The Yellowbar Angelfish (Pomacanthus maculosus)

Yellowbar Angelfish (Pomacanthus maculosus), Red Sea

by B. N. Sullivan 

If you dive near tropical reefs in the Indian Ocean or the Red Sea, you may encounter the Yellowbar Angelfish (Pomacanthus maculosus).  Often you will see them nibbling on a sponge,  or pecking at corals and algae-covered rocks.  In our experience, they don't seem to be fearful of divers, often swimming right up to have a look at us.  They are known to be territorial, so perhaps they approach divers to judge if they are friend or foe.

The adult of this species, pictured above, grows to a rather large size (for an angelfish!) -- up to about 20 in (50 cm).  The bright yellow patch on their flanks makes them easy to recognize.  Legend has it that the splash of yellow depicts a map of Africa.  That may be a bit of a stretch, but it accounts for the fact that an alternate common name for this species is Map Angelfish.  In any case, the exact shape of the blotch is unique to each fish, rather like a fingerprint.

The individual pictured above was photographed in the Red Sea, near Sharm el-Sheikh, Egypt.

The Ornate Butterflyfish (Chaetodon ornatissimus)

by B. N. Sullivan

Fishes in the Butterflyfish family (Chaetodontidae) are among the prettiest inhabitants of tropical reefs around the world.  This species, the Ornate Butterflyfish (Chaetodon ornatissimus) is particularly nice looking, we think.

The Ornate Butterflyfish is easy to recognize, with six diagonal yellow-orange stripes on each side of its creamy body, black and yellow bars on the face (including one that covers the eye), a gray patch on its forehead, and black 'trim' around its margins.  They are said to grow to a length of 20 cm (about eight inches), although most of the adult individuals we have seen are somewhat smaller -- usually about 15 cm (six inches).

C. ornatissimus feeds exclusively on live coral polyps, so you would expect to find them in coral-rich areas. They seem to favor coral polyps of the Pocillopora and Montipora genera.  (Here in Hawaii, we frequently see them pecking on Pocillopora meandrina.)

Juveniles of this species look like cute miniatures of the adults.  The juveniles can be quite shy, hiding in corals for protection.  The juveniles live as singletons, but once they reach breeding age, they find mates and form pairs.  In fact, it is unusual to see an adult of this species not accompanied by its mate.  Also, pairs establish a home range, so once you discover a pair of C. ornatissimus, you will likely be able to find them again in the same area time after time.

'Ornates' are an Indo-Pacific species, most commonly found in the central and western Pacific, from Hawaii to Australia's Great Barrier Reef.  Sightings have been reported as well around Christmas Island in the eastern Indian Ocean, and we have seen photos of the species taken in Indonesian and Malaysian waters.  They are quite common here in Hawaii. I photographed the one pictured on this page in Honaunau Bay, on the south Kona coast of Hawaii's Big Island.

Whale Sharks: The biggest fishes in the ocean

by B. N. Sullivan

There are lots of fishes in the sea, but there are none bigger than the Whale Shark (Rhincodon typus). These huge sharks live in tropical waters around the globe, and we have had encounters with them in many locations. Seeing these magnificent animals always is a thrill. Their size -- up to about 40 feet (12 meters) in length --  is impressive, and their grace is almost magical.

Unlike most sharks, Whale Sharks are filter feeders. They feed on krill, algae, plankton, and other small organisms suspended in the water. They take in large gulps of sea water, and sieve out the food as it passes over the denticles that cover their pharynx and gill plates. The water is expelled through the gills, while the filtered-out food remains and is swallowed.

No one knows for sure how long Whale Sharks live, but estimates of the creatures' natural lifespan range from 70 to about 100 years.  Whale Sharks do not reach sexual maturity until they are about 30 years old.  They are ovoviparous: that is, their eggs hatch inside the mother, develop without a placenta, and then emerge as live young.

Whale Sharks are curious and often approach divers and snorkelers to have a look, and will sometimes swim alongside them, but these  sharks are not known to be aggressive.  Encounters with these enormous but docile creatures are a joy for divers.

Here is a video, shot at Christmas Island in the Indian Ocean, that perfectly illustrates the excitement of divers who encounter Whale Sharks in the open water:

If the video does not play or display properly above, click here to view it on YouTube.

If you are interested to learn more about Whale Sharks, we recommend you have a look at this Whale Shark (Rhincodon typus) Issues Paper, from the Australian Dept. of the Environment, Water, Heeritage and the Arts; and the Whale Shark page on the National Geographic Web site.