MEPS 386:181-195 (2009)  -  DOI: https://doi.org/10.3354/meps08081

ABSTRACT: We analyzed stomach contents and muscle isotopic composition (δ¹³C, δ¹⁵N) of yellowstripe goatfish Mulloidichthys flavolineatus from a coral reef to investigate size-related dietary changes and resource or habitat partitioning. Juveniles (<12 cm total length [TL]), young adults (12 ≤ TL < 17 cm) and adults (≥17 cm TL) showed a high diet overlap, especially between juveniles and young adults. According to stomach contents analysis, M. flavolineatus widens its prey spectrum with increasing size from a common prey pool that includes polychaetes, tanaids and harpacticoid copepods. We observed a significant increase in δ¹³C values (from –17.1 ± 0.5‰ for juveniles to –10.7 ± 0.8‰ for adults), which were correlated to fish size. Adults (δ¹⁵N mean of 11.1 ± 1.8‰) were one trophic level above juveniles and young adults (7.7 ± 0.5 and 7.4 ± 0.5‰, respectively). These patterns of isotopic changes confirmed ontogenetic dietary shifts. However, trophodynamics can be influenced by physiological factors such as growth and sexual maturity. M. flavolineatus shift from a pelagic to a macrobenthic diet, which is equilibrated at the adult stage. Results from combined stomach contents (prey volume) and stable isotope analyses suggested a dominant contribution of polychaetes (macrofauna), possibly through selective feeding. Conversely, on the basis of prey volume and stable isotope data, meiofauna did not feature significantly in the diet despite their high abundance in stomachs. Two adult groups were distinguished based on their δ¹⁵N values (11.9 ± 0.8 and 7.8 ± 0.6‰), indicating possible stage-specific partitioning in habitat use inside the reef.

KEY WORDS: Yellowstripe goatfish · Ontogenetic diet shift · Stomach contents · Stable isotopes · Mixing model · Southwestern Indian Ocean