Maximum Width: 16 feet (5 m) 


Lifespan: Unknown (over 27 years)

Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Chondrichthyes (cartilaginous fish)
Subclass: Elasmobranchii (sharks, skates and rays)
Superorder: Batoidea (skates and rays)
Order: Myliobatiformes (rays)
Family: Mobulidae (devil rays – cephalic fins)
Subfamily: Myliobatidae (2 manta and 9 devil ray species)
Genus: Manta
Species:alfredi

Description

Manta rays are the largest rays in the Mobulidae family and until recently, the genus was thought to consist of just a single species, Manta birostris. Recent evidence based on morphology and meristic data has confirmed at least a second species in the genus, Manta alfredi [1]. M. birostris or “oceanic mantas” can be differentiated from M. alfredi visually in the field by their  much larger size, their coloration, and the presence of a caudal spine. At the base of the tail just below the dorsal fin, oceanic mantas have retained a calcified mass that contains a small, embedded spine, essentially a vestige of their ancestry. Their disc width (DW: measured from wing tip to wing tip) can span 6.7 m [2] with one specimen reportedly as large as 9.1 m [3]. M. alfredi, or “resident manta rays” do not possess this calcified mass. When differentiating dead specimens, differences in the appearance of the skin and denticle morphology, as well as the number of teeth present on the lower jaw can also be used to identify species. On the bottom jaw exists 12-16 rows of small cusped teeth in oceanic mantas, and 6-8 rows in resident mantas, with no teeth existing in the upper jaw for either species. These very small teeth barely penetrate the skin covering and are another vestige of an evolutionary era when their ancestors used their teeth to feed.

Most rays are bottom feeders, with their mouth located on their ventral side, and a pair of spiracles on the top of their head, from which they take in water and pump it pass their gills to breathe. Mantas are unique in that their mouth is located at the front of the head projecting forward rather than downward, and evolutionary adaptation to take advantage of the large abundance of zooplankton. The spiracles in manta rays, although still present, are no longer used. Instead, water enters their mouth while they swim, passes over the gills, and provides oxygen to the blood. A manta ray’s internal gill arches can be seen, when the mouth is wide open.

Theword ‘Manta’ is Spanish for cloak, referring to their large, blanket shapedbodies. In Hawaiian, they are called hāhalua.The most common resident manta morph has a black dorsal cape with white shoulder patches and a white chevron that stretches anteriorly from the insertion point of the dorsal fin [1]. The ventral side is typically cream to white in color with variable dark markings that can occupy the entire ventral surface but most are concentrated towards the center of the disc. Each manta ray has aventral spotpattern that is unique. These patterns are visible at birth [4], and appear to remain unchanged over the life ofthe individual [5-7]. These unique patterns allow researchers to discriminate and track individuals over time (see manta research). A melanistic morph exists that is almost completely black on both the dorsal and ventral surfaces except for a white blazealong the mid-line that is variable in size.  The much less common leucistic “white manta” morph has an almost entirely white dorsal surface and a ventral surface that is much lighter in overall coloration. Less than 20 of these have been observed worldwide [1]. The tremendously large body size of manta rays has likely been beneficial in reducing predation pressure. With less predation pressure, the benefits ofcounter-shading become less important,possibly allowing morph variants to proliferate successfully [8].

The wingspan of resident manta rays can reach about 16 feet (5 meters) but will vary geographically [9]. They are 2.2 -2.3 times wider than they are long [2, 9]. Ray pectoral fins have evolved into large triangular wings. These wings are used by the manta ray to propel through the water. Their skin is covered with dermal denticals (small tooth-like structures) just like their shark cousins. A mucus coating covers their skin, creating an important defense against infection. Their long and narrow tail lacks a spine or a stinger, is slightly flattened, and shorter than the width of the animal. A small dorsal fin is located at the base of the tail. The eyes are located laterally just behind their cephalic fins, giving them the ability to see forward and downward very easily. Their ability to see upward and behind their body, however, is poor. The oil content in their liver is high, providing them with buoyancy since they do not have a swim bladder.

