Khao Lak Information
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The Similan and Surin National Parks are closed between May 1st and October 31st of each year. There are services, no safety measures or rescue services during that time. Wicked Diving respects the laws under which we operate and do not operaste Liveaboards during this period. If you would like to join us during this time of year – we also operate in the Komodo National Park, Indonesia…just a short hop from Bali. We can help organize flights and hotels if you need assistance.
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We are fortunate enough to encounter many different sharks on our dive sites. But don’t worry – they are all harmless! It is very common misconception about the risk sharks are to humans – and particularly to divers.
One of the most common sharks we encounter in bothe the Komodo National Park and at the Similans is the the Whitetip Reef Shark. In Thailand – we find these at several of our sites, but they seem to be most frequent visitors at the deep drop offs of Christmas Point and North Point. From our Komodo Dive center, we find them in several places, almost always on the deeper sites.
We are fortunate enough to encounter many different sharks on our dive sites. But don’t worry – they are all harmless! It is very common misconception about the risk sharks are to humans – and particularly to divers.
One of the most common sharks we encounter in both the Komodo National Park and at the Similans is the the Whitetip Reef Shark. In Thailand – we find these at several of our sites, but they seem to be most frequent visitors at the deep drop offs of Christmas Point and North Point. From our Komodo Dive center, we find them in several places, almost always on the deeper sites.
Whitetip Reef Sharks are among the most interesting animals on the reef. They are common at the Similans and in the Komodo National Park. Its scientific name is Triaenodon obesus, but it’s anything but obese! While they have the same general fearsome shape as their Great White cousins, Whitetip Reef Sharks are rarely over five feet long and usually much shorter – nothing to fear at all! They are rarely aggressive toward humans.
Whitetip Reef Sharks coexist with two other very similar sharks, the Blacktip Reef shark and the Grey Reef Shark. While all three species range from the shores of Madagascar to the reefs of Hawaii (and on to South America for the Whitetip reef shark), they generally do not migrate. All three species occupy different niches in the reef across their range. Black tips and greys are “crepuscular” – meaning they are most active at dawn and dusk, while Whitetips are most active at night.
Each species also has slightly different habitat preferences. Whitetips prefer depths of roughly 10-30 meters and the clear waters of the reef front. Blacktips occur near shore, often in lagoons, at depths of less than 15 meters. Grey Reef Sharks inhabit depths below 20 meters in both forereef and backreef environments.
Daytime hours find Whitetips resting in deeper water. Their resting habits differ in different parts of their range. In Hawaii, they commonly rest in lava tubes, while in Costa Rica, they often lie on unprotected sandy bottoms, totally exposed. They tend to rest in groups, often snuggled together, and sometimes in self-made stacks. Scientists have speculated that their communal resting may help other small fish (including wrasses and goby) keep them clean. If so, the selection of resting location in different regions may have to do with what types of species perform cleaning.
Interestingly, Whitetip Reef Sharks are the only sharks in their group that can lie still on the bottom, because they are able to pump water past their gills. Other sharks without this ability suffocate when they stop swimming.
Nighttime is hunting time for the Whitetip Reef Shark. They prowl the reef, entering holes to take prey that larger sharks can’t reach, snatching fish that retreat into fortresses to rest at night. They’re anything but graceful when attacking prey. They attack violently, often scraping and tearing their skin on the sharp rocks of the reef.
Although they’re skilled at snatching prey from tight spaces, they’re poor at getting prey in open waters. They may, however, congregate at reef drop-offs, awaiting unsuspecting creatures floating up from below. They also occasionally try to hustle catches from seals. Unlike most sharks, Whitetip Reef Sharks rarely get stirred into a feeding frenzy. They hunt in groups, but it’s every shark for him or herself!
Like most animals, Whitetip Reef Sharks fear several predators. Most are their own shark brethren, especially Tiger Sharks, although a few other species are known to attack them. The relative abundance of predator species may also determine their resting habits.
Whitetip Reef Sharks are among the most interesting animals on the reef. And because they don’t attack humans, they’re one of the easiest sharks for humans to observe.
Grey Reef Shark
Seen at the deeper sites, the Grey Reef Shark is found on the Similan Islands in small but noticeable numbers. Most frequent at Christmas point and Deep six, They are still found at a great many dive sites. Rarely seen while snorkeling….
From our Komodo Diving center we see them at several sites. This includes Crystal bommie and more. They are not infrequent, but sometimes simply not noticed among the frezy of fish life we encounter. They are not hazardous to humans (unless provoked – so don’t touch them!).
Order: Carcharhiniformes
- Family: Carcharhinidae
Genus: Carcharhinus
Species: amblyrhynchos -
- Habitat
Primarily distributed in shallow tropical and subtropical waters, the grey reef shark is often found near coral atolls and lagoons adjacent to reef habitats. It is often observed swimming along the outer edges of coral reefs. Its depth ranges from 0-920 feet (0-280 m). However, this species has been observed in waters down to 3,280 feet (1,000 m). Although more active during the night, grey reef sharks sometimes form schools during the day. These schools swim close to the bottom, over flat habitats. Grey reef sharks also form loose aggregations that lurk close to reef drop-offs. Lone individuals may be seen over shallow reefs either lying motionless on the bottom of the sea floor for long periods of time or swimming. Tagging studies show that sharks living near ocean reefs are nomadic and travel long distances along the reef habitat each day. Sharks residing in lagoon areas tend to return day after day to the same site.
Taxonomy
The grey reef shark was originally described as Carcharias amblyrhynchos by Bleeker in 1856. He later changed this name to the currently valid name of Carcharhinus amblyrhynchos. The genus name Carcharhinus is derived from the Greek “karcharos” meaning sharpen and “rhinos” meaning nose. Synonyms used in previous scientific literature that refer to the grey reef shark include Carcharias nesiotes Snyder 1904, Carcharhinus menisorrah Whitley 1944, Galeolamna fowleri Whitely 1944, Galeolamna turfiensis Whitely 1949, Galeolamna coongoola Whitely 1964, and Carcharhinus wheeleri Garrick 1982.
