Standard Talk (15 mins) Australian Society for Fish Biology Conference 2022

Long-term changes in the reef fish communities of the Great Barrier Reef Marine Park (#29)

Daniela M. Ceccarelli 1 , Michael J. Emslie 1
  1. Long Term Monitoring Program, AIMS, Townsville, Queensland, Australia

Estimated at over 1,600 species, the GBR’s reef fish community is diverse, productive, relatively intact and of immeasurable value to the functioning of the ecosystem and to the nutrition and enjoyment of Australian people. The AIMS LTMP has monitored these fish communities for 30 years across the entire latitudinal and cross-shelf span of the GBR, on representative reefs of both fished (blue) and no-take (green) zones. Over this time period, reefs in different shelf positions (inshore, midshelf and offshore) have shown distinctive temporal dynamics in overall fish abundance and species richness. The largest influence on fish assemblages have been disturbance events, while fishing impacts are restricted to a few primary (Plectropomus and Variola spp.) and secondary (e.g. Lutjanus spp. and Lethrinus spp.) target species. These species have benefited from no-take zones in that both their abundance and biomass are higher than in fished zones, with increasing evidence of spill-over into blue zones. Fish species composition varies significantly according to shelf position, with different species representing each functional group across the inshore-offshore gradient. Species composition also varies by latitude, but has remained relatively stable in most sectors over the monitoring period. Inshore reefs have a distinctive and less varied species assemblage than midshelf and offshore reefs, but remain productive, with green zones providing adequate protection to target species and acting as a buffer to disturbances. We explore the relationships between the fish community and elements of the benthos, consider the inclusion of novel community metrics, and discuss the consequences of changes to the trophic composition of fishes on the GBR.