Although most elasmobranchs have relatively small brains, both devil rays and galeomorph sharks independently evolved large telencephalons and cerebellums, characterized by high brain:body ratios [10]. What function the enlarged telencephalon and cerebellum areas play or why they evolved together remains unclear [11]. Manta rays possess a rete system, a network of blood vessels that surround their braincase, presumed to keep this organ warmer than the surrounding tissue [12]. Some sharks also possess rete systems.

As manta rays move throughout their aquatic environment, they process information through many different sensory channels allowing for a complex repertoire of signals and behaviors to be used for finding food, mates, escaping predators, and to facilitate social interactions with conspecifics. These sophisticated senses incorporate: 1) an olfactory and gustatory system, 2) a visual system, 3) a mechanosensory system, which includes hearing and touch, and 4) an electrosensory system [13].

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Range and Habitat

Resident mantas are more likely to be observed in shallow coastal areas around rocky and coral reef habitats where productive upwellings exist, commonly sighted inshore, within a few kilometers of land. They have been observed as far north as the Yaeyama Islands, Japan, Hawaii, the Canary Islands, the Red Sea, Sri Lanka, and Thailand, and as far south as the Solitary Islands, Australia, French Polynesia, Senegal, Durban, South Africa, the Maldives, and Perth, Australia. No sightings exist for the eastern Pacific and except for two a off the coast of Senegal from northwest Africa, sightings for the eastern Atlantic are extremely rare [14]. In general, they can be found in tropical and subtropical regions of the Pacific, Atlantic, and Indian oceans within 30 degrees of latitude to the north and south of the equator [1].

Long term sighting records at established aggregation sites suggest that M. alfredi may be resident to these areas and may exhibit smaller home ranges [5, 15-17]. Areas of high productivity could eliminate the need for manta rays to migrate to other areas [6] by providing sufficient food resources year-round. Thus far, no evidence of inter-island migration exists from a known manta ray population in Kona, Hawaii [6].

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Behavior

Congregations occur around rich food sources or at specific locations on the reef known as cleaning stations [18], where individuals solicit host cleaner fish to remove parasitic copepods from their body’s surface. When more than one host cleaner fish species shares in the cleaning behavior, each may focus on a different region of the manta’s body in order to reduce interspecific competition [17].

Although Mobula species are reported to be free from parasites, Mantas can have parts of their bodies thickly covered with several species of parasitic crustaceans [19]. In Japan, the parasitic copepods are thought to belong to the Pandaridae family [5]. For clients, the main benefits to being cleaned are likely a reduction in ectoparasite load but this has been difficult to measure due to the methodological problems in quantifying ectoparasite intensity [20].

Host cleaner fish vary by region. In Yaeyama Island, Japan, the cleaner wrasse (Labroides dimidiatus) and other small shrimps commonly do most of the cleaning [5]. In Hawaii, predominantly Hawaiian cleaner wrasses (Labroides phthirophagus) and saddle wrasses (Thalassoma duperrey) are observed removing parasitic copepods from the surface of the manta ray’s body (M. Deakos, pers. Obs.). T. duperrey will concentrate mostly on the external body surface, whereas L. phtyirogphagus will concentrate mainly inside the mouth and around the gill slits. In Mozambique, various butterfly fish (family Chaetodontidae) specialize in bite wounds while Seargant Major fish (Abudefduf saxatilis) concentrate more around the mouth region [17, 21].

Strong site fidelity occurring at specific feeding and cleaning stations [5] has created popular tourist attractions where visitors pay to swim or scuba dive with the manta rays [6, 15]. Aggregations around cleaning stations are commonly used as reliable areas for guided swim-with manta tours. Some well known resident manta ray aggregation areas worldwide that have become popular tourist destination areas include Komodo Marine Park, Indonesia [15], Yap, Micronesia [5], Palau, Yaeyama, Okinawa, Japan [22], Kona , Hawaii  [6], Bora Bora, French Polynesia [23], Mozambique [17], the Republic of Maldives [24, 25], and Ningaloo Western Australia [26, 27]. In the Republic of Maldives, divers are taken to watch manta rays at the same diving spot each time demonstrating daily site fidelity is strong. In some locations, these cleaning stations are active year-round, while in others the presence of manta rays at inshore reefs is seasonal or erratic [15].