Common Names
English language common names include grey reef shark, blacktail reef shark, black-vee whaler, bronze whaler, gray reef shark, gray shark, gray whaler shark, longnose blacktail shark, shark, and whaler shark. Other common names from across the world include ‘anga (Tongan), bagea totoho (Gela), grijze rifhaai (Dutch), grys rifhaai (Afrikaans), ikan yu (Malay), jarjur (Arabic), kortneus-swartsterthaai (Afrikaans), mago (Niuean), malie-aloalo (Samoan), marracho enlutado (Portuguese), nga-man-nee (Burmese), pako mej (Marshallese), pating (Tagalog), qio dravu (Fijian), raira (Tahitian), requin à queue noire (French), requin bar (French), requin blanc (French), requin dagsit (French), requin gris (French), te alava (Tuvaluan), te bakoanimarawa (Kiribati), tiburón coralero rabinegro (Spanish), and tiburón de arrecifes (Spanish).
Geographical Distribution The grey reef shark is limited to the Pacific and Indian Oceans. In the Indo-Pacific, it is found in the waters off Madagascar and in the Mauritius-Seychelles region. In the western Pacific Ocean, this shark ranges from southern China to northern Australia and the Tuamoto Archipelago. It is one of the most common reef sharks in the Pacific Ocean, along with the blacktip reef shark (Carcharhinus melanopterus) and the whitetip reef shark (Triaenodon obesus). It is also found in the Indian Ocean, off the coast of India to South Africa, including the Red Sea. In this region it is often referred to as Carcharhinus wheeleri.
On our Similan Liveaboards they are most often seen in the drop-offs to deeper areas. Like Christmas Point. Christmas Point and Koh Tachai Pinnacle. While we have seen them on the flats, at the bottom of the reefs, it appears that they like more depth.
Biology· Distinctive FeaturesThis shark is medium to large in size, growing up to 8.4 feet (2.6 m) in length. It has a long, broadly rounded snout and large eyes. It does not have an interdorsal ridge running between the first and second dorsal fins. The origin of the first dorsal fin is over or just in front of the free rear tips of the pectoral fins. The first dorsal fin is semifalcate with a narrowly rounded or pointed tip. The second dorsal fin originates over the anal fin origin. The pectoral fins are large, narrow, and falcate in shape with narrowly rounded or pointed tips.
The blacktip reef shark can be distinguished from the grey reef shark by the black-tipped first dorsal fin
source: FAO Species Catalogue, Vol. 4 – Sharks of the World
· Coloration<
The grey reef shark may be confused with the blacktip reef shark (C. melanopterus). The blacktip reef shark can be distinguished by the distinct black tip on the first dorsal fin as well as black tips on the remaining fins.
· Dentition The teeth are triangular and serrated with 13-14 teeth in each jaw half. The upper teeth are narrow and serrated, semi-erect to oblique in shape with high cusps. The crown feet have coarse serrations. The lower teeth are erect or semi-oblique with narrowly serrated cusps.
·Size, Age, and Growth
Food Habits
Importance to Humans
The grey reef shark may be taken by longline shark fisheries and are valued for their fins that are used in shark fin soup. It is also utilized for human consumption and fishmeal. However, this species often occurs out of the range of most commercial shark fisheries.
These also provide a great deal of economic value to the dive and snorkeling industry. The more of them there are, the more tourism occurs. There are many “shark tours” worldwide that are entirely based on a the Shark.
Conservation
The gray reef shark, Carcharhinus amblyrhynchos, is listed as Lower Risk (LR/nt) on the IUCN Red List of Threatened Species:
LOWER RISK (LR) – A taxon is Lower Risk when it has been evaluated, does not satisfy the criteria for any of the categories Critically Endangered, Endangered or Vulnerable. Taxa included in the Lower Risk category can be separated into three subcategories:
1. Conservation Dependent (cd). Taxa which are the focus of a continuing taxon-specific or habitat-specific conservation program targeted towards the taxon in question, the cessation of which would result in the taxon qualifying for one of the threatened categories above within a period of five years.
2. Near Threatened (nt). Taxa which do not qualify for Conservation Dependent, but which are close to qualifying for Vulnerable.
3. Least Concern (lc). Taxa which do not qualify for Conservation Dependent or Near Threatened.
The grey reef shark is vulnerable to overfishing due to its restricted habitat, small litter size, and relatively late age of maturity. These factors, along with an increase in unmanaged fishing pressure, make this shark vulnerable to threats. However, at this time there is not enough data on the grey reef shark to analyze the status of populations.
The grey reef shark is currently listed by the World Conservation Union (IUCN) as “Near Threatened”. More fisheries data is required for future assessment. The IUCN is a global union of states, governmental agencies, and non-governmental organizations in a partnership that assesses the conservation status of species.
Danger to Humans
Although it is one of the most aggressive sharks, the grey reef shark will usually only attack a person when it is threatened. Even so, it has been responsible for 7 unprovoked attacks resulting in no fatalities according to the International Shark Attack File. This shark often shows curiosity and often approaches divers. If cornered or threatened is some way, the grey reef shark will display threat behavior explicitly. It will raise its snout, depress the pectoral fins, and arch its back while swimming with an exaggerated sway. If the threat continues, the shark will move with lightening speed, delivering quite bites prior to retreating. Although the bites are often serious, they are rarely fatal. This species of shark is also more likely to attack while solitary rather than schooling perhaps due to an increased feeling of vulnerability.
These are frequently seen at Similan dive sites Christmas Point, Deep Six, Koh Tachai and occasionally at other several other sites.
