The marine waters of southeast (SE) Australia are one of a series of global ocean-warming hotspots. In it lies the Southern and Eastern Scalefish and Shark Fishery (SESSF), a multi-species fishery that catches a significant value of Australian Commonwealth-managed fisheries. Observations from the SESSF have indicated changes in the abundance and composition of the main finfish species. We conducted a marine ecosystem survey comparing the ecosystem including fish abundance of the commercial species, and community composition from an ecosystem survey conducted 30 years ago.
Spatial and temporal comparisons indicate that historically abundant species such as Eastern Redfish (Centroberyx affinis) and Silver Warehou (Seriolella punctata) showed lower catch rates than in the 1990s, while some pelagic-associated taxa, including Jack Mackerel and Redbait, exhibited higher contemporary abundances. Species also showed spatial shifts. Community analyses revealed that the community species assemblage has diverged strongly, suggesting ecosystem reorganisation.
These biological changes occurred alongside shifts in oceanography, plankton communities and trophic structure, indicating that warming-driven ecosystem reorganisation is propagating through multiple levels of the food web. The results suggest southeast Australian fish communities are transitioning toward a novel ecosystem state, with important implications for fisheries assessment, climate adaptation and ecosystem-based management in rapidly warming marine systems.