Manta birostris

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	CHONDRICHTHYES	RAJIFORMES	MOBULIDAE

Scientific Name:

Manta birostris

Species Authority:

(Donndorff, 1798)

Common Name/s:

English	–	Devil Fish, Devil Ray, Giant Manta, Manta Ray, Prince Alfred’s Ray
French	–	Raie Manta
Spanish	–	Manta Raya

Taxonomic Notes:

The authority for Manta birostris is often incorrectly ascribed to Walbaum (1792) (Ebert 2003). The correct citation is Manta birostris (Donndorff 1798).Genus previously thought to contain multiple species, now considered monotypic by most authors. However, the genus is still in need of world-wide review. Mitochondrial DNA sequence data does not support species level differentiation between Atlantic or Pacific individuals, between individuals in the Pacific, or between individuals with predominantly black or predominantly white ventral coloration (T. Clark, Masters Thesis, Texas A&M; University, 2002). Manta rays are often confused with rays of the genus Mobula, and care should be used to ensure reports of mantas are actually of Manta birostris and not its sister genus. Manta is distinguished from Mobula by the terminal position of its mouth and the absence of teeth in the upper jaw (Last and Stevens 1994, Nelson 1994).

Assessment Information [top]

Red List Category & Criteria:

Near Threatened ver 3.1

Year Assessed:

2006

Assessor/s

Marshall, A., Ishihara, H., Dudley, S.F.J., Clark, T.B., Jorgensen, S., Smith, W.D. & Bizzarro, J.J.

Evaluator/s:

Kyne, P.M., Notarbartolo di Sciara, G., Fowler, S.L. & Compagno, L.J.V. (Shark Red List Authority)

Justification:
Manta birostris is a large plankton-feeding ray, widely distributed in tropical and semi-tropical shelf waters, around oceanic islands and other areas of upwelling, such as seamounts. Unfished populations are not thought to be threatened, however it is not well understood how their use of inshore areas around inhabited coastlines might be affected by anthropogenic influences such as pollution, coastal development, and eco-tourism pressures.

Only a few directed fisheries exist for manta rays within their range and they do not, in most areas, make-up large percentages of bycatch in non-target fisheries. Their large size, slow speed, and tendency to be found on the surface make manta rays an easy target for fishermen. Target fisheries for this species do currently exist in several countries, including the Philippines, Mexico, Mozambique, Madagascar, India, Sri Lanka, Brazil, Tanzania and Indonesia. Many parts of the manta are used for local and export trade including their fins, skin, liver, meat, and branchial filaments. Recent demand for branchial filaments, which are dried and exported for the Asian medicinal market, has resulted in dramatic increases in fishing pressure for mobulids, including mantas, throughout South East Asia and Eastern Africa, causing a switch from subsistence fisheries to commercial export fisheries. Manta rays are also a by-catch in unknown numbers in the tuna purse seine fisheries as well as in other fisheries and shark protection net programs.

Population declines have been observed in the Philippines, Mexico, Sri Lanka/India, and Indonesia. Although catch data are not available in many of the areas where manta rays are fished, small population size and limited migration increases the risk of local extinction with limited potential for populations to re-establish themselves. Regional population declines have been recorded in areas where the species has been fished, including the South China and Sulu Seas, the Philippians, Indonesia and on the west coast of Mexico.

The existence of anthropogenic pressures (i.e., direct/indirect fisheries, pollution, and exploitation of coastal environments) in areas supporting critical habitats like breeding, birthing, and nursery grounds (eg., Mozambique, Bora Bora, French Polynesia) is yet another threat to populations which congregate in mass numbers in these areas or use them as refuges for their young. Increased densities of individuals during certain seasons, combined with their ease of capture and the lack of regulated fishing management, may result in unsustainable fishing pressure during these times.

Like many elasmobranchs, manta rays are highly vulnerable to fisheries given their life history and population structure. Manta rays are known to live in excess of 20 years. Mantas have low fecundity, giving live birth to a single pup, possibly two pups on occasion.

Some populations of mantas, like those in the Hawaiian Islands and the Island of Yap have a closed population structure, with high site fidelity and little to no migration away from island groups. Other studies on populations with year-round sightings and high re-sighting rates reveal that a portion of the population is resident while a subset of the population appears to engage in larger migrations. In a few sites, mantas have been well documented to be seasonal. Because different populations show differences in movement habits and site fidelity, management for this species needs to be site specific. Fishing pressures will have a significant and potentially irreversible effect on closed populations due mainly to the inability for these populations to re-establish themselves. On the other hand, management plans for areas with open populations will have to include all other parts of their home range to be effective.

