Detecting poleward migration of tropical fish species along southeast temperate Australia: can we measure tropicalisation of Sydney Harbour using historical museum data and other sources?

Prof David Booth1, Mr Mark McGrouther2, Dr Rob  Williams3, Dr Ash Fowler1,3

1University Of Technology, Sydney, Broadway, Australia, 2Australian=n Museum, Sydney, Australia, 3NSW DPI Fisheries, Mosman, Australia


Species distributions, their edges, and how these change through time are difficult to assess. Are field data accurate? Are multiple data sources required?  Here we assess historical change in marine species of fish reported for Sydney Harbour with the aid of museum records collected over the past century, citizen science “inaturalist”” and Reef-Life surveys, and project-specific surveys.  We examine the hypothesis that the long-term species accumulation curves for Sydney Harbour differ between species with temperate distributions and those with sub-tropical and tropical distributions, such that the proportions of sub-tropical and tropical species will increase relative to temperate species through time.

Range extension will be evaluated in two-ways: 1) through the frequency of occurrence following the initial collection time, with repeated collections after that time indicating higher likelihood of permanent extension relative to infrequent collections, and 2) using the body size of the specimens, coupled with known life-history and mobility of the species, to assess whether the occurrences of subtropical and tropical species in Sydney Harbour simply represent occasional extra-range dispersal and recruitment of juveniles, or an establishment of adult populations.


David Booth is Professor of Marine Ecology at UTS, and exPresident of the Australian Coral Reef Society.  He has published over 140 papers in reef-fish ecology, climate change and other anthropogenic impacts on fishes and fisheries, in the Caribbean, Hawaii, Great Barrier Reef, and studies how tropical fish travel down the East Australian Current past Sydney.  He researches fishes in estuaries around Sydney, the ecology and behaviour of threatened fishes such as seadragons, black cod and white sharks and the ecology of the deep sea.  He is also a strong advocate of sustainable fisheries and marine parks.

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