the students completed mini research projects working with scientists from the Marine Research team at Shedd Aquarium, like myself. The projects included: a study on coral tolerance to warmer waters; assessing shark and grouper populations with underwater video footage; conducting a survey of juvenile conch in a conch nursery; and comparing the level of predation experienced in seagrass and coral habitats .

Even after long days of snorkeling and evening lectures, the students worked in groups to create blogs that share their experience. The upcoming posts will be the research through their eyes!

Interested in becoming a student on a future ACCA trip? Find out more here.

Shedd Aquarium also teaches an upper-level Freshwater Ecology course each fall, find out more here.

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Our marine research team had a very successful field expedition aboard Shedd’s R/V Coral Reef II in The Bahamas at the end of March. The team split into four research groups focusing on corals, lobster, parrotfish and sharks. The groups focusing on sharks and lobster were also able to tie in some of our Nassau grouper research as they worked.

Dr. Andy Kough, research biologist at Shedd Aquarium, led the lobster team. He was focusing on collecting information on how many spiny lobster were present throughout select locations and how big each was. To do so, he used a special underwater tool called laser-video calipers, which were on loan to Shedd Aquarium from Dr. Brice X. Semmens, associate professor in the Marine Biology Research Division at Scripps Institution of Oceanography, and the Reef Environmental Education Foundation (REEF).

The laser-video calipers consist of two parallel lasers with a camera mounted in-between them. With the camera filming, a diver works to get the lasers pointed on an object of interest, like the hard upper shell of a spiny lobster called a carapace. The video can later be turned into still images, and since the laser dots are a known distance apart, we can measure the object the lasers are on.

This method can also be used to collect the length of fish, although it is a little trickier since fish move quickly and the laser dots can spook them! To use the laser-video calipers on fish like Nassau grouper, the fish needs to be parallel to the camera (perpendicular to the lasers) to ensure we capture the total length of the fish, or the measurement from the tip of the snout to the end of the tail, or caudal fin.

Dr. Kough and his colleagues were able to measure 71 Nassau grouper with these laser-video calipers. This included fish from inside the Exuma Cays Land and Sea Park and some outside to the north and south of the park.

Most fish were around 50 cm total length, which means they are most likely sexually mature fish, but they also find some fish as small as 20 cm! These smaller fish are probably between 1 and 2 years old, perhaps spawned over the winter from 2018 to 2019. Finding fish this small is really exciting, because it indicates the presence of an active spawning aggregation relatively nearby that had successful recruits into the Exuma Cays Land and Sea Park.

In total, the team spent 831 minutes diving outside the park and 580 minutes diving inside the park. That’s almost a full day underwater!

We’re looking forward to spending more time underwater and in the field this spring. During our next expedition back to The Bahamas this May, we’ll be bringing a group of Chicago-area college students to participate in our research! Stay tuned for more debriefing from the field team.


Researchers are all safely back at the John G. Shedd Aquarium, having returned from a ten day research trip aboard the R/V Coral Reef II. Stay tuned for a post on some the work they did related to Nassau Grouper later this week!


Wondering how we will be getting around The Bahamas on our upcoming trip? Shedd Aquarium has an 80-foot research vessel, the R/V Coral Reef II, that helps us access far-out islands in The Bahamas.

This custom-designed floating field station and laboratory was built with research in mind and has multiple habitats, or “live-wells,” that allow us to temporarily bring fish on-board the vessel to collect data on the animals and tag them before releasing. This includes one 1,800 gallon live-well and multiple smaller 100 gallon live-wells. The R/V Coral Reef II also stores and launches three smaller boats, or skiffs, that enable scientists to access shallower areas that the larger vessel could not go.

Our research team will board the R/V Coral Reef II in Miami tomorrow and then cross the Gulf Stream before reaching The Bahamas, where we will pick up additional scientists for the project. Our Shedd research team consists of Dr. Steve Kessel, Dr. Andy Kough and Dr. Ross Cunning, who will be joined by researchers from Perry Institute of Marine Sciences, Cape Eleuthera Institute, [University of Miami] (https://welcome.miami.edu/), Bahamas Reef Environmental Education Foundation (BREEF), and Bahamas National Trust.

