Researchers tracking the critically endangered Nassau grouper have lauded conservation efforts to resuscitate the population in the Cayman Islands.

A new study from researchers at the Scripps Institution of Oceanography at the University of California San Diego, published this week, indicated that the annual aggregation of Nassau groupers in Little Cayman is now the largest remaining identified aggregation of the fish in the world. This is a major change from two decades ago, when the Little Cayman Nassau grouper population was considered to have collapsed.

The researchers attributed the successful recovery of the local Nassau grouper populations to an approach involving government agencies, academic researchers and non-profit organisations.

They said they were astonished at how quickly the population had recovered over the last decade.

“The aggregation on Little Cayman [increased] from around 1,200 fish in 2009 to more than 7,000 in 2018. This growth was due, at least in part, to a rapid increase in the addition of new, younger fish to the aggregation,” the researchers said in a media statement on their findings.

While the numbers are a positive testament to local efforts, the Department of Environment remained cautious.

“While the numbers are very encouraging and we don’t want to downplay that, it is still very important to have Nassau grouper fishing restrictions in place for the survival of the species. Remember, the closed fishing season runs from 1 December to 30 April. It will take a lot more patient conservation work to bring this species back from the brink. They remain critically endangered.”

What the researchers found
The study, titled ‘Recovery of critically endangered Nassau grouper (Epinephelus striatus) in the Cayman Islands following targeted conservation actions’, was published in the journal Proceedings of the National Academy of Sciences.

The researchers used a two-pronged approach that included tagging and video census data for monitoring and counting the Nassau grouper populations.

The report noted that, by 2001, the Nassau grouper population in the Cayman Islands appeared to have “completely collapsed”. Over the past 15 years, since the monitoring programme began, the numbers in Little Cayman had recovered significantly.

“Census data from Cayman Brac, while more sparse, show a similar pattern. These findings demonstrate that spatial and seasonal closures aimed at rebuilding aggregation-based fisheries can foster conservation success. Reef fishes that form fish-spawning aggregations (FSAs), including many species of grouper, are at high risk of being over-fished when fisheries target their FSAs,” the study said.

“This really demonstrates the power of this collaborative approach to conservation,” said the report’s co-author Christy Pattengill-Semmens, Reef Environmental Education Foundation director of science.

“We were able to monitor the population and provide information to support management as the data came in, allowing the Cayman government to respond rapidly with policy changes. These efforts have been successful because of the strength of the partnerships among the government, academic research groups, and non-profits,” she added.

Those policy changes included fishing restrictions.

“Because of the implementation of these deliberate, science-based conservation strategies, Little Cayman is now home to the largest remaining identified Nassau grouper aggregation anywhere in the world,” the study stated.

The researchers, in their study, said they were unable to collect the tagging and video census data necessary to include Grand Cayman in their analysis. However, the management actions taken by the Cayman government encompass all three islands.

“Although exceptionally coarse, observational evidence from 2012 and 2018 suggests that the FSA has remained highly depressed (500 or less fish) over the same time frame that Little Cayman and Cayman Brac showed marked growth,” the report stated.

The DoE and Reef Environmental Education Foundation also conduct an annual ‘Grouper Moon’ research project, which involves monitoring the annual Nassau grouper spawning, during which large numbers of the fish aggregate at specific sites during a full moon.
Researchers said, due to over-fishing during spawning, the species suffered region-wide stock collapse.

“By the 1980s, large aggregations had all but disappeared from the Caribbean region. Of the remaining aggregations, few contained more than 1,000 individuals, and the species is currently listed as critically endangered by the International Union for Conservation of Nature,” the researchers’ media statement said.

Read the full study:

https://www.pnas.org/content/early/2020/01/01/1917132117#abstract-2

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