Back when Bill Clinton was the president of the United States, UTS professor David Booth and his wife Gigi Beretta started an extraordinary experiment that demonstrates the ocean is as small as it is vast.
In 1999, Booth, who is the president of the Australian Coral Reef Society, and Beretta, who trained as a marine scientist in the Caribbean, caught and tagged 532 juvenile lemon damsel fish in the lagoon of One Tree Island off Gladstone in Queensland, and a further 322 in the waters of Lizard Island off Cape York.
They are small but beautiful animals – vivid yellow and found throughout the Great Barrier Reef. Yellow damsels are so spectacular that they are a favourite with the aquarium industry.
Each of the tiny young fish caught by Booth and Beretta was tagged with an elastic polymer that showed up as a dark smudge under their skin. After tagging they were released back onto the patch of reef where they would spend their entire lives.
“We have never found them more than two metres from their home base,” said Booth. “They live in a very restricted world.”
They are one of the most common species of small colourful fish seen on the Great Barrier Reef and the specimens that the scientists tagged and released were just a small fraction of the local damsel populations.
The goal of Booth’s experiment was simple: to find out how long such a tiny homebody can survive in such a dangerous environment, rife with predators and fierce weather.
Booth has returned to One Tree Island almost every year since and recaptured, measured and examined the tagged fish for their physical health before they were released again.
At the time of the first capture, each of the fish’s territories was also carefully recorded, which meant that Booth could return by scuba to the exact spot where each fish was released back in 1999.
While clouds of new, untagged, younger yellow damsels covered the reefs, by 2004 only 5% of the original tagged cohort on One Tree Island had survived and none were sighted on Lizard Island after four years.
In 2009 only four were found, including one that, at the time, was declared to be the oldest known living wild damsel fish. It had reached the grand old age of a decade.
Booth caught one last damsel, thought to be 12 years old, in 2011.
While Booth has not ruled out the possibility that a few surviving ancient damsel stragglers may yet be found he is calling the study complete and will soon publish his findings.
He says research such as his damsel study is a reminder that while much reef science and media focus is on issues such as climate change and the potential devastation of the reef by global-scale threats, protecting individual locations is also critical.
“Most of the organisms on the reef spend most of their lives within a very small area,” Booth said. “A lot of the time we look at the big picture and we overlook the small scale at which these organisms are actually living.”
He said it was critical that people did not get overwhelmed by the huge scale of climate change. A lot could be done to protect habitats at a local level by managing threats such as overfishing and pollution.
“These little fish remind us that we have to keep on chipping away at protecting the small areas and creatures as well as addressing the big issues.”
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