'Upside-down underwater snow storm' is probably the description that matches best when it comes to coral spawning. During just a few nights per year, corals synchronously release their eggs and sperm and within a day the fertilized eggs develop into a 'Planula' larva, These get carried by currents until finding a suitable place to settle and form a new coral colony.
At the Banda Islands, we have witnessed this phenomenon in 16 different months since 2016. The main spawning months are April, October and November but we've also had observations in May and December. By now, we already understand well at what day and time it will happen. The best days are usually 5 and 6 days after full moon, the best time is 2-3 hours after sunset. In the last two months, we saw spawning on 4th October, 1st, 2nd and 3rd November (pictures above and below).
Table: Months in which spawning was observed (sadly note the Covid-19 gap;-))
2016 | 2017 | 2018 | 2019 | 2022 | 2023 |
Oct | Oct | Apr | Oct | Apr | Apr |
| Nov | May | Nov | Oct | Oct |
| Dec | Oct | Dec | Nov | Nov |
What is very unique is that several colonies even spawn in both main spawning seasons. This high reproductive output of the corals at the Banda Islands could be one reason for the high resilience and reef health here.
