Large-scale patterns in distribution of herbivorous fishes across the Great Barrier Reef
Project Leader: Dr Hugh Sweatman, AIMS
MTSRF funding has permitted analyses of an extremely detailed 17-year dataset compiled by the AIMS Long-term Monitoring Program, revealing meaningful patterns of richness and abundance of herbivorous fish species (parrotfish, surgeonfish and rabbitfish) in a standard habitat (the northwest reef face) on 93 reefs spread across the Great Barrier Reef. These patterns were observed both in terms of individual species and also in terms of functional groups of herbivores (scrapers, excavators, grazers/detritivores, algal grazers). Distinct cross-shelf patterns in total species richness were evident but these patterns were not consistent along the entire Great Barrier Reef: the highest total species richness in each shelf position was recorded in the Cooktown-Lizard Is sector, where total species richness varied little across the shelf, whereas in other sectors total species richness was generally least on the inner shelf reefs. Distinct cross-shelf patterns in total species abundance were evident but again, these patterns were not consistent for all sectors. Cross-shelf patterns in species richness and abundance varied among the functional groups of herbivorous fishes, but there was a consistent pattern in that each functional group was less abundant and less diverse on inshore reefs in the central Great Barrier Reef. There was also clear evidence of cross-shelf variation in the abundance and diversity of taxa performing certain functional ecological roles. This permitted the identification of shelf regions and sectors that appear to have low redundancy in functional ecological roles, and therefore potentially reduced resilience to change, namely the inner-shelf reefs of the Cairns, Townsville and Whitsunday sectors. By contrast, this analysis indicated that the Cooktown-Lizard Island sector appeared to have the strongest sector-wide functional resilience, with maximal functional richness and highest Reef-wide values for functional redundancy, species richness and abundance of almost all functional groups.
Report by CSIRO and the Australian Institute of Marine Science which outlines the objectives of Project 1.1.1 for Year 1: to develop indicators of protection levels for seabed species, assemblages and habitats for the GBR Zoning Plan in effect both before and after 1 July 2004, and identify the change in protection levels coinciding with the Representative Areas Program re-zoning.