Tropicalisation of a damselfish (Gulf Damsel, <i>Pristotis obtusirostris</i> Günther 1862) in temperate Australian waters, with the first detailed observations of mass spawning

and dozens of nests per site. During nesting, males displayed reproductive behaviours including colour darkening, nest tending and egg aeration. These findings demonstrate successful reproduction well beyond the species' typical range and highlight accelerating tropicalisation within temperate reef fish communities.