Marine Environments, Museum of Tropical Queensland

Update on Magnetic Island’s Giant Clams

This is the 2nd installment of a blog monitoring a bleaching event currently occurring in reefs off Magnetic Island, 14kms from the coast of Townsville in North Queensland

Unfortunately by 7 March, approximately two weeks since the last inspection, the bleaching of the giant clams along the snorkel trails of Magnetic Island had worsened.

In just a few short weeks, the number of giant clams (Tridacna gigas) on the snorkel trails that were bleached white had increased from two to five.

2nd blog update A
Partially (N5) and fully (N4) bleached clams at Nelly Bay snorkel trail, 7 March 2020.

A further eight were pale and/or blotched, a less extreme form of bleaching (e.g. N5, N6 & N7).

2nd blog update B
Partially bleached clams (N6 & N7) at Nelly Bay snorkel trail, 7 March 2020.

Only one of the fourteen giant clams had normal colouration (G2).

2nd blog update C
Bleached (G1) and unbleached (G2) clams at Geoffrey Bay snorkel trail, 7 March 2020.

Scientist from Queensland Museum and Magnetic Island monitored the clams again on 15 March 2020 and little change had occurred.

More updates will follow from the team monitoring their progress.

2nd blog update D Diver
Dr Rick Braley measuring giant clams (Tridacna gigas) at Lizard Island, Great Barrier Reef.
Giant clams can reach more than a metre in length and weigh more than 100 kg.

Written and Compiled by Dr Robyn Cumming, Collection Manager (marine) and Bryozoan taxonomist, Biodiversity & Geosciences Program, Queensland Museum and Dr Rick Braley, Aquasearch, Magnetic Island.