On each sampling date (10-18 August, 10-18 September, 1-9 November, 1-4 December 1976, and 18-23 May 1977) during the 2-3 h of peak flow of the ebb and flood tides, fine-scale water speeds and directions from the surface down to about 23 m were measured; zooplankton was collected from 7 transects at stations located in front of (A), close to (B), and on top of the reef (C); and planktivorous fish were collected for gut content analysis from stations A-C and station D (behind the reef face).Gut contents were analysed from 240 individual fish from the 15 most common species (out of 37 species observed). Gut contents comprised copepods, larvaceans, salps, forams, miscellaneous crustacea, amphipods, gastropods, coral planulae, chaetognaths, polychaetes, pteropods, fish scales. Other mention is made to doliolids, heteropods, gastropod larvae, filamentous algae, fish eggs, and gelatinous material with reference to fish species in the text.Total numbers of zooplankton were recorded, 93 samples of plankton were processed for ash-free dry weights, and density (numbers m-3) calculated for 19 separate taxonomic categories in 60 separate plankton samples. Only 5 of these categories (Salps, Larvaceans, Copepods, Medusae, Forams) together with biomass are presented in the paper (the other categories showed no cross-reef trends or contained too few individuals for analysis). Densities for fish species that were not exceptionally aggregated or higly motile (Chromis, Caesio and Pterocaesio species) were determined at five depth intervals.The fine-scale water currents were measured at chest height on the fore reef face by releasing several milliliters of fluorescein dye and recording the compass direction of flow and the time the dye took to flow 1 m.