Diving Indonesia Periplus Adventure Guid. David Pickell

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      The blue ribbon eel, Rhinomuraena quaesita, is one of the most attractive moray eels. Young eels are black, and don't turn electric blue until they reach a bit over a half-meter in length. Bunaken group, Sulawesi.

      Most colonial tunicates are overlooked because they tend to be tucked away in dark corners. An exception are the marblesized, white-and-green grape ascidians, Diademnum molle, a common compound tunicate on shallow reefs in Indonesia. Diademnid tunicates have a single large inhalent opening, and many small exhalent openings around their globular tunics.

      Their green color comes from a symbiotic algae living within its tissues, much like the zooxanthellae of stony corals. The relationship between this tunicate and its algae is one of mutual dependency, neither party being able to survive alone. Diadem-num larvae even carry samples of the algae with them to ensure that the relationship is continued in the next generation.

      The Fishes

      Corals and other invertebrate animals can provide a lifetime of interest for a diver in Indonesia, but the fish are what really grabs one's attention. On most reefs, brightly colored and beautifully patterned fish are everywhere, darting among the corals or lying sedately in mid-water. It would be impossible in the space available here to offer a complete description of the thousands of fish species found on Indonesian reefs, so all that will be attempted is a brief survey. Consult "Further Readings" page 321 for more complete resources.

      Elasmobranchs

      Sharks and rays are elasmobranchs, and differ from true bony fishes by having a cartilaginous skeleton, only parts of which are calcified (e.g., the jaws of a shark). Gill structure—elasmobranch means "plate-gilled"— and other physical features differ between bony fish and sharks and rays, which are considered a more primitive form.

      Sharks. There are many species of sharks in Indonesian waters, but those most commonly seen by divers are the reef white-tip shark (Triaenodon obesus), the gray reef shark (Carcharhinus amblyrhynchos), and the reef black-tip shark (C. melanopterus).

      The reef white-tip shark grows to 1.7 meters, and is a thin, gray fish with white tips to its dorsal and tail fins. This is the most commonly seen shark on the Indonesian reefs. This small shark can be often be found hiding under overhangs.

      The gray reef shark grows up to 2.3 meters, and has a very dark trailing edge to its tail. Although this animal is known to be aggressive in some areas, it is not considered dangerous in Indonesia.

      The reef black-tip shark grows to 1.8 meters, and is pale gray or brown with distinct black tips on all its fins. This shark sometimes comes up into very shallow water on reef fiats and in lagoons to look for food.

      The largest fish extant is the whale shark (Rhincodon typus), a harmless animal that strains krill and small fish from the water. Growing to more than 12 meters in length (although specimens of 5-7 meters are more common), the whale shark is not a reef fish, although it can be found seasonally off some reefs in Indonesia.

      The only really dangerous sharks a diver might encounter on an Indonesian reef are the tiger shark (Galeocerdo cuvieri), a large—up to 5.5 meters—scavenger that sometimes comes up onto the reefs at night or in the late afternoon/These sharks, however, are very rarely seen.

      Rays. Structurally, rays are essentially flattened sharks. The stingrays have one or two stout spines at the base of their tail, which are their main means of defence. They will not normally be used against divers, although you should always take care to avoid stingrays while walking in shallow water.

      Stingrays are bottomfish, and have strong teeth which they use to crush shellfish. In areas where stingrays are common you may see large craters in the bottom, caused by their feeding activities. Perhaps the most common stingrays in Indonesia are two species of blue-spotted stingray: Taeniura lymma, which frequents coral rich areas, and Dasyatis kuhlii, which lives in sandy areas of disturbed reef, or between patch reefs. A much larger animal is the grey reef ray (Taeniura melanospilos).

      Not all rays are bottom-dwellers. The spotted eagle ray (Aetobatis narinari) cruises the reef edge looking for crustaceans. Eagle rays can reach 2.3 meters across.

      The largest ray, however, is the manta (Manta birostris). Like the whale shark, mantas are essentially open water fish, but they are regularly seen by divers in Indonesia. The manta СКАЧАТЬ