According to many websites and books we have reviewed, witnessing coral spawning is a rather rare event, something that most ocean enthusiasts have on their bucket list but need a whole lot of luck to actually see. Well, I guess we were lucky, this weekend (3-5 April 2015) we were lucky enough to see several spawning events taking place, right here in Ballito and Salt Rock, in knee deep water!
Many Coral species will synchronize their spawning to ensure a better chance of fertilization taking place between corals, this is usually triggered by several different (and not well understood) natural indicators, the phase of the moon, length of day, water temperature and possibly even some sort of chemical response. In this case, it was the first full moon about a week after the equinox (days are getting noticeably shorter) - there were at least three different species of Coral spawning at the same time.
In some areas such as the Great barrier Reef, this synchronized spawning can produce what is known as a spawning slick. These can be meters wide and kilometers long, and often have a pink or brown tinge. Slicks have even been detected from space by satellite imagery! When an egg is fertilized, a tiny embryo develops within a day or so. The tiny baby coral is ready to settle after about five days, and drops down to the bottom. If it is lucky, it will find a good spot to grow for many decades.
Many of the online references also indicate that Coral spawning usually happens at night, in this case it was early morning. We don't know much else about this phenomena and would love it if anyone knows more about Coral spawning, what triggers it and similar information in South Africa to give us a shout.
A short video clip we managed to catch of the spawning
The fish certainly seemed to enjoy the free meal.