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Full Moon Whips Up Spectacular Coral Reef Spawning

July 26, 2018

It's Showtime! Divers will be headed to the Florida Keys National Marine Sanctuary in late summer to witness one of nature’s rare underwater spectacles off of Key Largo: sex on the stony coral reef.
One of the most spectacular but little known events along the reefs is the annual synchronized spawning of corals. That's right, corals do have sex to reproduce and to the lucky divers who are there it looks like a brilliant underwater fireworks display.  While there's no guarantee for the exact time and locations, the spawns are predicted on or soon after the full moons on August 26 and September 26.  
The only living coral reef barrier reef in the United States, the reef parallels the Keys island chain. Numerous dive shops and dive boat operations particularly in the Key Largo and Islamorada areas in the Upper Keys are scheduling coral night dives for the public. They fill up quickly. Boats typically depart between 8 and 9:30 p.m. and return to shore as late as 1 or 2 a.m.
The reproduction occurs when coral polyps release millions of eggs and sperm called gametes. As the spawning begins, tiny white, pink or orange spheres rise from the center of the polyps, first appearing as smoke. When illuminated by divers’ lights, all the gametes can resemble snow. Fish go into a feeding frenzy. However, the spectacular white excretion covers a broad geographic area to maximize chances of fertilization and overwhelm nearby predators with more food than they can consume.
This synchronized exchange of gametes ensures the survival of coral reefs, including boulder corals such as brain and star corals as well as the protected elkhorns and staghorns.
According to marine scientists, while corals use multiple reproductive strategies, nearly all large, reef-building species release millions of gametes once a year in synchronized mass-spawning rituals. These spectacular displays allow the stationary "animals" to mix genetically and disperse offspring over great distances.
"Broadcast spawning” enables the immobile animals to send their eggs and sperm into the water in massive quantities. When egg and sperm unite, the resulting larval-stage “planula" ascends to the surface to free-float in the current. Within a matter of days or even weeks, the planula settles to the bottom to grow into a polyp and form new coral reefs at the slow rate of about .4 inches a year.
What triggers the event? Scientists aren't sure, but appears to be a strong connection between the coral spawn and seasonal lunar cycles as well as water temperature and tidal and 24-hour light cycles. Cultured corals, the result of ongoing wild transplant efforts by Key Largo's Coral Restoration Foundation, also have been documented as spawning each year.
With the lunar cycle, scientists are able to predict when specific types of corals will most likely reproduce. For divers and snorkelers lucky enough to witness a coral spawn-- what many describe as an upside-down underwater snowstorm-- it’s a memory that will last a lifetime.
Seeing coral spawn is not a guarantee on the trip, but typically those participating on night dives have  experienced good success at viewing the spectacle. For a listing of dive shops, visit www.fla.-keys.com/diving
Florida maintains ban on harvesting goliath grouper.
Florida’s wildlife commissioners KO'd a move to allow anglers to catch and keep the endangered goliath grouper, the monster reef fish that have been protected in state and federal waters since 1990. The goliath grouper nearly disappeared in the 1970s.
"We’re not looking to have a harvest for the foreseeable future," Fish and Wildlife Conservation Commission Chairman Bo Rivard said after hearing from 56 speakers, of whom 55 were opposed.
Some anglers like the idea of catching such an enormous trophy. The giant of the grouper family, the goliath (formerly called jewfish) has brown or yellow mottling with small black spots on the head and fins, a large mouth with jawbones that extend well past its small eyes, and a rounded tail. It also has five dark body bands or stripes most visible on a young goliath.
This slow-moving, giant can reach 800 pounds and over 8 feet in length. The Florida record is a 680-pound goliath grouper caught off Fernandina Beach in 1961. The species had been targeted both commercially and recreationally since at least the late 1800s.
The harvest proposal grew out of complaints by some anglers that grouper populations had rebounded in some areas to the point that they were eating too much. They viewed the goliaths as a nuisance, and even a danger to some divers.
“Goliaths are recovering and becoming more abundant in parts of Florida, especially on artificial reefs,"  said Jessica McCawley, the Marine Fisheries Manager for the Florida Fish and Wildlife Commission. "While they opportunistically take snappers, and other groupers, these species represent a small portion of their diet while they primarily consuming baitfish and crustaceans. There are many unknowns in the life history and biology, especially maximum age, which makes it challenging to determine the status of the fishery.”
If Florida were to expand its catch and release rule to allow kills as well, it would be the first and only state in the United States.



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