donderdag 22 november 2012
Porcupinefishes are on every dive site around the Gili Islands. You will find the for example when you are diving North Gili Air, on Hans reef. But is the Porcupinefish the same fish as a Puffer fish? Porcupinefishes are similar to puffer with regards to their ability to inflate by drawing water into the addomen. They have additional protection in the form of sharp spines on the head and body. These are either three rooted or non movable as seen in the burrfishes or two rooted and erectile in Diodon. In the genus Lophodiodon both types of spines are evident on the same individual. Typically the spines of Diodon lie flat against the body with their tips directed posteriously, but if theatened the body is expanded and the spines are erected approximately perpendicular to the body surface, forming an obvious deterrent to potential predators. Porcupinefishes and burrfishes further differ from puffers in having broader pectoral fins, in lacking a median suture on their dental plates and having larger eyes. Most are nocturnally active, usually hidden in caves or beneath ledges during daylight hours. Their strong dental plates and powerful jaws are well suited for crushing the hard outer shell or test of sea urchins, gastropod molluscs and hermit crabs as well as exoskeleton of crabs. Care should be exercised when handling these fishes because of their obvious spines and capability of inflicting severe bites. They are also reports of poisoning due to people eating diodontid fishes presumably from tetrodotoxin but they can also cause ciguatera. The Family contains 6 genera and 19 species which occur in all tropical subtropical and warm temperate seas.
woensdag 21 november 2012
A lot of times you see them around when you are diving Sharkpoint, Gili Trawangan or Bounty Wreck, Gili Meno. Its the Batfish. They are so common when and we see then so many times around the Gili Islands, but what do we know about them? Batfishes are recognisable on the basis of their distinctive shape, particulary juveniles, which have greatly elevated dorsal and anal fins. Other characteristics include a small, terminally located mouth, brush like jaw teeth (often with tricuspid lips), a continuous dorsal fin with 5-9 spines and 19-40 soft rays, anal fin with 3 spines and 17-29 rays, and typically a silvery adult colour pattern often with dark bars on the head and body. Members of the genus Platax are extremely tame and curious, often approaching divers at close range. Young fish are found close to the bottom, often around boat moorings, docks, jetties, and floating objects. Adults may form midwater feeding aggregation, frequently adjacent to steep outer reef slopes. The diet consists largely of benthic invertibrates and zooplankton. In their natural habitat the young of P. orbicularis mimic dead leaves, and those of P. pinnatus mimic toxic polyclad flatworms that are nearly identical in colour and shape.
dinsdag 20 november 2012
Diving around the Gili Islands gives you the oppurtunity to see unusual fish, like the Razor fish. You will find the in the harbor of Gili Air, in the front of Oceans 5 dive resort. These are small, unusually shaped fish that are related to pipefish and seahorses. They are characterised by an extremely thin or flattenend and nearly transparent body, which is encased in an integument of thin, sutured plates. The unusual appearance is further enhanced by their peculiar vertical orientation with the snout pointing downwards. However they are capable of rapid bursts of horizontal swimming when chased by a diver or preditor. Razor fish often occur in large synchronised groups, sometimes containing more than 50 individuals. The family is restricted to the tropical Indo Pacific region and contains two genera and four species, 3 of which occur in the East Indian region. The fish's diet consists of a variety of zoo-plankton and minute crustaceans. When in captivity, it is fed bait shrimp and a variety of small, live marine food. It swallows its food whole. This fish, like its closest relative, the seahorse, is toothless. As a young fish, it is prey to many larger fish. As an adult, however, the fish is thought to have little, if any, predators. This is thought to be because of its great camouflage and its "armor". The life span of the fish, unlike the reproduction method, is unknown. Maximium size to about 14 cm. Pale yellowish brown on the back and white on lower half with dark brown to black stripe from snout, through eye, to base of caudal fin. Sometimes seeks refuge among sea urchin spines.