History:

2002	–	Data Deficient (IUCN 2002)
2000	–	Lower Risk/least concern (Hilton-Taylor 2000)

Geographic Range [top]

Range Description:	Circumglobal in temperate and tropical waters. Largest populations occur along areas of continental shelves supported by upwelling, in island chains, and near seamounts. Observed primarily in near-shore waters. Found in the west Atlantic from North Carolina, USA to northern Brazil, east Atlantic from the Canary Islands to Liberia, Indian Ocean from South Africa to western Australia (including the Red Sea), northern New Zealand, west Pacific from eastern Australia to the Izu Peninsula, Japan, central Pacific from New Caledonia, Tahiti to Hawaii Islands and in the east Pacific from Santa Barbara, California to Peru including the Galapagos Islands and Cocos Island (Bigelow and Schroeder 1953, Last and Stevens 1994, Grove and Lavenberg 1997, Duffy and Abbott 2003, Ebert 2003, H. Ishihara unpub. data).
Countries:	Native: Angola; Aruba; Australia; Belize; Bermuda; Brazil; British Indian Ocean Territory (Chagos Archipelago); Cape Verde; Cayman Islands; China; Christmas Island; Cocos (Keeling) Islands; Colombia; Cook Islands; Cuba; Djibouti; Ecuador (Galápagos); Egypt; El Salvador; French Polynesia; Guam; Guatemala; Guinea; Guinea-Bissau; Guyana; Honduras; India; Indonesia; Jamaica; Japan; Madagascar; Malaysia; Maldives; Marshall Islands; Mauritania; Mauritius; Mexico; Mozambique; Netherlands Antilles (Curaçao); New Caledonia; New Zealand; Nicaragua; Northern Mariana Islands; Oman; Palau; Panama; Papua New Guinea; Peru; Portugal (Madeira); Réunion; Saudi Arabia; Senegal; Seychelles; Sierra Leone; Solomon Islands; Somalia; South Africa; Spain (Canary Is.); Suriname; Taiwan, Province of China; Thailand; Trinidad and Tobago; United States (California, Florida, Hawaiian Is., North Carolina, South Carolina); Vanuatu; Venezuela; Viet Nam; Virgin Islands, U.S.; Yemen
FAO Marine Fishing Areas:	Native: Atlantic – eastern central; Atlantic – western central; Atlantic – northwest; Atlantic – southeast; Atlantic – southwest; Indian Ocean – western; Indian Ocean – eastern; Pacific – southwest; Pacific – northeast; Pacific – southeast; Pacific – eastern central; Pacific – western central

Population [top]

Population:	Photo identification studies suggest local population sizes in the order of 50 to 350 individuals (R. Rubin, pers. comm., Revillagigedos Islands, Mexico; Tim Clark, unpublished data, Hawaii; Andrea Marshall, unpublished data, Tofo, Mozambique; Mocava de Rosemont, pers. comm., Bora Bora, French Polynesia; Bill Acker, pers. comm., Yap Island; Takashi Itoh, pers. comm., Yaeyama Islands, Japan; Paul Ahuja, pers. comm.). A colour variant of the species whose ventral side is dark is called “Black Manta” (Barton 1948, Homma et al. 1997) which may represent up to 25% of the total population in some areas but is quite rare in others (Homma et al. 1999, R. Rubin pers. comm., Revillagigedos Islands, Mexico). Albino individuals of the manta ray have been found in Sumbawa Island, Indonesia and northern Borneo, Malaysia (Ishihara et al. 2001). Populations appear to be stable in Hawaii, Yap and Japan, but may be declining in Mexico, the Philippines, Indonesia, India, Sri Lanka, and other parts of Southeast Asia where they are fished. In the Gulf of California (Mexico) in 2003, zero individuals were sighted (P. Ahuja, pers. comm.). Based on data from 2001 and 2002 alone, Chapman and Peterson mark-recapture estimates indicate a local population of approximately 177 to 220 individuals in the Gulf of California. The observation of zero sightings in 2003 is unexplained but may be of concern. Mantas are now reported to be rare in the Philippines, especially around the Bohol Sea where a major manta fishery was centred. Additionally, Japanese sports divers suggest that the population of manta rays at one site in the Sulu Sea (probably part of the same population fished at Pamilacan Island, Philippines) fell by one half to two-thirds in seven years from the end of the 1980s (Michiyo Nishitani, pers. comm. 1996). Data from observations in Okinawa Island by T. Itoh suggest that the number of individuals in a school is decreasing from 30 to 50 in the 1970’s to at most 14 to 15 in the 1990’s (Homma et al. 1999). Some populations of mantas, like those in the Hawaiian Islands and the Island of Yap, have a closed population structure with high site fidelity and little to no migration away from island groups (Tim Clark, unpublished data, Hawaii; Bill Acker, pers. comm., Yap Island). Other studies on populations with year-round sightings and high re-sighting rates reveal that a portion of the population is resident while a subset of the population appears to undertake larger migrations (Homma et al. 1999, Andrea Marshall, unpublished data, Tofo, Mozambique), Mocava de Rosemont, pers. comm., Bora Bora, French Polynesia). Annual migration range in Japan has been documented to 350 km (Ishihara and Homma 1995). In a few sites, mantas have been well documented to be seasonal (Kathy Townsend, pers. comm., North Stradbroke Island (Australia), R. Rubin, pers. comm., Revillagigedos Islands, Mexico). Observations on mantas frequenting remote seamounts in Socorro (Mexico), Malpelo (Ecuador) and off some remote island groups (Cocos Island, Costa Rica; Galapagos, Ecuador) show a degree of philopatry to these sites but also indicate that these mantas make migrations away from these areas during parts of the year (R. Rubin pers. comm., Andrea Marshall unpublished data). Acoustic tracking in Hawaii suggests that mantas rarely venture from coastal waters, and migrate on a regular basis between several cleaning stations and feeding areas (Tim Clark unpublished data). Many preliminary reports from population studies on manta rays suggest the existence of small populations with a high degree of visitation to or occurrence in specific areas and critical habitats (Tim Clark, unpublished data, Hawaii; Andrea Marshall, unpublished data, Tofo, Mozambique; Bill Acker, pers. comm. Yap Island). Results also suggest a high degree of fragmentation between populations.
Population Trend:	Unknown

