Scientists dive off the coast of Little Cayman island in the Caribbean Sea equipped with video and audio technology. They’re recording the endangered Nassau grouper fish sing to each other.
Scripps Institution of Oceanography ecologist Brice Semmens measures the magnitude of these songs to count how many fish there are.
“We stick hydrophones, which are passive listening stations, at the spawning sites. It turns out fish, like birds, often sing,” Semmens said. “We can use that singing that they do to provide an index of the abundance of the population. The more singing there is, the more fish there are.”
This listening strategy is one of many tactics Scripps researchers and scientists from the Shedd Aquarium in Chicago have been using to count the highly endangered Nassau grouper.
This species, found only in the Caribbean Basin, has been on the brink of extinction for decades.
The Cayman Islands government discovered the population about two decades ago and decided to create a marine protected zone where the fish were found. The zones prohibited fishermen from hunting this species. The government teamed up with Scripps researchers and other scientists to determine whether this strategy was actually working.
“The problem with marine-protected areas is that outside of those areas, fishing is allowed,” Semmens said. “In efforts to tag fish and find out where they were coming from, we found out that every single reproductive-aged individuals in the population went to the spawning site.”
Those mating sites are outside those protected areas, so fishermen continued to catch these fish.
But with scientists’ help and efforts tracking these fish, the Cayman Islands government changed their conservation policies to make this species protected during their mating season.
In the last decade, the population of Nassau grouper increased from 1,000 to 7,000 fish.
“For the species of Nassau grouper, nobody has ever demonstrated recovering the population following overfishing,” Semmens said. “We’re the first to show that happen.”
Semmens says researchers plan to continue their tracking efforts. He also says the success shows how science can effectively shape government policies.
