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Experience a coral spawning session during a night dive! ~Ishigaki 4-Hour Spawning Documentary~



On May 19, 2016 (Thu), we were able to witness Midori-ishi (Acropora Coral) spawning at Ishigaki Island!
In the past few years especially, we prayed for the chance to see the coral spawning... Our wishes finally came true. The clear skies and seas of Kume Island were blue until the 2nd day, but they have returned back to winter conditions.
In recent years, in addition to being able to easily access images of coral spawning through Facebook and the Diving Shop's homepage in real time, I thought that if I dove into the sea on the scheduled spawning date I would be able to see it for sure, but I learned that I was terribly underestimating the situation...


On the day of spawning, timely arrival at Ishigaki

We traveled from Kume Island to Ishigaki on the 19th around noon, and were greeted by clear blue skies.
At Kume Island, we were faced with heavy rain and high waves due to the monsoon season, so when we arrived at Ishigaki, 'no rain' felt like a miracle in itself.
In addition, a series of miracles occurred as soon as we arrived, as the guide mentioned, 'Spawning has actually started yesterday!'
We were scheduled to go observe coral spawning at night, and although it wasn't in our plans to dive during the day, because we were unsure when it would start raining, we dove at 2 points upon arrival in order to get in as many diving sessions as possible.
We returned to the shop a little after 4PM to eat an early dinner and prepare for the spawning.


Midori-ishi spawning which spanned over 4 hours

■6:30PM
Departed Unarizaki.



There was a shiny luxury passenger boat from London parked a short distance from the port.
On this day, we decided to dive at the 'Northern Taketomi' point where the guide observed coral spawning the previous day (18th).
Night diving was not held at the Unarizaki Ishigaki store until last year, but the guide is a veteran when it comes to being present and witnessing coral spawning.
'Yesterday (18th), I found remarkable coral, and I think they will lay their eggs today.'
Our expectations rose.


On board, I will receive a spawning briefing. I was also lucky to catch the sunset from aboard the ship.

■7:30PM
The guide enters by himself and says, 'I wll go check if there are any coral holding eggs. I wll let you know if there are.'

■10 minutes later
'They are beginning to lay eggs! Hurry, Come!'
Wait, did we already begin?
We quickly entered the water with the equipment, but the first spawning had already ended.
A small amount of eggs appeared to be floating, but there was no major sense of excitement. After that, we searched for coral that had eggs.
Although the purpose was spawning, it was still the night sea.
We saw a Parrotfish put up its membrane and sleep, and on this day, there was a Blue-ringed Octopus sighting!!

A parrotfish that spreads its membrane and sleeps

It is rare to spot the Blue-ringed octopus in Ishigaki. The guide wonders if we will get to see more of them during night-diving in the future. For me, it was my first time seeing the Blue-ringed Octopus so I was excited just to see it, but in the words of our cameraman, 'The distinct blue rings displaying on the white body was very beautiful. The body color is usually more yellow.'

The highly poisonous Blue-ringed Octopus. You can die just by touching it, so please avoid touching it.

Before we knew it, 60~70 minutes had passed.
We received a signal from the guide that a certain coral was going to begin laying eggs, so we anxiously waited in front of it.
---Staying still at the location for 1 hour (About 2 hours passed since entering)
Upon entering, 30 of the 90~120 minutes were spent floating around because we were so tired...

I could not leave the coral that was about to lay eggs. I set my tank in the gap of a rock, and fought off drowsiness while conserving air.
However, the efforts were left void, and the residual pressure of the 9L aluminum tanks on backs were down to 30.
After about 130 minutes passed, we decided to change tanks.

It was already 9:45PM at this time. Return to the ship to replace tanks.
In car racing, the term would be pitting in.
While pitting in, we could see the cameraman's strobe light flashing from the ocean.
'Are you serious? It's starting now!?'
We hurried to enter, and headed to our previous location.
Then, you could see little orange eggs from multiple corals float up.
Wow.....



I had goosebumps all over my body, a physical sign of my excitement.
But the main event was just getting started.
When one coral finishes laying its eggs, the next coral will begin laying its eggs. After that, the next coral will begin to lay its eggs.
The time of spawning of one coral is not so long, but on this day, we were able to witness coral spawning for about 40 minutes.
When we use the term 'witness' (the birth of one's child), it may sound a bit humanistic, but this spawning process is really mystical. I have never witnessed the birth of so many lives at one time, so for me personally 'witness' feels like an appropriate term.

■10:50PM
The spawning settled a bit, so we received a signal to go back to the ship.
The path back to the ship was filled with plenty of large orange and pink coral eggs that were about 3mm. I experienced a mysterious space filled with life, which reminded me of a 'warp zone' scene from an animation I had scene before.
We were no longer feeling down about the monsoon. Coming during monsoon season for this spawning isn't so bad.



■11:30PM
Arrive at the store.
The spawning of Midori-ishi spanned over a total of 4 hours.


When is coral spawning conducted?

The spawning periods vary based on coral species, but in regard to Midori-ishi, there is data that it is in May after the spring tide around the time of full moon.
We asked the guide questions regarding coral spawning.
---Is the spawning period of the Midori-ishi (Acropora coral) always at this time of year?
'It is said that spawning usually occurs between the spring tide and full moon, but in Ishigaki, it occurs before the spring tide. In Iriomote, it occurs after the spring tide around the mid tide.'

---Doesn't the 'spring tide during the full moon' occur every month? Why May?
'We don't know the reason for that. It is different for each coral, and it is said that spawning only occurs once, but I have seen cases where it takes up to two months.'

---I have heard that spawning occurs when the water temperature is about 27 degrees.
'Actually, I've heard that it is not related. On the 19th, the water temperature was 27 degrees in the northern part of Ishigaki, but spawning did not occur. Strange isn't it?'

---You're right. is May the main spawning period?
'I am not sure you can say main, but for Midori-ishi, it is said to be May to June. For Kamenokikume-ishi, it is July~August. Plus, it is a type of coral that releases eggs all at once, so it also has a cool appearance.'

---Is that right? So if we want to see the spawning, we need to come back again next year? 'Oh, but at Iriomote it occurs around the mid tide after the spring tide, so maybe there's a chance we see the spawning during the Iriomote interview after this?'

---What! I am happy! What great news!

Thank you,

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