Mantas are occasionally observed leaping partially or completely out of the water; sometimes one after the other. The purpose of this behavior is unclear [5] but some have suggested that it may be related to mating displays, giving birth, or an attempt to get rid of parasites or remoras (Remorina albescens) attached to the surface of the manta ray [28]. One oceanic manta was observed with seven large remoras attached to it’s body [19]. Mantas have been observed trying to remove remoras by rubbing against rocks or the sandy bottom [5]. The splash created when reentering the water during a breach can be audible for some distance away if the seas are calm [2] and therefore may be used as an acoustic form of communication.

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Reproduction

Manta rays are oviparous, giving birth to a live young that hatches from an egg, carried inside the mother. After hatching from the egg case that is attached to the female’s oviduct, the pup continues to feed on the mother’s uterine milk until fully developed. The pup is born live as a miniature version of the adult.

In free-ranging manta rays some speculate that they may give birth in relatively shallow water where the pups remain for several years before expanding their range [29]. The only reported birth was for a resident manta female in captivity at the Okinawa Expo Aquarium following what was determined to be a 12 -13 month gestation period [30]. The newborn was abandoned immediately after birth and the mother was seen mating again within hours.
Pregancy rates for resident mantas have been estimated using long term sighting records of females observed pregnant every 2-3 years on average, with some females becoming pregnant in consecutive years [5, 25, 31]. Although giving birth to a single pup at a time appears to be the norm for both species based on disections of pregnant females [2, 19, 32-34], two pups may be conceived on occasion [31].

The sex of a manta ray can be determined by the presence of claspers in males, and their absence in females. Sexual maturity in a female can sometimes be determined if they have visible mating scars (spot scarring and abrasions usually on the dorsal or ventral side of the left wing tip) or if they are obviously pregnant [31]. A pregnant female close to term is exceptionally rotund and unmistakable. Among males, calcification of the claspers occurs rapidly over a relatively narrow range of growth [35] and the majority of calcification occurs once the claspers have extended beyond the length of the pelvic fins [31]. Since the onset of clasper calcification in many shark species coincides with a rapid rate of clasper growth and gonadal maturation [e.g., 36] claspers extended beyond the pelvic fins were used as a reliable indicator of sexual maturity in male manta rays. 

The first detailed description of a manta ray mating sequence was for oceanic mantas observed off Ogasawara Island, Japan [37]. The sequence of events involved: (1) a male following directly behind a female for 20-30 minutes making several attempts to bite her pectoral fin as she traveled at a speed of 10 km/hr; (2) the male succeeds in biting the female’s pectoral fin positions his ventral side against hers; (3) the male inserts his clasper into the female’s cloaca for 60 – 90 seconds; (4) the male remove’s his clasper and continues to hold her pectoral fin in his mouth for several minutes; and (5) the male releases the female’s pectoral fin and both individuals swim apart. This mating sequence was observed in 10-20 m water depth over rocky reefs and 100-200 m from the beach. Similar mating train behavior has been described for resident mantas off Yaeyama Island, Japan, [5], and at North Male Atoll in the Republic of the Maldives [25]. In the Maldives, mating trains are reported to consist of 1 – 21 males chasing a single, fast swimming female. The number of females in the train increases then decreases before copulation takes place. Marshall & Bennett [31] reported strong lateralization of mating scars in females with 99% of the scars visible on the left pectoral fin. Yano et al. [37] reported mating scars on both wings of the female but only fresh scars were observed on the left wing.

Mating events appear to be restricted to certain times of the year but the time of year will vary by region [5, 25, 31]. Off Ogasawara Island, Japan, most mating trains were observed between March and October with occasional chases observed outside the summer season [37]. Mating behavior in Yaeyama Island was reported during the spring and autumn and lasting for about a one month duration [5]. The wet season in this area begins in May and lasts through June, and the typhoon season (May – November), typically peaks in September. In the Maldives, the majority of mating trains were observed between October and November, towards the end of their wet season (April to October), with occasional trains observed outside this season [25]. In Mozambique, fresh mating scars were observed primarily during the summer months [31]. In Hawaii, the mating season appears to be during the winter months [38]. Although mating trains can be reliably seen, acts of copulation in free ranging mantas are rare [31, 37].

