In my article, “2010, the International Year of Biodiversity – Clownfishes.” under the section entitled, “Can clownfish adapt to climate change?” there was a mention that one species of clownfish had recently been shown to use soft corals as an alternative habitat, something previously only seen in captivity. This is referenced to Arvedlund, M., and Takemura, A. (2005) Long-term observation in situ of the anemonefish Amphiprion clarkii (Bennett) in association with a soft coral. Coral Reefs 24, 698-698.
Having managed to track this paper down I can now expand on the reference.
Between May 2003 to December 2004, during the course of 37 daytime snorkeling surveys between the hours of 11.00 and 18.00, an adult Amphiprion clarkii was observed at a depth of 1 m, living in the same soft coral, a Lobophytum species of around 90 cms in diameter.
This took place in the Ryukyus Archipelago in southern Japan, at the southernmost local reef of Sesoko Island. This area was seriously affected by the global bleaching event of 1998; in the aftermath of this event several species of host anemones disappeared while the surviving anemone species declined. At the time of the paper, 2005, the anemone population had yet to recover.
Although anemonefishes are known to adopt a wide range of soft corals in captivity, this form of behaviour is almost unknown in the wild.
All 28 known species of anemonefishes have an obligate symbiotic relationship with at least one of ten species of anemones belonging to the families: Actiniidae, Stichodactylidae and Thalassianthidae. There tend to be species specific associations which range from Premnas biaculeatus, Maroon Clownfish, associating with a single species of anemone, Entacmea quadricolor, Bubble-tipped Anemone, to Amphiprion clarkii which has been found in association with all ten species of known host anemone.
From personal observation, the main author of the paper, reports that A. clarkii will often take shelter away from its host anemone when pursued by a potential predator whereas most other anemonefishes, take refuge in their host anemone. The paper ends by speculating whether the ability of A. clarkii to associate with a wide range of anemones and, as has now been observed, with corals might go some way towards explaining why it’s the most widely distributed species of clownfish.
Other than the fact that Lobophytum species soft corals are amongst the most toxic of corals, something that might deter predation by fishes and aid the coral in competition against other corals, this species appears to offer little in the way of protection for a clownfish. This leads me to further speculate whether A. clarkii is evolving away from its obligate association with host anemones or to question if this is just one fish that has been unfortunate enough to lose its host yet been lucky enough to survive for so long in the absence of an anemone.
More reports of clownfishes, particularly A. clarkii, are required before we can come to any conclusions.