Reef Report for Thursday, November 15, 2001
Coral Spawning Happens Soon!
This year we have had difficulty in predicting exactly when the corals of the Cairns section of the Great Barrier Reef would synchronize their spawning. This one massive night of sex happens only once a year, between the third and sixth night after the November full moon.
The problem this year is that there are two full moons in November (the second full moon in the same month being called a blue moon).
Thankfully, the corals surrounding Magnetic Island spawn exactly one full moon before the Cairns section does. These did not spawn in October, so then we knew that the reefs off Cairns would spawn in early December.
Many local operators will conduct special coral spawning trips. It is a fantastic sight to see. Millions of animals pass out packages containing both eggs and sperm. Other coral species have separate sexes, the females milking out eggs while the males ooze out sperm. Some species keep their eggs inside their bodies. becoming pregnant by swallowing the sperm that has already been sent into the ocean. The event is often described as appearing like snowfall under the water, only the snow is falling upwards, it is an amazing underwater experience.
It is not only the corals that are in on the action. Crustaceans, molluscs, fishes, cucumbers etc, all time their reproduction at around the same time as the corals. The Titan triggerfish are defending their nesting sights at this time. The female lays many batches of eggs between November and February. Twenty-four hours after laying her eggs, she blows the juveniles out to sea to colonize on other reefs. During these nesting periods, she is phenomenally aggressive and divers should keep their distance from their nests. In between laying each batch she becomes passive again.
Reef Teach run nightly multi media presentations by Marine Biologist Paddy Colwell, on the Great Barrier Reef should you wish to know more about this fascinating time out on our oceans.
The weekly reef report is written by Sue-Anne Chapman of Pro Dive Cairns, who compiles them from the many conversations she has with divers, dive instructors, captains, and others in the Cairns dive community. The report is published weekly in the Cairn Post, the local daily paper and appears here thanks to the courtesy of Pro Dive Cairns.
Index of all reef reports.