Population:

Photo identification studies suggest local population sizes in the order of 50 to 350 individuals (R. Rubin, pers. comm., Revillagigedos Islands, Mexico; Tim Clark, unpublished data, Hawaii; Andrea Marshall, unpublished data, Tofo, Mozambique; Mocava de Rosemont, pers. comm., Bora Bora, French Polynesia; Bill Acker, pers. comm., Yap Island; Takashi Itoh, pers. comm., Yaeyama Islands, Japan; Paul Ahuja, pers. comm.). A colour variant of the species whose ventral side is dark is called “Black Manta” (Barton 1948, Homma et al. 1997) which may represent up to 25% of the total population in some areas but is quite rare in others (Homma et al. 1999, R. Rubin pers. comm., Revillagigedos Islands, Mexico). Albino individuals of the manta ray have been found in Sumbawa Island, Indonesia and northern Borneo, Malaysia (Ishihara et al. 2001).

Populations appear to be stable in Hawaii, Yap and Japan, but may be declining in Mexico, the Philippines, Indonesia, India, Sri Lanka, and other parts of Southeast Asia where they are fished. In the Gulf of California (Mexico) in 2003, zero individuals were sighted (P. Ahuja, pers. comm.). Based on data from 2001 and 2002 alone, Chapman and Peterson mark-recapture estimates indicate a local population of approximately 177 to 220 individuals in the Gulf of California. The observation of zero sightings in 2003 is unexplained but may be of concern. Mantas are now reported to be rare in the Philippines, especially around the Bohol Sea where a major manta fishery was centred. Additionally, Japanese sports divers suggest that the population of manta rays at one site in the Sulu Sea (probably part of the same population fished at Pamilacan Island, Philippines) fell by one half to two-thirds in seven years from the end of the 1980s (Michiyo Nishitani, pers. comm. 1996). Data from observations in Okinawa Island by T. Itoh suggest that the number of individuals in a school is decreasing from 30 to 50 in the 1970’s to at most 14 to 15 in the 1990’s (Homma et al. 1999).

Some populations of mantas, like those in the Hawaiian Islands and the Island of Yap, have a closed population structure with high site fidelity and little to no migration away from island groups (Tim Clark, unpublished data, Hawaii; Bill Acker, pers. comm., Yap Island). Other studies on populations with year-round sightings and high re-sighting rates reveal that a portion of the population is resident while a subset of the population appears to undertake larger migrations (Homma et al. 1999, Andrea Marshall, unpublished data, Tofo, Mozambique), Mocava de Rosemont, pers. comm., Bora Bora, French Polynesia). Annual migration range in Japan has been documented to 350 km (Ishihara and Homma 1995). In a few sites, mantas have been well documented to be seasonal (Kathy Townsend, pers. comm., North Stradbroke Island (Australia), R. Rubin, pers. comm., Revillagigedos Islands, Mexico). Observations on mantas frequenting remote seamounts in Socorro (Mexico), Malpelo (Ecuador) and off some remote island groups (Cocos Island, Costa Rica; Galapagos, Ecuador) show a degree of philopatry to these sites but also indicate that these mantas make migrations away from these areas during parts of the year (R. Rubin pers. comm., Andrea Marshall unpublished data).

Acoustic tracking in Hawaii suggests that mantas rarely venture from coastal waters, and migrate on a regular basis between several cleaning stations and feeding areas (Tim Clark unpublished data). Many preliminary reports from population studies on manta rays suggest the existence of small populations with a high degree of visitation to or occurrence in specific areas and critical habitats (Tim Clark, unpublished data, Hawaii; Andrea Marshall, unpublished data, Tofo, Mozambique; Bill Acker, pers. comm. Yap Island). Results also suggest a high degree of fragmentation between populations.

Population Trend:

Unknown

Habitat and Ecology [top]

