Anemonefish sniff out bleached homes

As global concern grows for the Great Barrier Reef, a new study has highlighted the vulnerability of the iconic anemonefish in the wake of increasing coral bleaching events.

A paper published in Proceedings of the Royal Society B: Biological Sciences, co-authored by Dr Anna Scott, from Southern Cross University, has shown that while juvenile anemonefish could identify—through smell alone—if their potential home was bleached or healthy, they were inflexible in selecting other species as habitat.

The study, co-authored by Danielle Dixson, from the University of Delaware in the United States, tested five species of anemonefish and three host sea anemones to determine if these fishes were able to smell bleaching status of their host anemones. The fish were individually placed in an experimental chamber containing two streams of water flowing at identical rates but containing different chemical cues.

Dr Scott, who is based at the University’s National Marine Science Centre, said the results showed that all anemonefish were able to distinguish between bleached and unbleached anemones.

“Given the option of an unbleached or bleached host anemone, all anemonefish chose the healthy option. But given the choice between a bleached host anemone of their preferred host and another anemone species that was healthy, the anemonefish always chose the bleached host as their home,” Dr Scott said.

“Unfortunately, our research has shown that there is no flexibility in symbiotic relationship between the anemone and anemonefish. Anemonefish are behaviorally linked to one or a few species of anemone species and this means that bleaching events are likely to impact their populations.

“Juvenile anemonefish that select bleached homes are setting themselves up for bigger risk because we know that fish that go to bleached anemones have an increased risk of predation, and if the anemone home dies from bleaching, so will the fish.”

Found exclusively in the Indo-Pacific, anemonefish are symbiotic animals that only live in sea anemones, a close relative of corals that don’t have a hard skeleton. The anemone provides a home and protection, while the anemonefish provides food for the anemone.

“Understanding the negative impacts of declining habitat quality on these species is crucial given that bleaching events are becoming increasingly common. Not only are these species iconic, but they are also ecologically important and there are real risks to species survival if bleaching events continue to increase in frequency and severity,” Dr Scott said.

Photo: A bleached host sea anemone with resident fish (photo credit: J Stella).