vrijdag 16 november 2012
Sea snakes are venomous reptiles that live most or all of their lives in the sea. They're so adapted to life in the ocean that few species can crawl on land. They swim like eels with their paddle-like tail and laterally compressed body. Like marine mammals, they lack gills and must come to the surface to breathe. Sea-snakes are cold-blooded reptiles, so they live mostly in warm tropical waters, like the Gili Islands. During the diving around the Gilis you will meet some Sea snakes. Sea snakes are fully adapted to breathe, feed, breed and grow in the sea. For air-breathing animals, sea-snakes are remarkable divers. Some species can dive to 100 metres or more, and remain submerged for up to 80 minutes. This may be partly due to the remarkable ability of some species to absorb part of the oxygen they need through their skins. Their nostrils have valves that close when they are under the water. Sea snakes inject venom with their bites to subdue and kill prey, which is then grabbed in the jaws and swallowed whole. As with other snakes, the skullbones of sea-snakes are loosely attached and they can dislocate their lower jaws and slide them sideways to allowing them to swallow very large prey. Sea-snakes tend to be fussy eaters. Some only eat catfish, another only eats the eggs of two families of fish. Others dine on eels, fish, prawns, crabs and worms. Sea snake venom is among the most venomous of all snakes, yet sea snakes rarely inject enough venom to significantly harm a person. In fact, very few human deaths from sea snakes have been reported. They prey mainly on fish and other sea creatures. Sea snake venom has properties that may one day help in surgeries. Scientists are currently researching whether sea snake venom can be used as an anesthetic. Female sea snakes sometimes attract attention from more than one suitor and mate in the open water. They give birth to live young at sea. The mother then leaves the young to fend for themselves. No species of sea snakes are listed as threatened, although the distribution and status of most species is not very well known.
donderdag 8 november 2012
Sharkpoint, West Gili Trawangan, Indonesia is one of the most exciting divesites around the Gili Islands. It takes 30 minutes by boat from Oceans 5 dive resort to get there. The main attraction are the White Tip Reef Sharks. You will find them between the 20 and 30 meters in the sandy patches between the reefs, mostly sleeping. Description and Behavior Whitetip reef sharks, Trianodon obesus, are a slender species with a short, blunt snout. They are brown-gray on their dorsal (top) sides, white on their ventral (lower) sides. They have scattered dark gray spots along the sides of their bodies. The tips of their first dorsal fin and upper caudal (tail) fin lobe are brilliant white. The tip of their second dorsal fin and lower caudal fin lobe are also white in some animals. Spiracles usually present, teeth are tricuspidate (three-pronged, with a smaller secondary cusp on either side of the central blade) numbering 47-50 upper/44-46 lower jaw, in at least 2 functional rows. This species is reported to grow to 2.3 meters in length but adults over 1.6 meters long are rarely seen. Maximum published weight is 18 kg and the maximum reported age is 25 years. World Range and Habitat Whitetip reef sharks are found in tropical marine waters, are most abundant on the fore-reef, and during daylight hours are often associated with coral reefs or lying on the bottom in caves and under ledges. Individuals often return to favored resting sites at the same times each day, often for several years. Highly social, these sharks often lie together in groups on the bottom, stretched out side-by-side and even stacked like chord wood. Home ranges of individuals are very small, typically only 0.5 km² or so. In Australia they are recorded from northwestern Australia, around the tropical north and south to the Queensland coast. They are one of the most abundant species found near coral reefs, together with blacktip reef sharks, Carcharhinus melanopterus, and gray reef sharks, C. amblyrhynchos. They prefer shallow water, but have been found down to 330 m. These sharks live near the bottom or in caves and crevices. Compared to typical reef sharks (requiem sharks), this species swims in a more undulating manner. They are primarily nocturnal, but seem to be correlated with tidal ranges. They can be found in the same area for months (a few square kilometers) but territoriality is not known. They are sluggish inhabitants of lagoons and seaward reefs where they are often found resting in caves or under coral ledges during the day, or usually on a sand patch, or in a channel. They are more active at night or during slack tide in areas of strong currents. They are known to travel distances from about 0.3-3 km in periods up to about 1 year. Feeding