Dietary overlap among coral-feeding butterflyfishes (Chaetodontidae) at Lizard Island, northern Great Barrier Reef

This study documented the range of corals,\ud and other prey types, consumed by 20 species of but-\ud terflyfishes, which co-occur at Lizard Island, northern\ud Great Barrier Reef, Australia. Six species (Chaetodon\ud aureofasciatus, C. baronessa, C. lunulatus, C. plebius,\ud C. rainfordi and C. trifascialis) fed almost exclusively\ud on scleractinian corals, and a further eight species\ud (C. citrinellus, C. kleinii, C. lunula, C. melannotus,\ud C. rafflesi, C. speculum, C. ulietensis,and C. unima-\ud culatus) took a significant proportion of their bites\ud from corals. The other six species (C. auriga, C. ep-\ud hippium, C. lineolatus, C. semeion, C. vagabundus, and\ud Chelmon rostratus) rarely consumed coral, but fed on\ud small discrete prey items from non-coral substrates.\ud Coral-feeding butterflyfishes consumed a wide range of\ud corals. Chaetodon lunulatus, for example, consumed 51\ud coral species from 24 different genera. However, there\ud was up to 72% dietary overlap between coral-feeding\ud butterflyfishes, with 11/14 species feeding predomi-\ud nantly on Acropora hyacinthus or Pocillopora dami-\ud cornis. The most specialised corallivore, C. trifascialis,\ud took 88% of bites from A. hyacinthus. Chaetodon tri-\ud fascialis defend territories encompassing one or more\ud colonies of A. hyacinthus, and may have prevented\ud other species such as C. lunulatus from feeding even\ud more extensively on this coral. This study has shown\ud that coexistence of coral-feeding butterflyfishes occurs\ud despite an apparent lack of partitioning of prey\ud resources. While different coral-feeding butterflyfishes\ud were more or less selective in their use of different coral prey, virtually all species fed predominantly on\ud A. hyacinthus or P. damicornis

Differential use of shelter holes by sympatric species of blennies (Blennidae)

Comparative use of shelter use by three sympatric species of combtooth blenny (Ecsenius stictus, Glyptoparus delicatulus, and Salarias patzneri) was studied among micro-atolls in the lagoon at Lizard Island (14°42′S, 145°30′E), northern Great Barrier Reef, Australia. Blenny species used different sized holes; however, the average diameter and depth of holes used by the smallest and largest species differed by only 4 and 25 mm, respectively, indicating interspecific differences in suitable refuge can be very subtle. Both hole diameter and depth were positively related to total length of fish, suggesting use of holes relates to interspecific differences in body size. Total abundance of blennies was best explained by a general linear model that included either the number of holes or total habitat area on individual micro-atolls, predictor variables that were positively correlated with each other. However, the relative importance of variables differed among the three species, feeding area being most important for S. patzneri, feeding area and number of holes for E. stictus, and variance in hole diameter being the best explanatory variable for G. delicatulus abundance. The number of blenny species on a micro-atoll was best explained by variance in hole diameter, emphasizing the influence of refuge size variety in fish diversity. It is likely that subtle habitat partitioning, which relates to interspecific differences in body size, contributes to the co-existence of blenny species within the same microhabitat, but presence of holes is unlikely to regulate abundance of these fish