Habitat and Ecology:	Circumglobal in temperate and tropical waters. Largest populations occur along areas of continental shelves supported by upwelling, in island chains, and near seamounts. Observed primarily in near shore waters. Although Manta birostris is circumglobally distributed in tropical and warm temperate waters, very little is known of the species’ life history or ecology. Most often they are sighted while frequenting cleaning stations on inshore reefs, where they possibly have parasites removed or their skin and wounds cleaned (A. Marshall unpublished data, T. Clark unpub. data, B. Rubin pers. comm). They are also seen frequently, in areas of high productivity where they often collectively come to feed. The main prey of the manta ray is planktonic crustacea and small bony fishes. Sharks and possibly killer whales are the main natural predators (Michael 1993, Ishihara and Homma 1995, Andrea Marshall unpub. data, Mozambique). Manta rays are known to live in excess of 20 years (Homma et al. 1999, R. Rubin, unpub. data, Revillagigedos Islands, Mexico). Mating occurs in Mozambique and other parts of southern hemisphere distribution (Yap Islands, Bora Bora, French Polynesia, and Australia) from November-January based on witnessed mating events, courtship behaviour and swollen and scarred claspers in males (Andrea Marshall, unpublished data, Tofo, Mozambique; Mocava de Rosemont, pers. comm., Bora Bora, French Polynesia; Tim Rock pers. comm., Yap). Mating behaviour and copulation events have been witnessed in May-June in the northern hemisphere (Ogasawara Islands, Japan: Yano et al. 1999). Mantas, like other myliobatiform rays, possess a highly specialized form of aplacental viviparity in which embryos are nourished via uterine villi that secrete a thick, protein/lipid rich liquid termed histotrophe (Wourms 1977). Reproductive potential of the species is extremely limited due to single functional uterus and an average fecundity of one (Bigelow and Schroeder 1953, Homma et al. 1999), although litters of two have apparently been reported (Ebert 2003). Gestation period is estimated to be between 10 and 14 months (Homma et al. 1999; Andrea Marshall, unpublished data, Tofo, Mozambique; Mocava de Rosemont pers. comm. Bora Bora, French Polynesia). Largest recorded embryo size 1.27 m DW (Bigelow and Schroeder 1953) and smallest recorded free-swimming individual between 1.2 and 1.5 m DW (Homma et al. 1999, Andrea Marshall, unpublished data, Tofo, Mozambique, Mocava de Rosemont pers. comm. Bora Bora, French Polynesia). Mature females have been documented to give birth annually in some populations (Mocava de Rosemont pers. comm., Bora Bora, French Polynesia) where other populations have not recorded pregnancies in consecutive years in any of the mature females (Homma et al. 1999, Andrea Marshall, unpublished data, Tofo, Mozambique). The smallest females confirmed to be mature from recorded pregnancies in the field or from dissections are 4.0 to 4.5 m DW (Bigelow and Schroeder 1953, Andrea Marshall, unpublished data, Tofo, Mozambique, Mocava de Rosemont, pers. comm. Bora Bora, French Polynesia). Age at maturity in male mantas in Hawaii appears to be 6 to 8 years based on time for claspers to extend past the pelvic fins (Tim Clark, unpublished data) and 3.5 to 4 m DW in Mozambique (Andrea Marshall, unpub. data).
Systems:	Marine

Habitat and Ecology:

Circumglobal in temperate and tropical waters. Largest populations occur along areas of continental shelves supported by upwelling, in island chains, and near seamounts. Observed primarily in near shore waters.

Although Manta birostris is circumglobally distributed in tropical and warm temperate waters, very little is known of the species’ life history or ecology.

Most often they are sighted while frequenting cleaning stations on inshore reefs, where they possibly have parasites removed or their skin and wounds cleaned (A. Marshall unpublished data, T. Clark unpub. data, B. Rubin pers. comm).

They are also seen frequently, in areas of high productivity where they often collectively come to feed. The main prey of the manta ray is planktonic crustacea and small bony fishes. Sharks and possibly killer whales are the main natural predators (Michael 1993, Ishihara and Homma 1995, Andrea Marshall unpub. data, Mozambique).

Manta rays are known to live in excess of 20 years (Homma et al. 1999, R. Rubin, unpub. data, Revillagigedos Islands, Mexico).

Mating occurs in Mozambique and other parts of southern hemisphere distribution (Yap Islands, Bora Bora, French Polynesia, and Australia) from November-January based on witnessed mating events, courtship behaviour and swollen and scarred claspers in males (Andrea Marshall, unpublished data, Tofo, Mozambique; Mocava de Rosemont, pers. comm., Bora Bora, French Polynesia; Tim Rock pers. comm., Yap). Mating behaviour and copulation events have been witnessed in May-June in the northern hemisphere (Ogasawara Islands, Japan: Yano et al. 1999).

Mantas, like other myliobatiform rays, possess a highly specialized form of aplacental viviparity in which embryos are nourished via uterine villi that secrete a thick, protein/lipid rich liquid termed histotrophe (Wourms 1977). Reproductive potential of the species is extremely limited due to single functional uterus and an average fecundity of one (Bigelow and Schroeder 1953, Homma et al. 1999), although litters of two have apparently been reported (Ebert 2003).

Gestation period is estimated to be between 10 and 14 months (Homma et al. 1999; Andrea Marshall, unpublished data, Tofo, Mozambique; Mocava de Rosemont pers. comm. Bora Bora, French Polynesia). Largest recorded embryo size 1.27 m DW (Bigelow and Schroeder 1953) and smallest recorded free-swimming individual between 1.2 and 1.5 m DW (Homma et al. 1999, Andrea Marshall, unpublished data, Tofo, Mozambique, Mocava de Rosemont pers. comm. Bora Bora, French Polynesia). Mature females have been documented to give birth annually in some populations (Mocava de Rosemont pers. comm., Bora Bora, French Polynesia) where other populations have not recorded pregnancies in consecutive years in any of the mature females (Homma et al. 1999, Andrea Marshall, unpublished data, Tofo, Mozambique). The smallest females confirmed to be mature from recorded pregnancies in the field or from dissections are 4.0 to 4.5 m DW (Bigelow and Schroeder 1953, Andrea Marshall, unpublished data, Tofo, Mozambique, Mocava de Rosemont, pers. comm. Bora Bora, French Polynesia). Age at maturity in male mantas in Hawaii appears to be 6 to 8 years based on time for claspers to extend past the pelvic fins (Tim Clark, unpublished data) and 3.5 to 4 m DW in Mozambique (Andrea Marshall, unpub. data).