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Food and Foraging

Manta rays appear to feed on small planktonic organisms such as euphasids, copepods, mysids, decapod larvae, and possibly shrimp, [2, 3, 6]. Stomach contents from an oceanic manta specimen from South Carolina contained fragments resembling the shells of shrimps as well as remnants of a small crab [2].

When feeding, mantas unfurl their cephalic fins to help direct the plankton rich water into their mouths and over the five pairs of gills. Finger-like projections on the gill arches, known as gill-rakers, strain and capture the food. This type of feeding is termed ram-jet feeding. They sometimes will swim in repeated summersaults through a dense patch of plankton. Coles [19] reported mobulids using their cephalic fins to heard small minnows up against the beach and funnel them into their mouth. And although manta rays have been reportedly seen gulping schools of small mullet [2], it is more likely that the mullet were simply feeding on the same patches of plankton targeted by the mantas.

Very little is known about the feeding behavior of resident mantas. They have been seen feeding during the daytime and at night, as single individuals, and in large aggregations. In some regions, artificial lights above and below the water are used to attract large amounts of zooplankton, which in turn attracts resident mantas looking to take advantage of an easy meal. Dive operators in Kona, Hawaii, have conditioned manta rays to aggregate each night around a group of scuba divers whose underwater lights serve to attract plankton into the area. The abundance of plankton is much less in the open ocean and tends to be more dense around upwellings and around island groups [39]. Nutrient rich upwellings induced by trade winds can also create conditions suitable for high primary production and thus may create important feeding areas for mantas [8]. Temperature is also implicated in the pattern of zooplankton diversity which is correlated closely with sea-surface temperature and decreases rapidly with depth [40]. Plankton are known to take regular and even daily vertical migrations [41] and manta rays may adjust their feeding regime in order to take advantage of these diel cycles. In Bateman Bay, Western Australia, resident manta rays are observed feeding about 40% of the time, throughout the year, on small calanoid copepods [27].

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Status and Conservation

Natural Predators

Large sharks [5] and killer whales (Orcinus orca) [42] have been reported to prey on manta rays. It is unknown how many attacks result in fatalities and weather or not the shark will consume the entire manta ray. In Mazambique, about 1 in 8 manta rays shows injuries likely caused by a shark attack [17], compared with only 1 in 4 in the Maui, Hawaii population [38]. Cookie cutter shark bites have also been observed on mantas, most likely occurring at night during deeper dives [5].

Anthropogenic Threats

The status of most manta ray populations worldwide is poorly understood. They are classified by the IUCN Red List for Threatened Animals as “near-threatened” [43],  meaning that manta rays could be threatened with extinction in the near future if conservation efforts are not implemented (see details).

The number of manta rays that exist worldwide is unknown, and little is known about their population ecology. The recent reclassification of the genus has new implications for the conservation assessment of both species [1]. Each population and population stock faces its own regional specific ecological pressures. Understanding how a particular population or population stock is affected by anthropogenic impacts in its region is critical to understanding its conservation status and for directing effective management.

Directed Fisheries

Traditional hunting for Mantas in places like eastern Australia and the Sea of Cortez (Gulf of California), involved fishers on small boats harpooning slow swimming animals traveling just below the surface. They were hunted for their skin, the oil from their large livers, and simply for shark bait, but never in enough quantity to be of commercial importance [2]. More recently, large international markets have emerged for shark fins, meat, and hides, resulting in the rapid rise in value for shark products. A new market has also emerged in Asia, creating a demand for dried manta gill rakers to be used in traditional Chinese medicines and in the treatment of cancer [44]. These demands, combined with the existing demand for manta ray cartilage to be used as filler in shark fin soup [45, 46], has led to an exponential increase in the Indonesian fishery in just a few years, threatening to drive manta ray populations into commercial extinction [47, 48]. In addition, as a result of over-fishing, fishermen have turned to hunting Mantas as an alternative source of income, leading to a ten-fold increase in manta ray harvesting.