Here at Wicked Diving we are very lucky to encounter Manta Rays at both our Indonesian and Thailland dive centers. We have had days where and encounter was only a few seconds as a Manta passes breifly by and we have had days with 30 or more Mantas feeding around us! these massive creatures are a compelte delight to encouter and they are so unlike anything else we see underwater.
With the wide mouth, the small eyes on the sides of their head and the ability to “fly” through the waters where we struggle so hard to swim – they have a feel of something very otherworldly. No matter how many dives one has done with a Manta, there always seems to be very strong sense of awe and heart always seem t skip a beat.
Wicked Diving is helping undertake a survey of the Manta numbers in both Thailand and Indonesia. This is partly to dtermine the actual numbers (no one knows how many Manta Rays there are!) but we also are helping with this data collection to determine the economic value of Mantas in the tourism sector. If we can show the significant impact they have on tourism, we can help establish more protection for them! We support this process through our monitoring, through our Manta Ray educational tours and through our financial support.
Please read on for a huge wealth of information on the Manta Rays life, mating and feeding.
Manta Ray Biology and FAQ’s
Recognition | A gigantic devilray with gracefully sculpted, falcate pectoral ‘wings’, paddle-like cephalic lobes projecting forward from the front of the head (actually extensions of the pectoral fins, supported by radial cartilages), and a very broad, rectangular mouth at the end of the head (a mouth type known as ‘terminal’), pebble-like teeth in the lower jaw but not the upper. |
Color | Variable, ranging from black, greyish blue, to greenish or reddish brown above (black color morph sometimes with whitish, triangular shoulder patches), and nearly black, white with various degrees of greyish blotching (the precise pattern of blotching has been used to identify individuals), to almost pure white below; one albino specimen has been reported. |
Size | Disc width at birth about 4 feet (1.2 metres); maximum disc width 22 feet (6.7 metres), possibly larger (reported to widths of up to 30 feet or 9.1 metres), maximum recorded weight 3 100 pounds (1 400 kilograms). |
Distribution | Circumtropical (around the globe, generally between 35 degrees north and south latitude), including: off southeastern South Africa, Madagascar, Mozambique, Tanzania, Kenya, and Somalia; in the Gulf of Aden, Red Sea, Arabian Sea, and the Bay of Bengal, off Burma (Myanmar), Thailand, Malaysia, Indonesia, northern Australia, New Guinea, Solomon Islands, Philippines, Kampuchia, Viet Nam, China, Korea, and southern Japan; off Guam, Palau, Yap, New Caledonia, Fiji, and Hawaii; off southern California to northern Peru, North Carolina to southern Brazil, the Azores, Senegal to Liberia. |
Habitat | Occurs most often in nearshore waters (mainly over continental and insular shelves, but occasionally over deep water), near coral and rocky reefs; swim by flapping their large pectoral fins and are usually encountered near the surface or mid-waters of lagoons or seaward reefs, particularly near surge channels; in Australian waters, Mantas sometimes migrate into temperate waters; they are capable of rapid speed and juveniles sometimes leap well clear of the water, landing with a loud slap (adults drive their bodies only partway out of the water and then fall back into the sea, sometimes performing 2 or 3 of these jumps in succession); often host to one or more discfishes (especially the White Remora, Remorina albescens) and sometimes observed in association with dolphins, seabirds, sharks, and other rays (notably the Spotted Eagle Ray, Aetobatus narinari); these rays actively seek the services of cleaner wrasses (Labroides spp.), often hanging over or swimming near “cleaning stations”, sometimes several lining up to wait their turn. |
Feeding | A gigantic filter-feeder, preying on planktonic crustaceans and small schooling bony fishes; filtering mechanism consists of transverse plates of pinkish-brown spongy tissue that bridge the gaps between successive gill bars (cartilaginous skeletal elements that support the gills); when feeding, the cephalic lobes are unfurled and spread (directing and sometimes apparently scooping plankton-bearing water into the mouth), the animal often swimming in slow somersaults (vertical loops) that are repeated over and over (this behavior may keep the rays within a patch of particularly rich feeding, and may also concentrate planktonic prey to facilitate feeding); most often encountered as solitary individuals, but members of this species often aggregate in regions offering predictably rich feeding (such as off the Kona Surf Hotel at night and off Yap, in the western Caroline Islands) — with up to 50 individuals clustered in the same general area, but not forming true schools. |
Reproduction | Ovoviviparous, with each of the pups wrapped in a thin-shell that hatches inside the mother, later to be born alive; one specimen harpooned off North Carolina expelled a pup (with one pectoral fin wrapped above its body, and the other wrapped below) in mid-trajectory when it leaped, a behavior which may represent spontaneous abortion (ejected prematurely due to capture stress) or be part of normal birthing (If so, what a dramatic way to enter the world!); litter size 1 to 2 (usually 2) pups, with birthing apparently occur in relatively shallow water, where the young remain for several years before expanding their range farther offshore; mating behavior in this species has recently (July 1997) been filmed off the Ogasawara Islands, Japan, and featured one or more males rapidly chasing a female for 20—30 minutes, after which one male nips the tip of either of the female’s pectoral fins (which severely impairs her swimming), moves to her ventral surface, and inserts one of his claspers (paired intromittant organs, developed along the inner margins of the pelvic fins) into her cloaca (vent), thereby mating belly-to-belly; the male may hold onto the (much larger) female’s pectoral fin for several minutes after removing his clasper, eventually letting her go free. |
Age & Growth | Growth of newborns is apparently very rapid, virtually doubling the disc width at birth during the first year of life; males may mature at a disc width of about 13—15 feet (4.0—4.5 metres), females at a disc width of about 16—18 feet (5.0—5.5 metres), but this needs confirmation; no data on age at maturity for either sex. |