Systems:

Marine

Threats [top]

Major Threat(s):	Throughout most of their range there are neither directed fisheries for manta rays nor do they make-up large percentages of bycatch in non-target fisheries. However, their large size, slow speed, and tendency to be found on the surface make manta rays an easy target for fishermen. The main threats for this species are fishing activities where mantas are targeted or caught as bycatch. Recent demand for their fins and for their liver and branchial filaments, used in traditional Chinese medicine, has increased fishing activity worldwide for this species.Target fisheries for this species currently exist in several countries, including the Philippines, Mexico, Mozambique, Madagascar, India, Sri Lanka, Brazil, Tanzania and Indonesia (Notarbartolo di Sciara 1987, Alava and Trono 2002, Sea Watch, Portland, Oregon, pers. comm. 1996, H. Dewar, pers. comm., A. Marshall, unpublished data (Mozambique), William White, pers. comm. (Indonesia)). Traditionally, in many of these areas of South East Asia, Eastern Africa, and Mexico, target fisheries for this species was for local consumption. In Madagascar, Tanzania and Mozambique, mantas were and are occasionally fished in artisanal gillnets and with harpoons. The flesh is primarily used for local consumption (Bianchi 1985, Jiddawi and Stanley 1999, Cooke 2003, Antananarivo 2003, A. Marshall, unpub. data, N. Jiddawi and S. Yahya, Institute of Marine Sciences, (Zanzibar) pers. comm.; and S. Semesi, TRAFFIC – Tanzania, pers. comm.). Isolated reports of fishing for mantas have continued in the Gulf of California. Artisanal pelagic gillnet fishermen throughout the Gulf of California have been observed to retain mantas as bait as well as utilize landed specimens for personal consumption and sale of meat. Many parts of the manta (skin, liver, fins and dried branchial filaments) are used for local and export trade. The recent increase in the demand for many of these parts has resulted in dramatic increases in fishing pressure for mobulids, including mantas, throughout South East Asia and Eastern Africa, causing a switch from a subsistence fisheries to a commercial export fisheries (Alava and Trono, 2002; A. Marshall, unpublished data (Mozambique)). In the Pamilacan Island, Philippines, it was reported that approximately 1,000 rays, including the manta ray and a few species of the genus Mobula, were taken between December 1995 and May 1996 by local fishermen using drift nets or harpoon. As a result, fishing was banned in the Philippines in 1998, but this ban was lifted in 1999 due to pressure from fishermen and lack of data on the fishery. During a yearlong survey, from March 2002 to March 2003, 156 manta rays (M. birostris) were caught, mostly in the months from November to January. Since the study, the ban has been re-established for M. birostris. Mantas are now reported to be rare in the Philippines, especially around the Bohol Sea where the fishery was focused. Additionally, Japanese sports divers suggest that the population of manta rays at one site in the Sulu Sea (probably part of the same population fished at Pamilacan Island, Philippines) fell by one half to two-thirds in seven years from the end of the 1980s. (Michiyo Nishitani, pers. comm. 1996). Data from observations in Okinawa Island by T. Itoh, the number of schooling is decreasing from 50 to 30 in 1970s to at most 14 to 15 in 1990s (Homma et al. 1997). In 2002, the World Wildlife Fund sponsored a trip to the islands of Lamakera and Lamalera in Indonesia to assess the manta ray fishery. Both islands have had traditional subsistence fisheries for manta rays, however Lamakera started fishing for manta rays commercially around 1998. This fishery developed to supply a specific demand from Asia for dried brachial elements, which are used in traditional Chinese medicines. Dewar (2002) estimated traditional catch rates in the village of Lamakera to be 200–300 mantas per year, with catch rates in 2002 estimated at 1,050–2,400 per year. Fishermen indicate that they no longer catch mantas in the traditional areas and are having to travel further to find mantas, and the fishermen on Lamalera caught almost no mantas in 2001, suggesting a substantial decline in the local populations that overlap with the Lamakera fishing grounds. In Mexico, the species appears to be rare after several decades of fishing. Fishing was banned in Mexico in 2002, when the Mexican government issued Official Rules Regulating Shark and Ray Fisheries in Mexican Waters, making it illegal to capture or kill Manta birostris in Mexican waters. However, the ban was lifted three months after its implementation due to lack of consensus between the different stakeholders, environmental, and tourism sectors. As of 2004, the legislation is still undergoing reviews and changes and has not been enacted, but it still currently provides specific protection for mantas and mobulids in all Mexican waters and prohibits their possession and trade (version 6.2 - Proyecto de Norma Oficial Mexicana Proy-Nom-029-Pesc-2004, pesca responsable de tiburones y rayas. Especificaciones para su aprovechamiento, 2004). Mantas are protected in marine park designated areas within Mexican waters, primarily in the Revillagigedo biosphere, following enforcement of a fishing closure, which began in early 2002. Even in protected areas such as marine parks and no-catch zones, there is evidence from around the world that targeted fishing still exists for this highly sought after species. In Mexico, enforcement for manta protection has been somewhat suspect as many fishing boats have been observed and caught deploying loglines, gillnets and seines within the Revillagigedo biosphere, which extends as a 12 mile buffer around each of the islands in the archipelago. Mantas have also been targeted in the Komodo Marine Park, very close to Lamakera, despite regulations forbidding fishing. Local dive operators and park rangers report a decline in abundance in the park (H. Dewar, pers. comm.). Manta rays are also a by-catch in unknown numbers in the tuna purse seine fisheries as well as in other fisheries (Sri Lankan Gill Net Fishery) and shark protection net programs (pers. comm., Natal Sharks Board (South Africa)). Manta rays, which are caught regularly as by-catch in the Sri Lankan gillnet fishery, are used as shark bait and for human consumption (C. Anderson pers. comm.). There is no further information on bycatch in other fisheries. Incidental catches of manta rays in the protective shark nets off the beaches of KwaZulu-Natal, South Africa, peak from November to February (49% of the total annual manta catch), although the species is caught throughout the year (Young 2001). Mantas rays comprise 16.9% of the total batoid catches from these nets, with a mean annual catch of 60 individuals and an overall 33.7% mortality rate (Young 2001). Unfished populations are not thought to be threatened, however it is not well understood how their use of inshore areas around inhabited coastlines might be affected by anthropogenic influences like pollution, coastal development, and eco-tourism pressures (Tim Clark, unpublished data (Hawaii); Andrea Marshall, unpublished data (Tofo, Mozambique); Bill Acker, pers. comm. (Yap Island); Mocava de Rosemont, pers. comm. (Bora Bora, French Polynesia). The existence of anthropogenic pressures, from direct/indirect fisheries to pollution and exploitation of costal environments, in areas (like Mozambique and Bora Bora, French Polynesia) supporting critical habitats like breeding, birthing, and nursery grounds, is an increased threat to these populations which congregate in mass numbers in these areas or use them as refuges for their young. Increased densities of these individuals during certain seasons, combined with their ease of capture and the lack of regulated fishing management, could result in unsustainable fishing pressure during these times.