These directed fisheries targeting manta rays have caused populations to decline and even disappear in areas such as Mexico [5, 49], the Philippines [45], Indonesia [47, 48], India, Sri Lanka, and other parts of Southeast Asia [43]. An estimated 1,500 manta rays were taken over a period of six months in Lamakera, Indonesia [50]. Drift gill nets 700 – 1000 m long and 35 m high are set 7 m below the water surface during the migratory passage of mobulids and are reported to entrap as many as 50 manta rays in a single net [5]. Divers from Palawan Island, Philippines, reported that the local manta ray population had been reduced to a third of its original population over a seven year period [5]. In Yaeyama Island, Japan, common aggregations of 50 manta rays in 1982 were reduced to just 30 in 1992, and further reduced to no more than 15 by 1999 [5].

In Hawaii, it appears that about 1 in 10 manta rays in the population have an amputated or non-functioning cephalic fin, most likely due to entanglement in monofilament line [38]. Considering the function of the cephalic fins to guide food into the mouth during feeding, an animal reduced to a single cephalic fin would likely suffer a reduction in feeding efficiency. It is not uncommon to observe a manta ray in Hawaii with either fish hooks embedded in their cephalic fins, fishing line wrapped around a cephalic fin, or fishing line scars around a cephalic fin and the pectoral fin, providing further support that entanglement in fishing lines is a significant threat. Further research is needed to determine the impaired fitness of a manta ray reduced to only a single cephalic fin. This could be achieved by monitoring their growth and reproductive success over time.

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Mooring and Anchor Lines

Although rare, manta rays on occasion entangle themselves in anchor and mooring lines. It is believed that when a line makes contact with the front of the head between the cephalic fins, the reflexive response by the manta is to immediately close the cephalic fins, thereby trapping the rope and entangling the manta ray when they begin to roll in an attempt to get free. This hypothesis was recently supported by video footage of a manta ray colliding with a cameraman and swimming off with the camera after locking its cephalic fins around the camera. Bigelow & Schroeder [2] documented several records of a manta ray entangling in an anchor line in the same way, sometimes towing the boat along for some distance. On at least two occasions, a manta ray in Hawaii was reported to perish after entangling in a mooring line (Hawaii, 2007, 2008).

Ecotourism

In light of diminishing populations of manta rays from directed fisheries, new interest has sparked in the area of ecotourism as an alternative and more sustainable use of the resource. Homma et al. [5] estimated a dead manta ray sells for about $400 US in the Philippines and would provide the nation with a total annual revenue of $4,800,000 US. An alternative would be a switch to ecotourism, with tourists paying about $400 US each to view manta rays in the wild. About 12,000 tourists annually would be needed to generate the same type of revenue gained from direct hunts and the practice becomes sustainable as the resource becomes renewable.

The development of manta ray viewing ecotours is becoming a popular recreational activity and a booming industry in many parts of the world where manta rays are known to aggregate [15, 37]. These programs can generate tens of thousands and even tens of millions of dollars of tourist revenue to local communities annually. However, unregulated, these operations can impose undue stress on the local manta ray population, potentially causing the animals to abandon the area. Sustained pressure from divers, snorkelers, boaters, and jet skiers visiting a manta ray aggregation site in Bora Bora, French Polynesia, reportedly caused the manta rays to completely abandon this area [23].

The biological significance of displacing manta rays from these aggregation sites is unknown and worthy of investigation. A study conducted by Semeniuk [51] in which tourists interacted with a wild population of southern stingrays (Dasyatus americana) resulted in higher parasite loads, higher injury rates, and suppression of the immune system in these animals, putting their long-term survival at serious risk. Some governments are requiring licenses to operate these ecotours to help ensure that it does not damage the resource upon which it relies.

Boat Traffic

Manta rays can be frequently observed traveling just below the surface and will often approach or show little fear towards man or vessel [19], which can also make them extremely vulnerable to boat strikes by vessels traveling at high speed and unaware of an animal in their path. Several manta rays aggregating in Ningaloo Reef, Western Australia, possess deep scars where they were most likely struck by a boat propeller (F. McGregor pers. Comm.. 2007). Another incident was reported in Hawaii in which a manta ray died due to injuries sustained to the head from a boat propeller (T. Clark, pers. Comm. 2006).

In the Florida Keys, a cooperative effort between the National Park Service and NOAA’s Florida Key Marine Sanctuary restricted boat traffic through a nurse shark mating and nursery ground by using navigation control buoys during the peak of the mating season (Carrier & Pratt 1998). They found that the presence of boats during mating activities of nurse sharks were disruptive and often resulted in unsuccessful mating attempt.

