The Lemon Damsel Fish Experiment

Marine scientists conducted research into the Great Barrier Reef fish populations remind us that the tiny creatures in the ocean need protecting too. Professor David Booth and wife Gigi Beretta started an experiment on the lemon damsel fish that live off the coast of Australian islands in 1999. Booth, the President of the Australian Coral Reef Society, and his wife, a marine scientist who trained in the Caribbean, caught and tagged 532 juvenile lemon damsel fish in the One Tree Island lagoon off Gladstone in Queensland, and 322 in the waters of Lizard Island off Cape York. Yellow damsel fish are small, vivid yellow and found throughout the Great Barrier Reef. They have become a favourite in the aquarium industry. Booth and Beretta tagged the fish with an elastic polymer that showed up as a dark smudge under the fish’s skin. After they had been tagged they were released back onto the patch of reef where they would spend their entire lives.

The scientists have monitored them and have never found them more than two metres from their home. Booth says, “They live in a very restricted world.” The lemon damsel fish is one of the most common species of small colourful fish on the Great Barrier Reef, and the scientists only tagged a small portion of the population in their experiment. The goal of the experiment was to see how long such a tiny fish would last in such a dangerous environment. Booth returned to the same places every year since and has recaptured and examined the tagged fish for their physical health before being replaced. By 2004, only 5% of the original tagged fish remained at One Tree Island and none were sighted on Lizard Island after only four years. In 2009, only four were found, including one that at the time was declared the oldest known living wild damsel fish at a decade old. One last fish was caught in 2011, thought to be 12 years old. Booth says research such as this is a reminder that while many focus on the global scale threats like climate change, protecting individual locations is just as important.

“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.”