Photo of the Week: November 2009 Week 6

Hi Gang!

I am just back from a wonderful week of diving in Fiji with the crew of the Fiji Aggressor II. Before my trip Captain Steve told me that the Fiji Aggressor II is one of his favorites, and now I know why he was so enthusiastic about the location and the boat. We had a great trip!

In diving circles Fiji is known for its spectacular colors. Soft corals, sea fans, other invertebrates and fishes of every imaginable hue seem to be everywhere one looks, and with the opportunity to do quite a lot of the diving in relatively shallow water, the colors on Fijian reefs really pop.

We made three kinds of dives: bommie dives, wall dives and pass dives. Bommie is an Australian term that is used to describe mound-like coral reefs that rise high above the surrounding sea floor. In many cases the top of the bommies we dived rose to within 10 or 15 feet of the surface, and in some cases the top of the bommie was under less water than that. The sides of the bommies plummet quickly, thus creating what is often referred to as a mini-wall. The walls are covered with soft corals and sea fans, and the colors are absolutely stunning. Add a swarming school of anthias, a coral grouper, a banded sea krait or a school of jacks on the hunt and you have all of the ingredients that underwater photographers can hope for.

While the bommies are located inside of the outer reef wall, the walls are where the inner reef meets the open sea. Instead of dropping quickly to depths of 50 to 90 feet as is the case with the bommies of the inner reef, the sheer outer walls plummet to depths of a thousand feet or more in very short order. Pelagic species including dogtooth tuna, manta rays, hawksbill turtles, green turtles, eagle rays, and sharks cruise the walls. Most of the sharks are gray reef sharks but we saw at least one great hammerhead on five of our dives. Not many places where you can do that!

Then there are the passes, the natural cuts in the reef where currents run hard when the tidal exchange is strong. The passes are inhabited by schools of barracuda, big groupers and large gatherings of gray reef sharks. When the tide is incoming, clear water from the open sea floods the passes making conditions excellent for photographers. The currents make conditions good for the sharks and other large animal, and the combination is tough to beat.

One of Fiji’s more highly acclaimed passes is Nigali Pass off Gau Island, a small body of land located approximately 50 miles east of Fiji’s largest island, Viti Levu.  The sea floor at the seaward opening to the pass lies in approximately 100 feet of water, and the tops of the coral heads at the end of the pass where the water from the open sea spills into the lagoon during an incoming tide provide plenty of places to explore while doing a safety stop at dives end. Toward the middle of the pass there is a large coral head known to the crew of the Fiji Aggressor II as the bleachers. That is where divers go to position themselves and “tuck in” behind a little cover so that the sharks can be baited in as they are on some dives. For the baited dives the crew takes a few pieces of fish, ties them to the reef and the show begins.

I don’t really know how many gray reefs sharks were in the pass, but my guess is thirty plus. For the most part, the sharks seem to “know the game,” and they were pretty easy to get close to as we made our way to the bleachers. Once the bait was in place and ready to go, the sharks made a series of continuous passes often coming within a few feet of the bleachers as they made their way toward the food.

This week’s POTW is the best image I got of a single gray reef shark during my three dives in Nigali Pass. I was able to get within a few feet of the oncoming gray reef shark, balance my strobe light with ambient light, avoid background distractions and get a slightly upward shooting angle. Those ingredients gave me a pretty good chance to come up with a winning image!

The gray reef shark (Carcharhinus amblyrhynchos) is just big enough and “bad enough” looking to command our attention underwater and in photographs. Their taxonomic name is derived from the Greek words meaning, “sharp-nosed shark with blunt snout.” Strong black lines on the edge of their dorsal fins and tail are good identifying features to look for in order to help distinguish gray reef sharks from other sharks. Gray reef sharks reach sexual maturity after seven years at an approximate length of four and one half feet long.

Gray reef sharks have triangular-shaped teeth with very fine serrations. The small serrations are useful for slicing, cutting, ripping and chewing their prey. Documented prey fishes include butterflyfishes, coronetfishes, needlefishes, soldierfishes, moray eels and surgeonfishes. These sharks are also known to feed upon some crustaceans and cephalopods.

Gray reef sharks are among the most common sharks in many Indo-Pacific coral reef communities. They are often observed in reef channels and on reef faces, especially in areas where significant currents are common. Gray reef sharks have been seen in schools of 20 to 100 sharks. These groups often cooperate to ambush schools of small fish.  They usually approach the schools from below, although they have also been observed herding fishes into reef walls. These hunting groups are most often observed during the day. When night falls, these aggregations typically disperse with each animal moving out over the reef. At night gray reef sharks commonly enter shallow areas in lagoons. Rather territorial by nature, the average home range of gray reef sharks is believed to be one and one-half square miles. 

Gray reef sharks are viviparous, giving birth to live young. Females give birth to as many as six pups after a year-long gestation period. When born, the pups are approximately two feet long.

I hope you enjoy this weeks’ POTW, and I also hope that Captain Steve will put another trip together on the Fiji Aggressor II in the not too distant future! The Captain wasn’t able to make this trip, but I now know why he said he felt a little pang of jealousy when I told him I was going.

See you next week!

Marty