For this upcoming trip, the research will be multifaceted, covering organisms from nearly every major level of the food chain. Specifically, research will focus on sharks, coral, conch and lobster, in addition to grouper and snapper. So, we have a whole lot of equipment to bring!

We will be bringing baited remote underwater videos (BRUV’s) for assessing grouper, snapper and shark populations; laser calipers for measuring fish and invertebrates; a drone for scouting locations of shallow-water coral reefs; a variety of tagging equipment for sharks and grouper; and much more.

Today, the scientists shipped the final set of gear from Chicago to Miami to load onto the boat. We're looking forward to good weather and another successful research expedition to The Bahamas. Once the team returns to Chicago we will post updates on some of their findings.

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This week, our research team at Shedd Aquarium is setting out for our first marine research expedition of 2019. On this trip, our research biologists will be studying sharks, corals, spiny lobster and grouper. While a few of these studies are relatively new, we’ve been collecting data on grouper for several years. On this trip, we will continue studying Nassau grouper’s spawning aggregations around The Bahamas.

There are an approximated 40 Nassau grouper spawning aggregations throughout the archipelago, however very few have been validated or scientifically studied. Since we began studying these important mesopredators in 2014, we have focused on describing Nassau grouper migrations along Andros Island, The Bahamas, which is bordered by one of the longest barrier reefs in the world. Using acoustic telemetry, a technology that uses sound pulses to track individual fish movements, we can understand where Nassau grouper travel throughout the year and during their aggregations.

After spending two years tagging Nassau grouper during their full moon aggregations, we documented the collapse of one of these 40 aggregations – a spawning aggregation at High Cay off the east coast of Andros in The Bahamas. Our findings were published in 2017 in the Bulletin of Marine Science in partnership with the University of Exeter, Perry Institute for Marine Science and the Bahamas National Trust.

This aggregation likely existed for decades and its collapse may be the result of fishing pressure and the overexploitation of the species due to their natural reproductive behaviors. It indicates that, despite existing protections, Nassau grouper populations were declining as of 2014 – 2015.

We have and will continue to study these animals and their movements to document more recent declines, if any. After we cruise from the U.S. to The Bahamas this week, I look forward to sharing more updates about this important research.

Expedition Background

The John G. Shedd Aquarium has a long history of marine research and conservation efforts in The Bahamas, a country we’ve highlighted in our exhibits since we opened in 1930. We have made a commitment to preserving the ecological integrity of aquatic ecosystems, sustaining populations for some of the world’s most important key indicator species and enhancing human livelihoods that coexist with, and rely on them.

One of our marine conservation research projects focuses on studying Nassau grouper in The Bahamas. Growing up to a substantial 4 feet and 50 pounds, the Nassau grouper is one of the most important food fishes throughout the Caribbean and West Indies. It is also one of the most rapidly disappearing.

Many groupers and snappers, including the Nassau grouper, form spawning aggregations to reproduce. Due to the highly predictable nature of these spawning aggregations, they have historically been easy targets for fishermen. Aggregation fishing has led to the collapse of many such spawning aggregations, where so many fish have been removed that the aggregations cease to form.

For Nassau grouper in most of the Caribbean, these spawning aggregations form following the full moon in the winter months. For The Bahamas, this happens following the full moon in December or January. Since 2014, researchers from Shedd have been studying the Nassau grouper spawning aggregations in The Bahamas by using acoustic telemetry. This research method involves surgically implanting the fish with acoustic tags that are about the size of a AA battery. As the fish swim through the ocean, these tags then register on transmitters fixed to the ocean floor throughout the Caribbean region. This technology allows us to track individual groupers’ movements across multiple years, including during these aggregations.

In 2019, we are continuing this work aboard Shedd Aquarium’s floating field research station, the R/V Coral Reef II, and will be expanding our research to include other species, including snapper and other species of grouper, all that are culturally and commercially important and species of conservation concern. Our goal is to work with our partners to create fisheries assessments that can be used to inform sustainable fisheries management plans.


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