Major Threat(s):

Throughout most of their range there are neither directed fisheries for manta rays nor do they make-up large percentages of bycatch in non-target fisheries. However, their large size, slow speed, and tendency to be found on the surface make manta rays an easy target for fishermen. The main threats for this species are fishing activities where mantas are targeted or caught as bycatch. Recent demand for their fins and for their liver and branchial filaments, used in traditional Chinese medicine, has increased fishing activity worldwide for this species.Target fisheries for this species currently exist in several countries, including the Philippines, Mexico, Mozambique, Madagascar, India, Sri Lanka, Brazil, Tanzania and Indonesia (Notarbartolo di Sciara 1987, Alava and Trono 2002, Sea Watch, Portland, Oregon, pers. comm. 1996, H. Dewar, pers. comm., A. Marshall, unpublished data (Mozambique), William White, pers. comm. (Indonesia)).

Traditionally, in many of these areas of South East Asia, Eastern Africa, and Mexico, target fisheries for this species was for local consumption. In Madagascar, Tanzania and Mozambique, mantas were and are occasionally fished in artisanal gillnets and with harpoons. The flesh is primarily used for local consumption (Bianchi 1985, Jiddawi and Stanley 1999, Cooke 2003, Antananarivo 2003, A. Marshall, unpub. data, N. Jiddawi and S. Yahya, Institute of Marine Sciences, (Zanzibar) pers. comm.; and S. Semesi, TRAFFIC – Tanzania, pers. comm.). Isolated reports of fishing for mantas have continued in the Gulf of California. Artisanal pelagic gillnet fishermen throughout the Gulf of California have been observed to retain mantas as bait as well as utilize landed specimens for personal consumption and sale of meat.

Many parts of the manta (skin, liver, fins and dried branchial filaments) are used for local and export trade. The recent increase in the demand for many of these parts has resulted in dramatic increases in fishing pressure for mobulids, including mantas, throughout South East Asia and Eastern Africa, causing a switch from a subsistence fisheries to a commercial export fisheries (Alava and Trono, 2002; A. Marshall, unpublished data (Mozambique)).

