Something fishy about the night life of the Mariana Islands
For wet and wild nightlife, don’t look to Tumon, but to Tumon Bay. Surrounded by more than 100 km2 of coral reef, Guam’s shores are home to hundreds of tropical fish, crustaceans, mollusks and mammals, many of which don’t become active until after dusk.
Bring a bright light, a brave heart, and a full tank. A plunge into the inky black sea will reveal a landscape as far removed from the day’s rainbow reefs as some strange and alien planet.
Plenty more fish in the sea
At first glance, it may look like all the fish clocked out and left at the end of the day. Before you give up and go home, look between the cracks in the coral.
There, nestled in the digits of Acropora and the columns of Porites rus, triggerfish and squirrelfish rest just out of a predator’s reach.
In shallow areas abundant with diurnal clown fish, search the crevices for their sleeping symbiotic anemone. Not all fish are so careful. Neurotoxins make puffer fish extremely poisonous, allowing them to remain exposed.
Keep an eye out for the dog-faced puffers tuckered out in the sand like puppies.
No sleep for the hungry
Under the cover of night, the reef’s greatest and cutest predators begin their hunt. Seemingly immobile long spine sea urchins crawl out of their crevices, along with fat red and purple pencil urchins wriggling their spines in the water.
Enormous spider conchs, fist-sized cowries, and cone shells poke their foot out of their shell and make pedal waves.
Shrimps, spiny lobsters, and carpiliid crabs are also active. Wave your light over an expanse of seemingly empty coral, watching for the glow of shrimp eyes.
While small, colorful nudibranchs can be spotted during the day, large gold laced and lively Spanish dancers are also moonlighters. Shine your light into open-ocean to watch for swimming octopuses, sharks, and squid.
Stars in the sea
“There were stars in the sky and stars in the sea,” the old fishing legend goes, as told to the Star Lady, Pam Eastlick, by Jesse K. Lujan. One night, as a fisherman was casting his net, a shooting star fell across sky and landed in the ocean. Upon inspection, the fisherman fou nd pieces of the glowing star floating in the sea.
We now know this phenomenon as the bioluminescence produced by dinoflagellates. Under certain conditions, the microscopic creatures emit a light so bright it can be seen from shore, resembling a milky haze in the water. The plankton are also excited by a wave of your hand.
After covering the lens of your dive light, quickly move your hands back and forth, as the water flashes with blue green light.
Where to go
Although any healthy reef is bound to have an assortment of exciting nocturnal sights, the issue becomes access.
Unless you go with a guide, only chose sites that you have dove during the day and are already familiar with. The MDA dive shop runs guided night dives on Saturdays, meeting in the Piti shop at 5:30 p.m.
With an easy exit and a max depth of 25 feet, the Piti Bomb Holes Marine Reserve is also a great place to get over your fear of the dark.
In addition, a full moon can light up the shallow, sandy bottom of Cemetery Wall or San Luis like a spotlight. Now and then, cover your flashlight and navigate by the light of the moon.
Tips and lights
Specialized dive lights are not only waterproof, but are also much brighter than the average household flashlight. Like the regulator, PADI recommends carrying two lights, in case one should fail.
Choose one that is brighter than 150 lumens and portable.
Never turn off your light during a dive — if you want to see the dark, cover the light with your hand or press it against your body. It is also extremely easy to become separated in the dark.
Tie a glow-stick to every tank in your group and you will spend more time looking for sea critters and less time looking for each other.
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