Reef specialists decline when corals suffer

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Scientists have confirmed that reef specialists suffer more when corals decline by studying damselfishes (pomacentrids) in the Great Barrier Reef.

The study by Shaun Wilson, Scott Burgess, Alistair Cheal, Mike Emslie, Rebecca Fisher, Ian Miller, Nicholas Polunin and Hugh Sweatman examined habitat use and specialization of pomacentrids, and determined which species are susceptible to declines in coral cover due to disturbance induced by crown-of-thorns starfish (Acanthaster planci).

Crown of Thorns starfish by Albert Kok, Creative Commons.

The authors used underwater visual surveys and then applied the data to mathematical models for their study.

They found that eight out of 20 adult pomacentrid study species and seven of 13 juvenile species displayed a preference for live coral, and that species with narrow niche breadths and high dependency on coral (Chromis ternatensis, C. atripectoralis and Pomacentrus moluccensis) consistently showed larger declines in abundance following coral loss than pomacentrids with wider niche breadths (Amblyglyphidodon spp. and Pomacentrus lepidogenys).

The authors conclude: ur study supports the hypothesis that habitat specialists are at greater risk due to disturbance than are generalists.

Crown of Thorns starfishAmblyglyphidodon curacaows, NOAA/NMFS/OPR, Creative Commons.

Analysis of changes to adult fish abundance following coral decline found that highly specialized coral-associated pomacentrids consistently declined in abundance, while the response from generalist habitat-users was more variable and may relate to the severity of the disturbance.

A high proportion of pomacentrids are closely associated with live coral, although the type of coral they associate with varies among species and often changes ontogenetically.

Importantly, associations with live coral were especially high among juveniles, suggesting that this is a life-history phase more vulnerable to coral loss, which may have serious consequences for future adult stocks.

The study is published in the latest issue of the Journal of Animal Ecology.

For more information, see the paper: Wilson, SK, SC Burgess, AJ Cheal, M Emslie, R Fisher, I Miller, NVC Polunin, HPA. Sweatman (2008) Habitat utilization by coral reef fish: implications for specialists vs. generalists in a changing environment. Journal of Animal Ecology 77, pp. 220"228.