Aquariums

Recent success in Japan’s manta ray captivity program [52] has sparked global interest from aquariums looking to add manta rays to their exhibits. The Okinawa Ocean Expo in Motobu, Okinawa Island, Japan, is the only aquarium in the world that has successfully housed and bred resident manta rays [30]. The Atlantis Resort in the Bahamas [53] and more recently the Georgia Aquarium are the only two facilities in the Western Hemisphere to keep Mantas in captivity. The manta rays on display at the Atlantis Resort are removed from the wild and housed temporarily before being returned back to the wild.

The minimum number of aquariums worldwide housing manta rays is a product of the difficulty in keeping manta rays alive during captivity. In certain aggregation areas where manta rays are easily accessible, and where no regulatory protection exists, populations may be exposed to indiscriminant non-sustainable extraction of individuals for profit, especially those that are small and geographically isolated.

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Manta Ray Protection

In many parts of the world, measures have been taken to reduce anthropogenic threats on local manta ray populations. For example, codes of conduct for manta ray dive operators have been implemented in Kona, Hawaii (unpublished), Western Australia (Daw & McGregor 2008), Mozambique (A. Marshall, pers. comm.), Bora Bora (M. deRosemont, pers. Comm.), and in the Maldives (G. Stevens, pers. comm.). Elements of the code include minimizing the number of divers around the manta rays, keeping divers in tight controlled groups, restricting the touching of the animals, and using approach methods that minimize stress on the manta rays. In Mozambique, mooring balls are banned in areas where the manta rays are known to aggregate, and boats are required to minimize their speed. Marine protected areas (MPA) have been established in the Maldives, Mexico, Mozambique, and Yap, to help eliminate fishing pressure and provide a safe refuge for the manta rays. 

In Hawaii, a state law was passed that prevents the intentional killing or extraction of manta rays from all Hawaiian State waters with an exception for persons granted a special take permit. A special take permit requires the applicant to demonstrate the potential biological removal (PBR) of the targeted population prior to approval. PBR is the maximum number of animals, not including natural mortalities, which may be removed from a stock while allowing that stock to reach or maintain its optimum sustainable population [54].

Fortunately in Hawaii, manta rays are not hunted commercially. Due to their small population sizes and very localized movements, a Manta ray fishery in Hawaii could never be sustainable. With proper codes of conduct, “swim-with manta ray” ecotours are a much more sustainable alternative to commercial hunts. Manta ray night dive operations off Kona, Hawaii, produce over 2.5 million in revenues annually through eco-tourism. In contrast, a single dead manta ray in Indonesia sells for approximately $160 [47], or about $545 in Indonesia [48].

Research

In contrast to sharks, which have been the subject of numerous research studies, little research has been done on manta rays. This difference is primarily due to the difficulty in studying these large animals in the field. Landings from fisheries provide a source of information on morphology, including the size demographics of a fished population, descriptions on the size at sexual and physical maturity, litter sizes, and other important reproductive information. Satellite, acoustic, and pop-up archival tags are becoming more common for tracking animals that travel large distances and can provide valuable information on home ranges, dive profiles, and diel patterns of behavior. Mark recapture studies are useful for estimating a population size and range, and for developing individual life histories.

Increased data collection efforts worldwide are producing a valuable global database, providing information on manta ray populations, movements, habitat use, and behavior. Further information on the migration patterns, levels of abundance among regions and habitat preferences are necessary for global management and conservation strategies. A better picture of worldwide populations is necessary for conservation efforts both within local communities and on an international level.

While whales, dolphins, and sharks have been the focus of scientific study, little research is being conducted on Mantas. The Pacific Manta Research Group has been using direct observation and photo-identification as the main research tools to monitor Manta populations in the Sea of Cortez, and the Revillagigedo Islands south of Baja. The Manta Sight Project in Australia is collecting sighting records of Mantas for the Great Barrier Reef. The Nature Conservancy and Pfleger Institute of Environmental Research (Pier) are doing studies in Komodo Marine Park, Indonesia. Andrea Marshall (Manta & Whale Shark Research Centre) is investigating one of the  largest manta ray populations ever studied off Mozambique, Africa. Keller and Wendy Laros, founders of the Manta Pacific Research Foundation in Kona, Hawaii, are working closely with Tim Clark of the University of Hawaii to monitor the movements of about 140 manta ray. Mark Deakos with HAMER completed his doctoral work studying the ecology of a manta ray population of over 300 individuals in Maui, Hawaii (see Maui's manta rays). Tourism revenues for the tiny island of Yap in Micronesia have also initiated identification efforts by dive operators in this region.

