Photo Observation of the Month of March - Gunther's Butterflyfish

We have now completed our fifth month of the Marine Biodiversity of Southern Sydney Harbour project and I'd like to congratulate user jenssommer01 for his Photo Observation of the Month of March, a Gunther's Butterflyfish (Chaetodon guentheri) from Parsley Bay. Gunther's Butterflyfish are rocky- and coral-reef associated fish, with juveniles usually seen at depths between 10 m and 30 m, and adults found at depths between 20 m to at least 50 m. Well done taking the plunge to get a glimpse of this species! In Australia, this species is recorded from southern Queensland to southern New South Wales (NSW) and is therefore adapted to subtropical and temperate environments, in addition to tropical climes.

It should be noted that at this time of year several species of exclusively tropical fish larvae have already made their way down south to recruit to rocky reef, rubble, and estuaries in the Greater Sydney region, helped by the warm, southward flowing conveyor belt system, the East Australian Current (EAC). Believe it or not, we live in a global hotspot for oceanic warming, and so some NSW scientists (e.g., Professor David Booth at UTS) have maintained 20+ year datasets to report new poleward observations of the juvenile stages of tropical reef fishes expatriating to temperate Australia. Average winter water temperatures above 18 °C represent some sort of magical threshold that allow these tropical vagrants to survive the wintery conditions in NSW. Ongoing citizen science initiatives, like Reef Life Survey and Redmap Australia, with your help, are also making massive progress in exposing these climate-driven range shifts.

This journal post was written by project leader and iNaturalist member, Dr Joseph DiBattista.