New James Cook University research finds that using the right toxin more quickly kills Crown-of-thorns starfish (COTS) and helps limit their ability to reproduce.
Lead author and JCU Professor of Marine Biology Morgan Pratchett has published new research demonstrating the best injection method to kill the problematic reef pest species and prevent them from spawning.
Professor Practhett's research team compared the effectiveness of vinegar and bile injection approaches.
"The bile injection was found to kill all the male starfish within 24 hours, so compared to vinegar, there was much less opportunity for those animals to spawn before they died," Prof Pratchett said.
"There was clear evidence that we should be using bile salts over vinegar, at least during the summer reproductive period."
COTS are native to coral reefs throughout the Indian and Pacific Oceans and eat live coral, with culling programs locally overseen by the Great Barrier Reef Marine Park Authority.
"Over the summer period COTS release all their eggs or sperm en masse," Prof Pratchett said.
"It seems to be initiated naturally by the one of the males starting to spawn. That cues the remaining starfish in the area to spawn at the same time … a single large female starfish the size of a dinner plate can produce literally millions of eggs.
"There's a concern that if you're not culling effectively, you just prolong the problem.
JCU biologist and research co-author Dr Peter Doll explained that when they injected female starfish, they would succumb and die, usually within 24 to 48 hours.
"We never saw any evidence that it induced spawning," he said.
"However, among the males, those animals that were injected did spawn. So there is a risk that culling these starfish during their reproductive period could initiate mass spawning."
With bile injections being expensive and sometimes difficult to obtain, Professor Pratchett's team are setting their eyes on optimising vinegar injections to control COTS.
"While climate change remains the reef's greatest threat, culling COTS is critical because it maximizes the opportunity for the reef to naturally adapt to changing environmental conditions," Prof Pratchett said.
"The next step is to increase the efficiency and effectiveness of the vinegar injection method by testing higher doses,
"But until then, it's critical that operators use the bile salts to avoid inducing spawning."