In the Pamilacan Island, Philippines, it was reported that approximately 1,000 rays, including the manta ray and a few species of the genus Mobula, were taken between December 1995 and May 1996 by local fishermen using drift nets or harpoon. As a result, fishing was banned in the Philippines in 1998, but this ban was lifted in 1999 due to pressure from fishermen and lack of data on the fishery. During a yearlong survey, from March 2002 to March 2003, 156 manta rays (M. birostris) were caught, mostly in the months from November to January. Since the study, the ban has been re-established for M. birostris. Mantas are now reported to be rare in the Philippines, especially around the Bohol Sea where the fishery was focused. Additionally, Japanese sports divers suggest that the population of manta rays at one site in the Sulu Sea (probably part of the same population fished at Pamilacan Island, Philippines) fell by one half to two-thirds in seven years from the end of the 1980s. (Michiyo Nishitani, pers. comm. 1996). Data from observations in Okinawa Island by T. Itoh, the number of schooling is decreasing from 50 to 30 in 1970s to at most 14 to 15 in 1990s (Homma et al. 1997).

In 2002, the World Wildlife Fund sponsored a trip to the islands of Lamakera and Lamalera in Indonesia to assess the manta ray fishery. Both islands have had traditional subsistence fisheries for manta rays, however Lamakera started fishing for manta rays commercially around 1998. This fishery developed to supply a specific demand from Asia for dried brachial elements, which are used in traditional Chinese medicines. Dewar (2002) estimated traditional catch rates in the village of Lamakera to be 200–300 mantas per year, with catch rates in 2002 estimated at 1,050–2,400 per year. Fishermen indicate that they no longer catch mantas in the traditional areas and are having to travel further to find mantas, and the fishermen on Lamalera caught almost no mantas in 2001, suggesting a substantial decline in the local populations that overlap with the Lamakera fishing grounds.

In Mexico, the species appears to be rare after several decades of fishing. Fishing was banned in Mexico in 2002, when the Mexican government issued Official Rules Regulating Shark and Ray Fisheries in Mexican Waters, making it illegal to capture or kill Manta birostris in Mexican waters. However, the ban was lifted three months after its implementation due to lack of consensus between the different stakeholders, environmental, and tourism sectors. As of 2004, the legislation is still undergoing reviews and changes and has not been enacted, but it still currently provides specific protection for mantas and mobulids in all Mexican waters and prohibits their possession and trade (version 6.2 - Proyecto de Norma Oficial Mexicana Proy-Nom-029-Pesc-2004, pesca responsable de tiburones y rayas. Especificaciones para su aprovechamiento, 2004). Mantas are protected in marine park designated areas within Mexican waters, primarily in the Revillagigedo biosphere, following enforcement of a fishing closure, which began in early 2002.

Even in protected areas such as marine parks and no-catch zones, there is evidence from around the world that targeted fishing still exists for this highly sought after species. In Mexico, enforcement for manta protection has been somewhat suspect as many fishing boats have been observed and caught deploying loglines, gillnets and seines within the Revillagigedo biosphere, which extends as a 12 mile buffer around each of the islands in the archipelago. Mantas have also been targeted in the Komodo Marine Park, very close to Lamakera, despite regulations forbidding fishing. Local dive operators and park rangers report a decline in abundance in the park (H. Dewar, pers. comm.).

Manta rays are also a by-catch in unknown numbers in the tuna purse seine fisheries as well as in other fisheries (Sri Lankan Gill Net Fishery) and shark protection net programs (pers. comm., Natal Sharks Board (South Africa)). Manta rays, which are caught regularly as by-catch in the Sri Lankan gillnet fishery, are used as shark bait and for human consumption (C. Anderson pers. comm.). There is no further information on bycatch in other fisheries. Incidental catches of manta rays in the protective shark nets off the beaches of KwaZulu-Natal, South Africa, peak from November to February (49% of the total annual manta catch), although the species is caught throughout the year (Young 2001). Mantas rays comprise 16.9% of the total batoid catches from these nets, with a mean annual catch of 60 individuals and an overall 33.7% mortality rate (Young 2001).

Unfished populations are not thought to be threatened, however it is not well understood how their use of inshore areas around inhabited coastlines might be affected by anthropogenic influences like pollution, coastal development, and eco-tourism pressures (Tim Clark, unpublished data (Hawaii); Andrea Marshall, unpublished data (Tofo, Mozambique); Bill Acker, pers. comm. (Yap Island); Mocava de Rosemont, pers. comm. (Bora Bora, French Polynesia).

The existence of anthropogenic pressures, from direct/indirect fisheries to pollution and exploitation of costal environments, in areas (like Mozambique and Bora Bora, French Polynesia) supporting critical habitats like breeding, birthing, and nursery grounds, is an increased threat to these populations which congregate in mass numbers in these areas or use them as refuges for their young. Increased densities of these individuals during certain seasons, combined with their ease of capture and the lack of regulated fishing management, could result in unsustainable fishing pressure during these times.

