The mating ritual of the Nassau grouper is an attention-grabber. Every year, prompted by a winter full moon, these normally solitary fish amass in the same spot. After a few days, their color pattern darkens to signal readiness and they launch a series of sprints toward the ocean surface, visibly clouding the water with sperm and eggs.

Unfortunately, these spectacular spawning aggregations also leave the Nassau grouper highly vulnerable to overfishing. For example, when an aggregation appeared off Little Cayman in 2001, it took a few fishermen a matter of days, spread across two fishing seasons, to catch approximately 5,000 of the estimated 7,000 fish that had gathered there—a rate of removal the population cannot withstand.

Yet today, thanks to a government-science partnership, the site has become one of the few healthy aggregations of Nassau grouper in the world, and the species is rebounding elsewhere in the Cayman Islands.


Nassau grouper began declining in the 1950s throughout the Caribbean, South Florida, Bermuda and the Bahamas. By the 1980s, fishermen in the Cayman Islands asked scientists at their territory’s Department of Environment (DoE) to investigate. The agency conducted groundbreaking research on the demography of the species and collected several years of data that showed a steady decline in catch. It recommended closing the fishery in alternate years, but this was not done, and the fishery collapsed by the early 1990s.

A decade later, a few local fishermen found a previously unknown Nassau grouper aggregation in Little Cayman teeming with fish, and quickly capitalized. Many said the aggregation included groupers from offshore banks and other countries in the Caribbean region and argued that a heavy catch would therefore have minimal impact on the local stock.

Our group of policy makers, scientists and academics was not so sure. To better understand the population, in 2001 some of us—at the Cayman DoE and the nonprofit organization Reef Environmental Education Foundation (REEF)—began a research partnership called the Grouper Moon Project, which we see as a model for natural resource science.


One reason for the partnership was that DoE, despite the expertise of its scientists, did not have the resources for an intensive investigation of a single species. So the agency brought in academic scientists from the Scripps Institution of Oceanography at the University of California, San Diego, and from Oregon State University. Additional funding, including from the Lenfest Ocean Program, helped the partnership continue for more than a decade.

The collaboration focused its research on the needs of those who would use it—DoE and the fishermen and other citizens the agency represents. This put DoE in the lead in setting the overarching research question: What measures are most likely to lead to recovery of Nassau grouper and the restoration of a sustainable fishery? The academic scientists decided how to answer that question, but they frequently turned to the government scientists to confirm that the methods would fit the agency’s needs.

In other words, we listened to each other, and we weren’t afraid to change our minds based on what we learned. The best example of a positive change was our decision to expand the research beyond Little Cayman.

Had the academics been calling the shots, they might have been content to stay on that island, because a larger aggregation is more likely to yield interesting results. But DoE scientists pushed to expand to the nation’s two more populated islands, Grand Cayman and Cayman Brac, where research is more difficult because groupers are fewer and the aggregations deeper and harder to observe, but also where recovery would restore a fishery that far more citizens could access.


After several years of tagging and tracking adult groupers, snorkeling in search of juveniles and measuring fish with lasers, the project produced several important results that became the evidence base for a sweeping Caymanian conservation law that passed in 2016. Fishermen largely supported the law as necessary to sustain the population.

Here are some of our main findings, and the policies that were enacted in response:

  • All of Little Cayman’s spawning Nassau grouper are local to that island (the same is true for all the islands), meaning that local conservation efforts would produce local benefits. Furthermore, all resident Nassau grouper visit their local aggregation every year. In response, in 2003 the government banned grouper fishing at aggregation sites during spawning season for eight years.
  • Age at maturity was established, as were reproductive rates. In 2016, parliament used this information to set a minimum size limit to allow fish to grow to maturity, and a maximum size limit to retain old fish, which produce more and larger eggs. It also banned fishing for Nassau grouper everywhere in Cayman waters during the spawning season, not just at aggregation sites.
  • Successful reproduction is sparse in most years, with aggregations yielding only occasional bumper crops of juveniles. The 2003 fishing ban had an eight-year sunset period, but in recognition that this span of time would not guarantee a good year for young fish, the Cayman Islands Government did not put an expiration date on its 2016 conservation measures.

The grouper recovery on Little Cayman continues to be remarkable. The population has grown from as few as 1,000 fish in 2003 to as many as 8,000 in 2018, plentiful enough that they can now be caught from shore in the open season. And in the waters around Cayman Brac, it has grown from as few as 300 groupers to as many as 1,000. No recovery has been detected on Grand Cayman, but we hold out hope for some banner years to restart that population.

It’s true that this effort benefitted from circumstance: The Cayman Islands is a small territory, which can make it easier for scientists to join the policy dialogue. Further, the grouper crash in the 1990s gave us a level of freedom to experiment that comes only when you have nothing left to lose.

But we’re not special. Scientists and policy makers around the world can replicate our success—if they listen to each other.