An international team of scientists suggests that damselfish and other coral fish from the northern part of the Great Barrier Reef may need to relocate hundreds of kilometers south, away from the Equator, due to ocean warming. Researchers claim that this is the only way to save the marine species because they cannot cope with the rapid temperature increase of their habitat despite having evolved to adapt to such changes.

In their study published in the journal Global Change Biology, the research team led by the ARC Centre of Excellence for Coral Reef Studies at James Cook University, analyzed how coral reef fish from Lizard Island on the Great Barrier Reef respond to increasing sea temperature. Researcher Jodie Rummer cites that they exposed groups of blue-green damselfish, also named Chromis viridis, to five different temperatures between 23 and 33 degrees for 27 weeks.

“One fish from each group was then placed inside two adjoining tanks where the water temperature can rise and fall. The fish were pretty smart. When it got too hot or cold, they moved to the other side,” Rummer explains. “Overall, they favored 29°C which was also the best temperature for a healthy metabolic rate. Anything higher than that and the fish needed 2-3 times more energy to cope.”

 

The fish that were restricted to 33 degrees Celsius lost 30 percent of their body weight. Some of the animals even died.

The study’s lead author, Adam Habary, says that the temperatures of their experiments were very realistic. Due to the warming oceans, the fish will be motivated to move to habitats with better environmental conditions.

Subsequently, the relocation of these fish could have some serious consequences on the area they would move to. Rummer predicts that coral reef biodiversity will be changed forever, and the Great Barrier Reef we know today will be different in the future.