Behavior (Ecology) Whitetip reef sharks feed nocturnally on benthic animals such as fishes, octopuses, spiny lobsters, and crabs. They have been observed feeding cooperatively at night at Cocos Island, Costa Rica, moving over the reef face like a phalanx of soldiers, flushing out sleeping prey. Foraging individuals often pause to wriggle their elongate bodies into crevices and under coral heads, twisting and turning violently and often breaking off coral and tearing their fins and skin. As such, the whitetip reef shark occupies a niche more like that of a moray eel than a typical shark. Life History One to five 60 cm young per litter. Mode: dioecism. Fertilization: internal (oviduct). Reproductive guild: internal live bearers. Description of life cycle and mating behavior: Viviparous, with 1-5 young per litter. Gestation is about 12 months. Size at birth 52-60 cm total length. Distinct pairing with embrace. One to 11 males follow a female until one gently nips her gill region; if she accepts him, he grasps one of her pectoral fins in his mouth and mates with her, their heads close together on the bottom and their bodies entwined and extending up into the water column at an angle of about 45 degrees. Mating typically lasts 1.5 to 3 minutes. They reach sexual maturity at an age of about 8 years and a length of about 1 m (males and females). Size at birth 52-60 cm total length. Conservation Status and Comments Check the Conservation Status of Whitetip Reef Sharks Note: if there are no entries found, it only means that this species has not yet been evaluated. The whitetip reef shark is a curious species that often approaches divers. It is not considered dangerous to humans. Its restricted habitat, depth range, small litter size and moderately late age at maturity suggest that, with increasing fishing pressure, this species may become threatened . Rarely reported to attack humans, but is potentially dangerous, particularly when when fish have been speared. Probably fished wherever it occurs (no data). Meat and liver utilized fresh for human consumption. The liver of this shark has been reported as toxic.
zaterdag 3 november 2012
The moray eel is a large species of eel found in warm and temperate waters all around the world. They are also around the Gili Islands. Despite their snake-like appearance, moray eels (along with other eel species) are in fact fish and not reptiles. Moray eels are found in both deep and shallow waters in tropical and sub-tropical regions. Although moray eels can be find in cooler waters occasionally, they tend to remain in the crevices deep in the ocean rather than venturing into shore. The largest populations of moray eels are found around tropical coral reefs where they are numerous different marine species found in large numbers. Specially when you are diving the dive sites around the Gili Islands named Halik, Hans and Bounty wreck you will see them. There are around 200 different species of moray eel than can range in size from just 10cm long to nearly 2 meters in length. Despite their varying size and colour all moray eels are fairly similar in appearance with an elongated body, slightly flattened towards the tail. Moray eels also have large eyes and mouths which contain large teeth. The moray eel is a relatively secretive animal, spending much of its time hiding in holes and crevices amongst the rocks and coral on the ocean floor. By spending the majority of their time hiding, moray eels are able to remain out of sight from predators and are also able to ambush any unsuspecting prey that passes. Like many other large fish, the moray eel is a carnivorous animal surviving on a diet that consists of only meat. Fish, molluscs including squid and cuttlefish and crustaceans such as crabs are the main source of food for the moray eel. The moray eel is often one of the most dominant predators within its environment but moray eels are hunting by some other animals including other large fish like grouper and barracuda, sharks and humans. Moray eels tend to mate when the water is warmest towards the end of the summer. Moray eel fertilisation is oviparous, meaning that eggs and sperm are fertilised outside of the womb, in the surrounding water, which is known as spawning. More than 10,000 eggs can be released at a time, which develop into larvae and become part of the plankton. It can take up to year for the moray eel larvae to have grown big enough to swim down to the ocean floor to join the community below
donderdag 1 november 2012
Today day 2 starts of the Padi instructor examination (IE) starts at Gili Air. Today it is only the confined water presentations. Oceans 5 candidates are making themselves ready for the final presentation. In a few hours we know more about the candidates. Hopefully we can tell you they all passed! For more information to become an instructor: http://www.indonesia-idc.com