The recent differentiation of the genus Manta into two separate species raises new concerns about anthropomorphic impacts placed on highly resident populations. Due to the slow population growth and low fecundity typical of elasmobranchs [55], monitoring of changes in population size, population growth, and impact on these parameters from anthropogenic impacts are recommended. An understanding of population characteristics and basic ecological information is needed on a regional basis.

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Literature Cited

1.         Marshall, A., L. Compagno, and M. Bennett, Redescription of the genus Manta with resurrection of Manta alfredi (Krefft,1868) (Chondrichthyes; Myliobatoidei; Mobulidae). Zootaxa, 2009. 2301: p. 1–28.
2.         Bigelow, H. and W.C. Schroeder, Fishes of the western North Atlantic. Sawfishes, guitarfishes, skates, rays, and chimaeroids. Mem. Sears Found. Mar. Res., 1953. 1: p. 500-514.
3.         Last, P. and J. Stevens, Sharks and rays of Australia. 2nd ed. 1994, Melbourne, Australia: CSIRO Publishing.
4.         Marshall, A.D., S.J. Pierce, and M.B. Bennett, Morphological measurements of manta rays (Manta birostris) with a description of a foetus from the east coast of Southern Africa. Zootaxa, 2008. 1717: p. 24-30.
5.         Homma, K., et al. Biology of the manta ray, Manta birostris Walbaum, in the Indo-Pacific. in Indo-Pacific fish biology: proceedings of the fifth international conference on Indo-Pacific fishes, Noumea, 1997. 1999. France: Ichthyological Society of France.
6.         Clark, T.B., Population Structure of Manta birostris (Chondrichthyes: mobulidae) from the Pacific and Atlantic Oceans, in Wildlife and Fisheries Sciences. 2001, Texas A&M University: Galveston, Texas. p. 68.
7.         Kitchen-Wheeler, A., Manta Rays: Research in the Maldives. Shark Focus, 2008. 31: p. 4.
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12.       Alexander, R., Evidence of brain warming in the mobulid rays, Mobula tarapacana and Manta birostris (Chondrichthyes: Elasmobranchii: Batoidea: Myliobatiformes). Zoological Journal of the Linnean Society, 1996. 118(2): p. 151-164.
13.       Bleckmann, H. and M. Hofmann, Special senses, in Sharks, skates, and rays: The biology of elasmobranch fishes, W.C. Hamlett, Editor. 1999, The Johns Hopkins Univeristy Press: Baltimore, MD. p. 300-328.
14.       Cadenat, J., Les diables de mer. Notes Africaines, 1958. 80: p. 116-120.
15.       Dewar, H., et al., Movements and site fidelity of the giant manta ray, Manta birostris, in the Komodo Marine Park, Indonesia. Marine Biology, 2008. 155(2): p. 121-133.
16.       Kitchen-Wheeler, A.-M., Migration Behaviour of the Giant Manta (Manta birostris) in the Central Maldives Atolls in 2008 Joint Meeting of Ichthyologists and Herpetologists, M.A. Donnelly, Editor. 2008: Montreal, Canada. p. 244.
17.       Marshall, A.D., Biology and population ecology of Manta birostris in southern Mozambique. 2009, University of Queensland.
18.       Losey Jr, G., The ecological importance of cleaning symbiosis. Copeia, 1972. 1972(4): p. 820-833.
19.       Coles, R.J., Natural history notes on the devil fish, Manta birostris (Walbaum) and Mobula ofersi (Muller). Bull. Amer. Mus. Nat. Hist., 1916. 35: p. 649-657.
20.       Coté, I., Evolution and ecology of cleaning symbioses in the sea. Oceanography and Marine Biology, 2000. 38: p. 311-355.
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