By Walt Stearns
It was well into the night, and black as pitch. We could actually see the stars through the clear waters overhead, and our dive lights seemed insignificant against the steep drop off below. The location was the eastern end of Penama Island in the central region of the Vanuatu island chain. We didn’t mind the dark, and in fact had planned it that way, purposely selecting a night during a new moon phase to further increase our chances of finding one of the ocean’s oldest living cephalopods, the Chambered Nautilus. Our quest didn’t take long, less than eight minutes into the dive, the first pair was spotted just below the crest of the wall at depth of 60 feet. As the night went on, we continued to find them shallower and shallower, to the point of seeing them on top reef shelf in as little as 16 feet of water.
Location: Vanuatu, Penama Island - Date: Aug. 14, 1992
If you are ever fortunate enough to encounter a Chambered Nautilus on a night dive, you will be sharing the water with a true living fossil. As a cephalopod, the Nautilus is in the same class of mollusks as octopuses, squid and cuttlefish. This group dates back more than 500 million years, and was once the dominant form of life in the ocean.
Over the eons, other cephalopods transformed their armoring shells into internal beaks, and became masters of camouflage, concealment and evasion. The Nautilus, meanwhile, kept its protective hard shell and has remained virtually unchanged for the past 450 million years. They also grew more tentacles. Rather than the eight to 12 found on their soft-bodied cousins, they have 90. And though the eyes are one of the nautilus’ most striking features, they don’t work well, as they have no lenses. For hunting, this animal relies much more on a pair of rhinophores (just like nudibranchs), which detect chemical changes in the water to help find food in the dark.
And it is in the dark where the two surviving genra – the Palauan Nautilus and the Chambered Nautilus – spend their time. The live in deep costal waters of the Indo-Pacific, spending the daylight hours at depths of 300 to 500 meters (1,000 to 1,600 feet), then rising to hunt on coral reefs during the night.
Fishermen have learned to capture nautilus by setting traps at depths from 50 to 100 meters (160 to 320 feet). This is usually done to harvest the shells for ornamental sale, but on the deep drop offs in Palau, Papua New Guinea, and Northern Solomon Islands, it’s also done to provide photographers with a subject.
One might think that catching and releasing an animal after a photo op is better than killing it for the shell. But in reality, the sudden depth change, combined with exposure to bright sun light and warmer water temps (nautiluses generally avoid water temperatures above 25°C) places a serious stress on the animal, and many don’t survive the release.
The one place where it’s possible to photograph or observe a Chambered Nautilus without doing harm is in the Southern Melanesian Island Group, between New Caledonia and Vanuatu. Here, Chambered Nautiluses can be found at night to depths as shallow as 5 meters (16 feet).
The reason for these shallow-water appearances is not known, though some scientists speculate that it is because the surface water temperatures in these southern hemisphere habitats are cooler than in equatorial habitats. One thing is certain, make a night dive the edge of a reef with a deep drop off to 100 meters (330 feet), as I have done off the reefs in around the island of Espiritu Santo in Vanuatu, with little to no moon, and you are almost assured of success.
Because nautiluses are highly light sensitive, I would advise limiting dive light use to quick, periodic sweeps when hunting. Once a nautilus is found, make your photo encounter brief to avoid stressing the animal too far, perhaps three or four shots before moving on to the next Nautilus. When there is one, there are often several more in the area.
Photo information: Photos taken (August 1992) in Vanuatu with Nikon F4 and Nikon 60mm macro f.2.8 lens. Lighting provided by two Sea & Sea YS-200 strobes set at half power with camera settings 1/60 sec. and aperture values at f11 and 16 with Kodachrome 25asa film.