Nagelkerken, I., Van der Velde, G., Wartenbergh, S.L.J., Nugues, M.M., and Pratchett, M.S. (2009) Cryptic dietary components reduce dietary overlap among sympatric butterflyfishes (Chaetodontidae). Journal of Fish Biology, 75 (6). pp. 1123-1143.

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Abstract

This study used three different methods to ascertain dietary composition for 21 Chaetodontidae species co-occurring on a single fringing reef in Derawan Island, East Kalimantan, Indonesia. The combination of in situ feeding observations, examination of gut contents and stable isotope analyses was expected to identify previously unresolved prey items that contribute to dietary sep- aration. In situ feeding observations identified five species that feed predominantly on anthozoans (Chaetodon baronessa, Chaetodon bennetti, Chaetodon lunulatus, Chaetodon punctatofasciatus and Chaetodon speculum). Stable isotope ratios for these species, as well as for Chaetodon ornatissimus (for which no feeding observations were completed), were very similar and consistent with diets comprising mostly anthozoans. Feeding observations, however, showed that they mostly fed on different coral species, while the identifiable portion of their gut contents showed clear separation based on cryptic dietary components. For example, C. baronessa and C. bennetti appeared to ingest annelid worms during the course of coral feeding, whereas gut contents of C. punctatofasciatus and C. speculum were dominated by crustaceans. In situ feeding observations further identified the following groups: coral and bottom feeders, bottom feeders, sponge feeders and pelagic feed- ers, feeding on a wide variety of prey items such as Annelida, Crustacea, Cnidaria, Mollusca and macroalgae. Overall, many butterflyfishes had similar reliance on major prey items (e.g. anthozoans or polychaetes) but differed greatly in the minor prey items that they utilized. Partitioning of minor prey items may be important in reducing interspecific competition and facilitating coexistence of butterflyfishes on coral reefs.

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