Danger to Humans | Minimal unless attacked (especially harpooned) or otherwise startled, but the enormous size and power of this ray should invite respect. |
Utilization | Formerly hunted commercially by harpoon from small boats off eastern Australia and in the Sea of Cortez (Gulf of California), this species is now rarely hunted; places where these rays can be reliably encountered (off the Kona coast of Hawaii and off Yap, to name two of the better-known locations), have spawned substantial dive-tourism industries; seemingly inquisitive, individual Mantas sometimes approach and even solicit attention from divers, apparently enjoying the tactile stimulation provided by human contact (as well as the bubbles from scuba exhaust); in areas frequented by divers, however, Mantas often become very wary of divers and cease to approach them. When approached or grasped rapidly, some individuals roll onto their backs (perhaps to keep the offending diver in sight?), sound (dive), and swim away rapidly, righting themselves only when some distance away; another behavioral response to approach by a diver from the side is curving one pectoral fin toward its back and the other toward its belly — forming an S-shape in cross-section — tilting its dorsal (top) surface toward the diver (possibly a defensive response?); in areas where divers often touch Mantas, the rays often develop pinkish skin lesions that may persist for months (apparently these lesions occur where human touch has removed the protective mucus that coats the rays’ skin). When diving or snorkeling with these magnificent, supremely graceful rays, resist the temptation to touch them and avoid obstructing their looping glide path while they feed. |
Remarks | The Manta Ray is one of the very largest and least-known elasmobranchs; although stingless, Manta Rays are actually very closely related to stingrays (family Dasyatidae), the Manta Ray, together with 9 species of devil rays (genus Mobula) comprising a subfamily (Myliobatinae) within that group; until recently, a number of Manta species were considered valid (Manta alfredi, M. ehrenbergi, M. hamiltoni), but all are now tentatively regarded as a single, world-wide species; this matter is currently under investigation by comparison of genetic samples from several populations, which should (hopefully) settle the matter once and for all. |
FAQ
Where are Manta Rays found?
Mantas are found world-wide in tropical to warm temperate seas.
Does the Manta Ray have any teeth?
Yes, Mantas have about 300 rows of tiny, peg-like teeth, each about the size of the head of a pin. The crown of each tooth has a blunt surface with three weak ridges. These teeth are often indistinguishable from the denticles (scales) inside the mouth and are not used for feeding. They may play a role in Manta courtship and mating (see below).
How do Manta Rays reproduce?
Like sharks and other rays, Mantas are fertilized internally. Male Mantas have a pair of penis-like organs — called claspers — developed along the inner part of their pelvic fins. Each clasper has a groove through which sperm is transferred to a female Manta’s body, where fertilization takes place. During courtship, one or more male Mantas chase a female for prolonged periods. Eventually a successful male grasps the tip of one of her pectoral wings between his teeth and presses his belly against hers. Then, the male flexes one of his claspers and inserts it into her vent. Copulation lasts about 90 seconds. The fertilized eggs develop inside a mother Manta’s body for a lengthy but unknown period that may be 9 to 12 months or more. One to two pups are born per litter, but no one knows where or when Mantas give birth. There is one report from North Carolina of a baby Manta being born as its mother was in mid-leap after being harpooned, but this may not be typical. Mother Mantas may take a year off between pregnancies to re-build her energy stores.
How big is a newborn Manta Ray and where have they been found?
Based on the smallest free-swimming members of this species, newborn Mantas are about four feet (1.2 metres) across. Very few newborn Mantas have been reported and we know almost nothing about where they are born.
Ed. Note: Recently there was a birth of a Manta at an Okinawa aquarium. This link might be broken, but please google/you tube for Manta Ray birth”
http://www.youtube.com/watch?v=OIc_px_9xBE
What is the size of the largest Manta Ray ever found?
Records of giant Mantas are notoriously difficult to verify. The largest reported in the scientific literature measured 22 feet (6.7 metres) across and there is one report of an individual 30 feet (9.1 metres) across. But most Mantas encountered by people are about 12 feet (4 metres) across.
How long do Manta Rays live?
No one knows how long Mantas live. Based on known lifespans of closely related (but much smaller) warm-water rays, Mantas may live up to 25 years or so.
Why do Manta Rays have different color patterns?
Mantas vary enormously in color pattern on the shoulders and, especially, the undersurface of the body. It is not known what functions — if any — these differences hold for Mantas, but they are very useful for researchers in distinguishing one individual from another. The shape and extent of the shoulder patches, the precise pattern of spots and blotches on the undersurface, and the lifetime pattern of scars form a pattern of markings as unique as a human fingerprint. Manta markings can be photographed and filed in an organized way to allow cataloguing all individual Mantas in a given area. There are also intriguing regional differences in Manta color patterns. For example, specimens from the eastern Pacific often feature dusky to mostly black undersurfaces, while those from the western Pacific are typically snow white underneath.
Have Manta Rays ever killed anyone?
There are numerous reports, mostly anecdotal, of harpooned Mantas leaping on small vessels and smashing them or their occupants. Some of these cases may have resulted in the death of one or more people due to crushing or drowning, but it must be borne in mind that the animal was simply trying to defend itself. Divers have sometimes been injured accidentally while trying to ride or photograph Mantas from too close. But there is no record of an unprovoked Manta attacking or injuring a person.
What preys on Manta Rays?
Only large warm-water sharks, such as the Tiger Shark (Galeocerdo cuvier), are known to prey upon Mantas.
ED note – recent sightings of Killer Whales in the area provoked an unusual finding – They prey on Manta Rays!
Is it ok to ride Manta Rays?
