Damselfish-assisted repair of wounded corals surprises scientists

A study published in Biology Letters found that yellowtail dascyllus damselfish help heal wounds on Pocillopora coral, with larger wounds recovering faster than smaller ones in the fish's presence. Researchers collected 72 identically sized corals from Mo'orea, French Polynesia, and tracked healing over 21 days with and without fish present, finding small wounds healed 38% faster and large wounds 55% faster when damselfish were around.

The study also found that coral-dwelling algae's photosynthetic efficiency held steady regardless of wound size when fish were present, but declined as wounds grew larger without fish. Researchers aren't yet sure whether the benefit comes from fish waste fertilizing the algae, improved water flow, or direct wound cleaning, and note damselfish themselves face pressure from the aquarium trade, where roughly 90% are wild-caught.

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