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Coral Spawning Watch | Maui.Net - All Things Maui
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May. 23, 2008 by Michael Elam

Coral Spawning Watch

The Hawaiian creation chant places the origin of life at the sea, beginning with a coral polyp. Springtime is the beginning of the yearly coral spawning ritual.

The signals are subtle. First, the water temperatures begin their gradual rise as the season changes from winter to spring. Next, a fat full moon droops through the heavy clouds of a tropical May spring night. Below the ocean's surface, coral polyps begin to swell slightly.

Coral spawning is an amazing thing to observe. During this annual event, the wonders of the reef are even more amazing. Several species of reef fish feed on the spawn and predators such as eels and jacks take advantage of the unusual reduced visibility conditions hoping to feed on the smaller fish, and an entire food chain can be observed in a microcosm. Catching sight of coral spawning in the wild is in many ways a guessing game, but researchers say that observers stand the best chance with certain species on specified dates and times.

Then after the spawning and fertilization occurs, in the grasp of tides and currents, the tiny new coral embarks on a grand voyage that can last for months and carry it hundreds of miles from its origin. If this speck of life somehow survives the ever-hungry mouths of plankton-pickers, filter-feeders, and jellyfish, it will one day mysteriously sense a suitable hard surface below, settle, and begin producing a tiny calcium skeleton – the genesis of a great coral colony that could live for hundreds of years.

I set out with Pauline Fiene and the crew of Mike Severns Diving for Molokini Crater at the earlier-than-usual time of 6:00 AM. According to Pauline's carefully documented notes and the observations made by her and her crew over many years, the Cauliflower coral was expected to spawn at 6:45 AM on Wednesday, May 21, exactly two days after the full moon.

Once we arrived at Molokini's Reef's End we wasted little time entering the water and indeed, literally the moment we reached bottom we watched an Antler Coral head spew tiny pearl-like eggs and smoky sperm into Molokini's clear tropical waters. Then nearby another Antler coral began, then another and another.

According to Pauline, each species of coral conducts kind of a "chemical conversation" with each other and based on the time of year, the length of time after a full moon, and at a specific length of time after the sun's morning rise their biological alarm clock sets them all off simultaneously! Different coral species reproduce at different times and mostly at night but some can be observed during daylight hours.

These spectacular "broadcast" spawning displays allow these stationary animals to mix genetically and to disperse their offspring over great distances. It is also believed to maximize the chances of fertilization, and at the same time overwhelm predators with more food than they can possibly consume!! Unless you see it with your own eyes it is hard to believe that such a small animal is able to reproduce in such a huge volume.

And the fish know that food is coming too! It was fascinating to watch the Pyramid Butterflyfish in particular hover over a coral just before it began to spawn. There is obviously some type of signal the fish pick up that we humans cannot.

Several minutes later, the Antler coral spawning stopped and our group continued the dive observing moray eels, jacks, white tip reef sharks, and all the other common creatures found at Molokini.

And then, the main event began! What seemed to be the entire reef simply exploded in spawning instantly reducing visibility from Molokini's usual 150 feet to near zero!! It was like an underwater snow storm had shrouded the reef in a complete fog of this stuff! In another 10 minutes or so the event was over. Arrive a few minutes too late or too early and you miss it completely.

When the dive ended as we returned to the boat, we experienced a very briny, fishy smell of the spawn as much of it reached the surface. Another one of nature's miracles.

All photos provided courtesy of Pauline Fiene.

About the Operator
For those planning to do some boat diving while on the island Mike Severns Scuba Diving is owned and operated by Pauline Fiene, who knows the Hawaiian waters and sea life like no other. Pauline has a degree in biology and she and her divemasters are passionate about sharing their knowledge with other divers. She is the co-author of several diving books including "Molokini - Hawaii's Island Marine Sanctuary," has studied Hawaiian marine life for fifteen years, and has personally discovered several new species of marine life. Her knowledge of the unique species found only in Hawaii is tremendous, and what I appreciate most is that Pauline personally makes sure you see it (as Divemaster). Dive sites are chosen in the morning depending on the interest of the divers and ocean conditions. PILIKAI is a spacious 38 ft. Munson Dive Boat which takes two groups of six divers.

Dive stats:
Location: Molokini Crater at Reef's End
Maximum Depth: 75 feet
Bottom Time: 52 minutes
Visibility: 150+ feet (except when the coral spawning occurred!)
Water Temp: 75°


"Fascinating Mike! I was especially interested to hear about how the butterfly fish reacted. Thanks for the great article. Aloha, Rachel"

Posted by ScubaSista on May. 27, 2008

"Hi Mike, Thanks so much! What a great opportunity to see the coral out in the wild. See you on the water. Patricia Maui Canoe Club"

Posted by Patricia C on May. 25, 2008

"Awesome post Mike! I'm glad Maui Net got the RSS feed to work! I have you in my Google Reader! -Liz"

Posted by footesea on May. 23, 2008

"This is a great blog with outstanding photos and lucid, well-written accounts. Bravo! from Dr.B of Mana'o Radio"

Posted by ManaoBee on May. 23, 2008

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