No wild animal is benefited by being ridden, and Mantas are no exception. Riding a Manta increases its swimming effort — using up calories that might have been better used growing, reproducing, escaping predators, or healing wounds — and may stress the animal unduly. While riding Mantas, people have scraped their skin, gone too deep, risen too fast, or fallen off and been injured accidentally. Simply touching a Manta may remove some of the mucus coating that protects the animal from marine infections. Last, but not least, some Mantas clearly do not like being touched and may speed away, ending the encounter by sheer distance. For all these reasons, touching or riding Mantas is to be avoided.
Why are Manta Rays bodies flattened?
Mantas bodies are flattened from top-to-bottom because their ancestors were, too. Mantas are derived from stingrays, which are flattened bottom-dwellers that swim by undulating their expanded pectoral fins. This flattened body form is advantageous for hiding in the bottom sediment, making it difficult for predators to see partially buried stingrays. During the course of their evolution, Mantas lost the stinging barb and their pectoral fins developed into graceful, flapping wings, but their flattened body shape remained.
Do Manta Rays migrate?
Given the scattered nature of their planktonic food, it is very likely that Mantas migrate. But little is known about where they travel and when. Each autumn (March-April) at Ningaloo Reef, of the coast of Western Australia, Mantas appear in large numbers, apparently to take advantage of the rich feeding afforded by the mass spawning or corals and other reef creatures that takes place at this time. Where the Mantas go when they leave Ningaloo is not known. Manta movement patterns are presently being studied by tagging and sonic telemetry at numerous locations, including Ningaloo Reef, the Ogasawara (Bonin) Islands, Hawaii, and the Sea of Cortez.
Do Manta Rays sleep?
No one knows. In vertebrates (backboned animals), sleep is characterized by a profound change in brainwaves. This has never been demonstrated experimentally in Mantas or any other elasmobranch (shark or ray). Actively swimming sharks and rays, such as the Manta, are believed to swim constantly, never stopping from birth to death. Although it is feasible that some parts of the brain shut-down while the parts of the brain responsible for coordinating swimming movements stays awake, this has not been demonstrated experimentally.
Are Manta Rays social?
Apart from courtship and mating (which is quite elaborate, see above), Mantas do not appear to be particularly social. Mantas frequently aggregate at rich feeding sites and cleaning stations, but there is little evidence of social interaction among them. Actively predaceous animals — such as lions, wolves, sharks, and dolphins — often establish social hierarchies (structures) and signals. Outside breeding season, most passively grazing animals — such as cows, deer, antelopes, and apparently Mantas — show little awareness in one another other than avoiding collisions.
Are Manta Rays more active by day or by night?
Mantas are most commonly seen during daylight hours because that’s when most observers are most active. We have virtually no idea what Mantas do at night or how active they are. Manta courtship (see above) seems to feature prolonged chasing, which would be best accomplished in clear, open water during the day. Mantas may feed most actively at night, when many planktonic creatures rise surfaceward, providing a rich bounty on which Mantas may feed. Beginning about an hour after dark at a certain seaside hotel on the Kona Coast of Hawaii, groups of Mantas are often observed feeding on krill and other planktonic organisms concentrated in the hotel’s underwater lights. Unfortunately, this spectacle has largely ceased, possibly due to too much interaction from the throngs of excited divers and snorkellers who converged on the feeding Mantas.
How deep do Manta Rays swim?
Divers have observed Mantas as deep as 100 feet (30 metres), but no one knows how deep they can swim.
What is the difference between mantas and mobulas?
Mantas and mobulas (also known as “devil rays”, of which there are 9 species) are similar in form, sharing paddle-shaped cephalic lobes and gracefully curved pectoral wings. Mantas grow much larger than mobulas. Mantas reach widths of at least 22 feet (6.7 metres), while most mobulas are 3 to 10 feet (1 to 3 metres) across. Mantas and mobulas are most readily distinguished by the position of the mouth: in Mantas, the mouth is terminal (located at the front of the head), while in mobulas the mouth is subterminal (located underneath the head, as in many sharks).
Is it true Manta Rays have rescued fishermen?
Probably not. If (apart from breeding season) Mantas are not terribly interested in one another, they’re probably not interested in hapless fishermen, either.
What are cephalic lobes and what is their function?
The forward-pointing, paddle-like organs at each corner of a Manta’s mouth are termed “cephalic lobes”. They are basically forward extensions of the pectoral wings, complete with supporting radial cartilages. Mantas have been observed using their cephalic lobes like scoops to help push plankton-bearing water into their mouths. When Mantas are not actively feeding, the cephalic lobes are often furled like a flag ready for storage or held with their tips touching like the swinging doors of an Old West saloon. Either of these cephalic lobe positions may reduce drag during long-distance swimming.
Why do Manta Rays sometimes jump out of the water?
Mantas may leap completely out of the water for a variety of reasons. They may do it to escape a potential predator or to rid themselves of skin parasites. Or they may leap to communicate to others of their own species — the great, crashing splash of their re-entries can often be heard from miles (kilometres) away. It’s anyone’s guess what they may be trying to communicate. Leaping male Mantas may be demonstrating their fitness as part of a courtship display. Since these leaps are highly energetic and often repeated several times in succession, they may simply represent a form of play.
Have Manta Rays ever been exhibited in an aquarium?
Very few aquariums have the enormous tanks and filtering capacity needed to display a full-grown Manta. Although there have been many valiant attempts to display Mantas in aquaria, most specimens refuse to feed and die within a few hours or days of being deposited in a tank. The Expo Aquarium, in Okinawa, Japan, has successfully maintained Mantas for as long as 36 days. Despite the failures of the past, several large aquaria continue to refine and test capture and transport methods toward the goal of maintaining a healthy Manta in captivity indefinitely.
Are Manta Rays hunted anywhere in the world?
