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Tracking a Group of Groupers

Guest post by Kristine Stumppostdoctoral research associate, Shedd Aquarium

The beautiful and iconic Nassau Grouper was once one of the most important fishery species in the wider Caribbean, but due to heavy over exploitation is now scarce in many coral reef ecosystems throughout its native region. As mesopredators, groupers play a vital role in maintaining ecosystem balance through interspecific competition and predation. They are important not only ecologically, but also economically and culturally, particularly in The Bahamas. Bahamians have fished for grouper for centuries, and the fishery supports thousands of livelihoods, saturating the social fabric of the country. However, groupers are particularly susceptible to fishing pressure because they form annual spawning aggregations at sites that are often well-known by fishermen.

In the face of rapid grouper population declines and the subsequent disappearance of once reliable aggregations, the Shedd Aquarium’s Daniel P. Haerther Center for Conservation and Research has embarked on a multi-year research project, in partnership with the Bahamas Department of Marine Resources (DMR), Bahamas National Trust (BNT), Perry Institute for Marine Science and University of Exeter to enhance conservation and management efforts of the endangered Nassau Grouper in The Bahamas. Our overall project goal is to help DMR better manage the fishery of this iconic species in a more sustainable way through science-based adaptive management.

2014 was a busy year for our endangered Nassau Grouper project in The Bahamas. To understand the groupers’ movements to various annual spawning aggregations, we put in motion a large-scale telemetry project across several Bahamian islands as a two-part process: 1) surgically implanting grouper with acoustic tags, and 2) deploying monitors along the seafloor to pick up the signals from our tagged grouper. Aboard Shedd’s research vessel, the R/V Coral Reef II, we tagged a total of 46 fish in two different spawning sites, deployed 18 bottom monitors that will record the tagged groupers’ movements and conducted dozens of diver surveys for spawning stock assessments at several aggregations.

Kristine Stump (bottom center) and research divers deploy a bottom monitor in The Bahamas.
Kristine Stump (bottom center) and research divers deploy a bottom monitor in The Bahamas.

The Bad News

Unfortunately, not all is right in the grouper world. Through our site visits during the spawning time, we witnessed severely reduced numbers of grouper at some aggregations, and some locations that were once thriving were even defunct. In addition, this past December and January we witnessed illegal fishing at the aggregation sites, which are completely closed to fishing during the winter spawning period. In fact, about 30% of the Nassau Grouper we counted were inside fishermen’s traps.

The Good News

Luckily, not all the news is bad. At one aggregation site that has been monitored for several years, Nassau Grouper abundance was slightly higher than in recent years, potentially indicating an uptick in the number of fish that use that site, or at least a break in the downward trend. In addition, several of our partners were able to simultaneously visit another more remote aggregation, and found a fairly healthy abundance of Nassau Grouper.

Up Next

2015 promises to be an exciting year for Shedd’s endangered Nassau Grouper project, as we continue with novel telemetry methods. In addition, through our partners and collaborators, we have expanded the scope of our research to include genetic connectivity, reproductive endocrinology, stress physiology, bathymetric mapping and biophysical modeling.  We’ll be returning to The Bahamas at the end of March to download a set of bottom monitors to see what information they have been collecting about our tagged grouper over the past year. Stay tuned for more updates!

Research divers and crew of Shedd’s research vessel, the R/V Coral Reef II after a successful grouper tagging cruise.
Research divers and crew of Shedd’s research vessel, the R/V Coral Reef II after a successful grouper tagging cruise.

Dr. Kristine Stump joined Shedd in 2014 as a postdoctoral research associate in the Daniel P. Haerther Center for Conservation and Research. Her work focuses on spawning aggregations of Nassau grouper. Her findings will assist the Bahamas Department of Marine Resources to establish a science-based management plan for the endangered species.