Diving Indonesia Periplus Adventure Guid. David Pickell
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Название: Diving Indonesia Periplus Adventure Guid
Автор: David Pickell
Издательство: Ingram
Жанр: Биология
Серия: Periplus Adventure Guides
isbn: 9781462909155
isbn:
Wrasses undergo sometimes dramatic color changes as they pass from juveniles to adults. Many of these predators on worms and small crustaceans bury in the sand at night to sleep, or dive into the sand to escape predators.
Most familiar to divers is the blue-streak cleaner wrasse (Labroides dimidiatus), which set up stations to clean small parasites and pockets of decay from the skin, mouth and gills of larger reef fish. Some wrasse act as cleaners only when young (for example, the colorful lyretail hogfish, Bodianus anthoides).
The largest of the family is the Napoleon wrasse (Cheilinus undulatus), which can reach 1.8 meters. This is one of the largest fish a diver will see on many dives. These stately animals, also called the humphead wrasse, have a prominent forehead and formidable-looking snout and cruise the outer edge of the reef in loose groups, with one large male and a few smaller females.
The Napoleon wrasse, or humphead wrasse, Cheilinus undulatus, is the largest wrasse and—at up to two meters — often the largest fish of any kind one will see on a given dive. This predator on crustaceans, gastropods, fishes and echinoderms is usually a solitary rover, but sometimes a pair or a small "squad" will be seen. Australians call this fish the Maori wrasse.
Parrotfish, The parrotfishes (family Scaridae) are among the most important herbivores on the reef. They get their name from their bright colors, curious flapping "flight" (much like wrasses), and their strong, birdlike beaks, which they use to scrape algae and other living matter from rocky surfaces. In so doing they inevitably take in great quantities of coral rock. This is ground down by powerful sets of teeth in the throat so that the organic material can be more easily digested, The waste product of the feeding activities of parrotfish is coral sand—a major component of Indonesian beaches especially on the offshore islands.
Parrotfishes are protogynous hermaphrodites that undergo a series of color changes with age and sexual status. Primary phase parrotfish—whether males or females—are exceedingly difficult to identify, all being relatively drab grey or rust-colored. The terminal males are striking, however, usually green with bright markings, particularly around the cheeks and eyes, In most species the primary phase is made up of mixed males and females (diandric); in others the primary phase is all females (monandric).
One notable exception to this pattern is the bumphead parrot-fish (Bolbometopon muricatum). All bumphead parrotfish (males, females and juveniles) are a dull green in color. Although parrot-fish have popularly been considered coral-eaters, they are chiefly herbivores, scraping the reef surface to extract the algal turf, not to eat coral polyps. The bumphead parrotfish is an exception, and feeds for the most part on living coral. They are massive beasts which grow to over a meter in length and travel along the reef in groups looking for all the world like squadrons of army tanks, leaving clouds of coral sand in their wakes. Sometimes their crunching can be heard Underwater.
They should not to be confused with the Napoleon wrasse (see above), a superficially similar fish. The bumphead parrot-fish has a more rounded head.
At night, parrotfish secrete a transparent cocoon of mucus in which to- sleep. At first glance such a fragile structure would seem to offer little protection against predators, but at night, most predators hunt with their sense of smell not their eyes, and the cocoon is an effective defense against this.
Barracudas. These familiar fish (family Sphyraenidae) are one of the most important predators on the reef but their reputation for ferociousness is exaggerated. Despite their formidable teeth in Indonesia they are not known to attack divers. Smaller species of barracuda often gather in school during the day, sometimes numbering many hundreds of individuals In contrast, large barracudas (which may grow up to1.7meters)tend to be solitary. Such giants may be quite old, so are less likely to be seen near heavily populated areas where there is lot of fishing pressure.
The bumphead parrotfish, Bolbometopon muriaticum. This, the largest parrotfish, is also one of the few true coral feeders. With its impressive fused "beak" it can crunch on corals like they were pretzels. It is sometimes confused with the Napoleon wrasse, but a comparison of this photo with the one on the previous page should make clear the physical differences: between them.
Blennies. These little fishes (family Blenniidae) often go unnoticed by divers They are most abundant in the shallows, and can:also be found on back-reefs and in murky estuarial waters. Most are not very colorful. Some have interesting "faces," although these are only really visible to the macro lens.
The mimic blenny (Aspidontus taeniatus) mimics the color and even the movements of the blue-streak cleaner wrasse Labroides dimidiatus. However, instead of cleaning parasites from the larger fish the mimic blenny bites off a tender chunk of scales and flesh, and then beats a hasty retreat.
Dartfishes. One group the diver will notice, because of their striking colors and their habit of hovering in small groups above the coral sand, are. the firefishes (Nemateleotris: spp particularly N. magnifica, a beautiful fish with a greatly, elongated dorsal fin which it flicks in nervous little movements.
Gobies. These fish (family Gobiidar) are small usually dull-colored, and often remain hidden In crevices and the branches of coral. There are many hundreds of species and perhaps 100 genera in the Indo-Pacific: making them the single most successful family on the coral reefs. Identifying these fishes is very difficult, and there are probably hundreds still undescribed.
Although not reef-dwellers, the curious mudskippers (Periophthalmus), which can be found In Indonesia on the brackish mudflats around mangrove swamps are also gobies As long as their gills and skin remain wet, these small brown fish can hop about on land.
Related to the gobies are the little dragonets. These are found in weed area and sea grass beds as well as the reef itself. Perhaps the most spectacular is the mandarinfish (Synchiropus splendens), with a pattern that could have come off a bright paisley silk tie.
Surgeonfish. The surgeon-fishes and tangs (family Acanthuridae) are a particularly important group of herbivores. They are sometimes seen in singly, in shallow Water over coral flats. Since single grazei are often chased by damselfishes protecting their territories, surgeonfishes sometimes form large feeding aggregations.
Despite their apparently destructive feeding habits, herbivorous fish are of immense value to the coral reef community, By breaking clown hard-to-digest plant material they make the nutrients in it available to other animals. Furthermore, by limiting the growth of plants they may actually enhance that of corals. Without grazing, the plants would grow to such an extent that they would soon cover the reel making new coral settlement virtually impossible.
The surgeonfish family includes some of the most exquisitely patterned and colored of all reef fishes. But one feature that is common to all is that they all have one or two pairs of scalpel-like blades on the Sides of their tails. These give the family its name and can inflict serious cuts if the fish are handled carelessly.
The orangespine unicornfish (Naso lituratus) with its bright orange spots warning of its spines; the hepatus tang (Paracanthurus hepatus) with its electric blue and black body, and the clown surgeonfish (Acanihurus lineatus), oraiige-and-blue striped, are just a few examples.
Moorish idol and Rabbit-fishes. The Moorish idol (Zanclus cornutus) and the rabbitfishes (Siganus) are close relatives of the surgeoniishes. The Moorish idol is for many people the quintessential reef fish; with its bright, contrasting yellow, white and black color, prominent snout, and long, СКАЧАТЬ