In the 1990’s, targeted harpoon fisheries in the Philippines and off the Pacific coast of Mexico decimated resident populations. Due to the scarcity of catches, Mantas are rarely targeted in these locations today. Mantas are sometimes ensnared in drift or set nets, particularly in tropical parts of the western Pacific and Indian oceans. These catches are rarely reported, so it is difficult to assess the threat posed to manta populations by these “incidental” captures.
Do Manta Rays have any monetary value?
Mantas are valued commercially for their tasty meat, sandpapery hide, and oil-rich liver. A Manta in captivity is worth a small fortune to any public aquarium with the facilities to display it, a reality that drives a small but recurrent harvest in Japan and possibly other areas.
The current calue for tourism is currently being assessed. It is estimated to have a tourism value in the hundreds of millions of dollars, with Manta ray dives in Hawaii, Thailand and Indonesia driving a large base of eco-tourism.
Are Manta Rays in danger of extinction?
We don’t know. Mantas seem to be fairly abundant in some areas, rare or absent in others. Until we understand the extent and dynamics of Manta stocks, there is no way to assess their conservation status. Based on their low birth rate, Mantas are probably highly vulnerable to sustained fishing pressure and habitat degradation. This likelihood would seem to favor a cautionary approach to Manta exploitation and management until such time as we have the sound scientific data to make a more informed assessment of this species’ risk of extinction.
Why are Manta Rays important?
So little is known about the basic biology and life history of Mantas, little can be said about their importance from a scientific or ecological standpoint. It can be argued that Mantas are important because they add to the beauty, diversity, and mystery of our world. Without Mantas, our planet would seem a significantly poorer place.
The Trumpetfish can be recognised by its long body, tubular snout with minute teeth, its chin barbel and the series of short dorsal spines.
The coloration of this species is variable. It is often brown or green with pale stripes and bars, and white spots posteriorly. A yellow (or xanthic) color variety is common in some areas. Individual fish have the ability to change their colors very quickly.
This species grows to 80 cm in length.
The Trumpetfish uses stealth and camouflage to prey on small fishes. It often approaches its prey vertically, darting down from above and sucking the prey into its long snout.
It is known to sometimes follow other fishes. Presumably following herbivorous fishes such as the Blue-lined Spinefoot allows the Trumpetfish to more easily approach potential prey without detection.
There is only one species in the genus Aulostomus. It occurs on coral reefs throughout the Indo-Pacific and eastern Pacific.
In Australia the Trumpetfish is recorded from most tropical waters and down the east coast to central New South Wales.
Leopard Sharks
Leopard Sharks are the common Name in Asia for Stegostoma fasciatum,which is very common on the Similan and Surin Islands.
In The Americas it is the name for a very different shark – Triakis semifasciatum.
We see Leopard Sharks on many of our dive sites. Some common sites are Koh Bon, bon Soong wreck and Koh Tachai. We also see them on many other sites, but not so frequently.
Here is a blog entry from one of our guests:
While on holiday last winter to the Similan Islands, Thailand I had the opportunity to go diving for the first time. I like, many others, had heard of the horror stories of sharks in the oceans and I would be lying if I said I was not nervous when I was told we would be going to see a species of shark called a “Leopard shark”. The name leopard shark immediately put an image of this huge sea monster in my mind but once we got to the dive site I could not have been more surprised and amazed at what fantastic creatures leopard sharks are.
When I first saw this amazing creature swimming along the ocean floor I was really amazed. The name leopard shark is very fitting due to the spots on its body. I was a bit apprehensive and expected the shark to earthier come flying at me or simply swim away. Despite all the comments that these are actually friendly creatures in the dive briefings, I was still not sure. Our Instructor, Gae, told us that if we did see one we would slowly approach from the front and spend some time with one. I have since learned that leopard sharks are not usually bothered by humans and spend much of their time laying on the sand.
As I did my dive during the day time the leopard sharks that we saw were very inactive, just laying on the bottom which makes sense, considering that they are nocturnal sharks. In many areas leopard sharks are used to divers and if you do not get too close then you can observe them really well. We were that lucky! Wicked Diving is very specific about not getting too close to any marine life…but I never believed that I would be hovering 2 meters from a shark….but I was! Most of the time leopard sharks will laze around in a sheltered area. In this case, one shark was lying right next to a large coral head off Koh Tachai. We also saw two at Koh Bon the next day.
Since diving the Similan Islands made such a great positive impact on me I became really interested in leopard sharks my local sea life center has a few there and I have been to observe them there. I have found out a great deal more information about these creatures since my dive. One of the most fascinating things is there diet as I am sure when most people hear the word shark they imagine a great white eating anything it can find in the ocean. The leopard shark has a diet that consists of things like snail’s sea snakes and small fish. It hunts at night getting into all kinds of nooks and crevices to hunt for its prey.
Something that is quite unique to leopard sharks and that is unlike many other species of shark is that it does not need to swim in order to be able to breath. I noticed this on my dive that the leopard shark was not moving and was just lying there. I asked Gae when we returned to the surface what the reason for this was and it turns out that the leopard shark can pump water over its gills. I found this really interesting and have since learned that more often than not leopard sharks will lie on the bottom of the ocean facing the current as this helps them breathe even easier.
I just want to say again what amazing creatures these are and I can not recommend taking the chance to see them in the wild. The leopard shark was a huge influence on me in getting more interested in diving and now I’m doing my rescue course and hoping to head back to Wicked Diving, Khao Lak for a Divemaster Course.
Thanks for that! We look forward to having you join the divemaster team here at Wicked!
