Butterflyfish (Chaetodontidae) have long since been used as bio-indicators by scientists to help determine the health of a coral reef system. The theory is that the healthier your coral colonies are the more corallivorous (coral eating) fish species you will see on your reef. There are 114 known corallivorous fish species globally and of these approximately 53 species are butterflyfish, how many can you name? They are known to feed on coral, at an average rate of 7 bites/min! (We tried to eat that fast and it got a little messy!)
Feeding styles of corallivores are classified based on the number of coral polyps that are eaten. The Spot-nape butterflyfish (Chaetodon oxycephalus) pictured above are faculatative corallivores, having a mixed diet that include some living corals. They have evolved long, fleshy lips that pluck out the individual coral polyps from the corallite cup they sit in without damaging the coral skeleton. This makes them a reef ‘browser’.
Many butterflyfish have a territory that they ‘browse’ over again and again. Like us re-visiting our favorite restaurants. But once a polyp has been eaten a coral can’t pop to the supermarket to replace it. You might be thinking that this continuous removal may reduce coral colonies over time, some studies (Cox 1994, Findley & Findley 2001), have instead reported a positive relationship between butterflyfish and their favourite coral species. As we start to see a change in coral cover from bleaching we will be keeping our eyes peeled for our resident butterflyfish to see what impact they might have on our healthy corals. Either bio-indicators of trouble or trouble makers themselves!
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