More details in the Leopard shark
Description & Behavior
The zebra shark, Stegostoma fasicatum (Hermann, 1783), is also known as a leopard shark in SE Asia. The zebra shark has a cylindrical body with prominent ridges on the sides and 5 gill slits (slits 4 and 5 overlap). The tail lacks a ventral lobe and it is as long as the body. This shark has a broad head, small barbels, and a transverse mouth located in front of the eyes. Its spiracles are as large as its eyes. The spineless dorsal fins are back to back. The anterior dorsal fin is much larger than the posterior dorsal fin. The first dorsal fin appears above the bases of pelvic fins, the second dorsal fin is about as large as the anal fin. The body is gray-brown with dark spots in adults. Juveniles are darker with light stripes and spots. Maximum size is about 3.5 m, average size between 2.5-3 m.
World Range & Habitat
Indo-Western Pacific: South Africa to Red Sea and Pakistan, India, Sri Lanka, Bangladesh, Indonesia, Thailand, Vietnam, Philippines, China, Japan, Australia, New Caledonia, Palau. Lives over the continental and insular shelves. Very common around coral reefs, often on sandy bottoms, but little is known about its biology. It is known that this species props up its pectorals in the sand and faces the current with open mouth. Such behavior and its inactivity during the day points towards a more sluggish life style and indicates that it is probably a nocturnal hunter. Recorded to have entered freshwater.
Description & Behavior
The zebra shark, Stegostoma fasicatum (Hermann, 1783), is also known as a leopard shark in SE Asia. The zebra shark has a cylindrical body with prominent ridges on the sides and 5 gill slits (slits 4 and 5 overlap). The tail lacks a ventral lobe and it is as long as the body. This shark has a broad head, small barbels, and a transverse mouth located in front of the eyes. Its spiracles are as large as its eyes. The spineless dorsal fins are back to back. The anterior dorsal fin is much larger than the posterior dorsal fin. The first dorsal fin appears above the bases of pelvic fins, the second dorsal fin is about as large as the anal fin. The body is gray-brown with dark spots in adults. Juveniles are darker with light stripes and spots. Maximum size is about 3.5 m, average size between 2.5-3 m.
World Range & Habitat
Indo-Western Pacific: South Africa to Red Sea and Pakistan, India, Sri Lanka, Bangladesh, Indonesia, Thailand, Vietnam, Philippines, China, Japan, Australia, New Caledonia, Palau. Lives over the continental and insular shelves. Very common around coral reefs, often on sandy bottoms, but little is known about its biology. It is known that this species props up its pectorals in the sand and faces the current with open mouth. Such behavior and its inactivity during the day points towards a more sluggish life style and indicates that it is probably a nocturnal hunter. Recorded to have entered freshwater.
Endangered Species….
Read the UN report on endangered species…
The Nurse Shark is rare, but is found among the boulders of the Similan Islands. We offer a special educational tour on Sharks of the Similan Islands each year. While we do encounter Nurse sharks – these are the least common ones of this region.
Nebrius ferrugineus
The Tawny Nurse Shark’s common name is derived from its ability to suck up prey using a powerful sucking motion with its throat, just like a baby being nursed. This talent is used to vacuum out octopus, fish and crabs from the reef or it can be reversed to fire a jet of water at any captor. This also means they are no threat to humans – like Leopard Sharks, they do attack humans.
Some details on the Nurse Sharks:
A large, tropical inshore shark of the continental and insular shelves of the Indo-Pacific,often in the intertidal in water scarcely able to cover it and from the surf line down to a few metres depth, commonly at 5 to 30 m and ranging down to at least 70 m on coral reefs. It occurs on or near the bottom in lagoons, in channels, or along the outer edges of coral and rocky reefs, in areas with seagrass and sand on reefs, sandy areas near reefs and off sandy beaches. It prefers sheltered areas in crevices and caves on reefs but often occurs in more exposed areas in depressions or crevices. Young prefer crevices in shallow lagoons but adults are more wide-ranging.
The nurse shark is primarily nocturnal, resting in the daytime in shelters but prowling slowly about around reefs at night, although some individuals may be active in the day. In Madagascar it is described as day and night-active, and in captivity they get quite active and vigorous when food is presented to them during the day. They are social, gregarious sharks when at rest and form resting aggregations of two to a half-dozen or more in shelters, and are often seen piled inertly across or on top of one another. When resting, they are extremely sluggish. This shark has a limited home range, and individuals often return to the same area every day after foraging.
We do see them during the day, but generally in the resting pose (in nooks) rather than swimming or predating.
Reproduction
ovoviviparous (aplacental viviparous) with cannibal vivipary or uterine cannibalism in the form of oophagy (Inside the eggs, they eat each other!!!). This shark has been described as an oviparous or post-oviparous shark that retains the egg-cases until they hatch and the young are born, but recent evidence indicates that this is incorrect. Pregnant females collected from Okinawa have had one or two foetuses per uterus, 297 to 595 mm (the latter near term), with the yolk sac reabsorbed and a greatly expanded stomach filled with yolky material in foetuses 338 and 595 mm long, and also had cased eggs in the uterus. Apparently this species practices oophagy on relatively large, cased nutritive eggs (unlike many lamnoids which have very small nutritive eggs), and is the first orectoloboid known to have uterine cannibalism (creepy!). It is not known whether foetuses of this species eat other foetuses(adelphophagy) as with the sand tiger. The presence of two foetuses 338 and 297mmin the same uterus, with the smaller one slender and the larger bloated with yolk, suggests that competition between siblings for the relatively big eggs is likely and could even eliminate the less successful sibling. Adelphophagy is less likely although early stages need to be examined to eliminate it.
The Number of young per litter uncertain; at least four young per uterus has been suggested from cased eggs, but the size and enormous girth of the near-term Okinawan foetus and the two smaller foetuses in a litter suggests that litters are smaller, possibly one or two per uterus or even one per female, and that numbers of cased eggs in the uteri cannot be used to extrapolate litter sizes in this species. In captivity adult females lay cased eggs on the bottom, but these do not develop, and could be nutritive and unfertilized. Such free eggs may have been the basis of the suggestion that this species is oviparous.
The tawny nurse shark breeds in July and August off Madagascar. Food of this shark includes corals, crabs, lobsters and other crustaceans, Octopus, squid and probably other cephalopods, sea urchins, and reef fish including surgeonfish (Acanthuridae), queenfish (Carangidae) and rabbitfish (Siganidae), and occasionally sea snakes. While foraging the tawny shark moves along the bottom and explores depressions, holes and crevices in reefs. When it detects prey it places its small mouth very close to the victim, and uses its large pharynx as a powerful suction pump to rapidly suck in reef organisms that may be out of reach of its teeth. A few large individuals dissected had quantities of small, active reef fishes in their stomachs, presumably sucked in by the sharks as the prey fishes lay inert in shelters or on the bottom at night. Individuals caught by fishermen may reverse this sucking action, and blast streams of water out of their mouths and into the faces of their captors; they are said to make a grunting sound between blasts. It is not known if spitting water is deliberate and defensive or if the sharks are actually aiming the water at the anglers. They also tend to spin when hooked on a line, making them difficult to handle and subdue.
The shark fight back – even when on the boat! Very cool!
The nurse shark superficially resembles certain other large, partly or mostly sympatric, active reef sharks including the sand tiger shark, sicklefin lemon shark, and reef whitetip shark. Its status as a game fish in Australia, unlike the nurse shark in the western Atlantic, suggests that it may be a more active swimmer when not resting on the bottom.
Size
Size: Maximum about 314 to 320 cm, though most individuals are smaller; size at birth has been reported as about 40 cm but subsequent data from a pregnant female captured off Okinawa suggest that it may reach 60 cm or more at birth, while a 79 cm female from Navotas market in Manila, Philippines, had a somewhat bloated stomach full of yolk, suggesting that it was newborn or a term foetus; males are mature at about 250 cm and reach at least 301 cm; adult females are 230 to at least 290 cm.
The ones we see in Thailand are smaller, though mostly likely due to extenzive fishing.
Interest to fisheries…
Common or formerly common in areas where it occurs, and caught inshore by fishermen in Pakistan, India, Thailand, and Philippines, and probably widely captured elsewhere.
It is utilized fresh and dried-salted for human food, its liver is rendered for oil and vitamins, its fins are used in the oriental sharkfin trade, and offal is processed into fishmeal. Its thick, armour-like hide is potentially valuable for leather. Off Queensland, Australia, it has been fished as a big-game shark, and large individuals are prized as powerful fighters by sports anglers. Apart from anglers who target this fish, it is apparently primarily caught only as an untargeted bycatch of fisheries in inshore waters in ntes, on line gear, and in fish traps.
Conservation Status : The conservation status of this shark is uncertain and urgently needs investigation despite its wide range. In some areas, including the Gulf of Thailand where it was commonly caught in the 1960s, it may have been depleted due to increasing fisheries activity and habitat degradation. Also, reef habitats have been extensively damaged or destroyed by dynamiting and poisoning in parts of its range, including Indonesia and Philippines, which probably have had an adverse effect on this species both directly and through decimation or elimination of its prey. Its docility and inshore habitat makes it particularly susceptible to a wide variety of fishing gear, to harassment and injuries by divers, and to reef destruction and pollution.
Threat to humans: This has been described as a much more docile species than its close relative, Ginglymostoma cirratum, and apparently tolerates close proximity of divers and usually allows humans to touch and play with it without biting. PLEASE DON”T TOUCH ANY SPECIES OF MARINE LIFE! However, there are a few records of these sharks biting their tormentors, and clamping tightly onto them. Because of its size, strength, powerful jaws and small but sharp cutting teeth, the tawny shark should be treated with the respect due it. It is a favorite species for observation by divers within its enormous range, and dive sites where it is viewed are known from Thailand (Andaman Sea) and the Solomon Islands.
Longfin bannerfish, also known as Black and White Heniochus, are a beautiful species of marine fish that live in the waters of the Indian Ocean. They flaunt a long, elegant dorsal fin, thick black and white bands, and just a touch of striking yellow coloring on the tail fin. As exotic as their fins are lengthy, these fish delight divers and snorkeling visitors alike.
Often confused with two other species of tropical fish, there are a handful or discreet differences between the three. A seasoned diver will tell you that the longfin bannerfish does not boast the same long snout that its look-alike, the Moorish idol, does. However, the longfin bannerfish’s snout is more pronounced than that of its other look-alike, the schooling bannerfish.
Other small differences – like a more rounded anal fin, smaller chest, and a very slight difference in the length of a black band – separate the two. In fact, if you are not specifically looking for the dissimilarities, you would never be able to determine which species is which. Because the longfin bannerfish and Moorish idol are so strikingly similar, the longfin bannerfish is often called “The Poor Man’s Moorish Idol.”
Now that you know exactly what divides the longfin bannerfish from the Moorish idol and the schooling bannerfish, you can put your knowledge to the test the next time you go snorkeling or diving in the Andaman sea. At a decent size of just under 10 inches, you should be able to distinguish the inconspicuous dissimilarities of the longfin bannerfish – if, that is, he will grant you an audience of more than just a few moments.
For an up close and personal encounter with these fish – why not join our Similan Liveaboards – or even a Surin Snorkeling tour?. You might also chance a meeting if you dive between Southern Japan and Lord Howe Island in the Pacific. Then delve into the crisp waters – longfin bannerfish thrive in temps between 72 and 78 degrees Fahrenheit – but we still have them in Thailand with higher average water temps. This fish provides a good range of territory to explore as it lives in depths of 7 to 246 feet.
As you snorkel, prepare for the striking contrast of the longfin’s black, white, and yellow scales against the ocean’s blue waters. The graceful longfin bannerfish will make the global trip worth the effort, and might even convince you to add some of the creatures to an aquarium of your own.