Conservation Actions [top]

Conservation Actions:	Additional research is needed to quantify the extent of target and non-target fisheries take for this species throughout its range. Because of its large size, migratory behavior, extremely low fecundity and large size at maturity, this species is highly vulnerable to fishing pressure. However, life history information is limited, preventing an accurate assessment of the threat posed by fisheries. Elasmobranch catches in most parts of the world generally lack species-specific details. For example, in Mexico, Eastern Africa and parts of South East Asia, many batoids especially eagle rays and smaller devil rays are broadly grouped as “manta rays”. Clearer catch records could help detect potential trends in fishing effort and mortality. Mantas receive protection in some marine protected areas. The Komodo National Park, established in 1980, provides a refuge for manta rays. Mantas are also protected in marine park designated areas within Mexican waters, primarily in the Revillagigedo biosphere, following enforcement of a fishing closure, which began in early 2002. In Hawaii, legislative protection for manta rays from fishing or intentional harm was proposed in 2005 and 2006 through House Bill 960, but the bill is still under review as of 2006. Fishing was banned in the Philippines in 1998 (Camhi et al. 1998), but this ban was lifted in 1999 due to pressure from fishermen and lack of data on the fishery. During a yearlong survey, from March 2002 to March 2003, 156 manta rays (M. birostris) were caught, mostly in the months from November to January. Since the study, the ban has been re-established for M. birostris. Fishing was additionally banned in Mexico in 2002, when the Mexican government issued Official Rules Regulating Shark and Ray Fisheries in Mexican Waters, making it illegal to capture or kill Manta birostris in Mexican waters. However, the ban was lifted three months after its implementation due to lack of consensus between the different stakeholders, environmental, and tourism sectors. As of 2004, the legislation is still undergoing reviews and changes and has not been enacted, but it still currently provides specific protection for mantas and mobulids in all Mexican waters and prohibits their possession and trade (version 6.2 - Proyecto de Norma Oficial Mexicana Proy-Nom-029-Pesc-2004, pesca responsable de tiburones y rayas. Especificaciones para su aprovechamiento, 2004). Even in protected areas such as marine parks and no-catch zones, there is evidence from around the world that targeted fishing still exists for manta rays. In Mexico, enforcement is somewhat suspect, as many fishing boats have been observed/caught deploying longlines, gillnets and seines within the Revillagigedo biosphere, which extends as a 12 mile buffer around each of the islands in the archipelago. Mantas have also been targeted in the Komodo Marine Park, very close to Lamakera, despite regulations forbidding fishing. Local dive operators and park rangers continue to report a decline in abundance in the park (H. Dewar, pers. comm.). There is an extreme paucity of data on this species throughout its range. The limited information from current studies indicate vast differences in the localised ecology and movement patterns of manta rays in different area. As such, much more work is needed on this species to determine life history parameters and fishing pressures in specific populations. In the meantime, a reduction in manta ray landings is essential throughout their range.

Conservation Actions:

Additional research is needed to quantify the extent of target and non-target fisheries take for this species throughout its range. Because of its large size, migratory behavior, extremely low fecundity and large size at maturity, this species is highly vulnerable to fishing pressure. However, life history information is limited, preventing an accurate assessment of the threat posed by fisheries.

Elasmobranch catches in most parts of the world generally lack species-specific details. For example, in Mexico, Eastern Africa and parts of South East Asia, many batoids especially eagle rays and smaller devil rays are broadly grouped as “manta rays”. Clearer catch records could help detect potential trends in fishing effort and mortality.

Mantas receive protection in some marine protected areas. The Komodo National Park, established in 1980, provides a refuge for manta rays. Mantas are also protected in marine park designated areas within Mexican waters, primarily in the Revillagigedo biosphere, following enforcement of a fishing closure, which began in early 2002. In Hawaii, legislative protection for manta rays from fishing or intentional harm was proposed in 2005 and 2006 through House Bill 960, but the bill is still under review as of 2006.

Fishing was banned in the Philippines in 1998 (Camhi et al. 1998), but this ban was lifted in 1999 due to pressure from fishermen and lack of data on the fishery. During a yearlong survey, from March 2002 to March 2003, 156 manta rays (M. birostris) were caught, mostly in the months from November to January. Since the study, the ban has been re-established for M. birostris.

Fishing was additionally banned in Mexico in 2002, when the Mexican government issued Official Rules Regulating Shark and Ray Fisheries in Mexican Waters, making it illegal to capture or kill Manta birostris in Mexican waters. However, the ban was lifted three months after its implementation due to lack of consensus between the different stakeholders, environmental, and tourism sectors. As of 2004, the legislation is still undergoing reviews and changes and has not been enacted, but it still currently provides specific protection for mantas and mobulids in all Mexican waters and prohibits their possession and trade (version 6.2 - Proyecto de Norma Oficial Mexicana Proy-Nom-029-Pesc-2004, pesca responsable de tiburones y rayas. Especificaciones para su aprovechamiento, 2004).

Even in protected areas such as marine parks and no-catch zones, there is evidence from around the world that targeted fishing still exists for manta rays. In Mexico, enforcement is somewhat suspect, as many fishing boats have been observed/caught deploying longlines, gillnets and seines within the Revillagigedo biosphere, which extends as a 12 mile buffer around each of the islands in the archipelago. Mantas have also been targeted in the Komodo Marine Park, very close to Lamakera, despite regulations forbidding fishing. Local dive operators and park rangers continue to report a decline in abundance in the park (H. Dewar, pers. comm.).

There is an extreme paucity of data on this species throughout its range. The limited information from current studies indicate vast differences in the localised ecology and movement patterns of manta rays in different area. As such, much more work is needed on this species to determine life history parameters and fishing pressures in specific populations. In the meantime, a reduction in manta ray landings is essential throughout their range.

Citation:	Marshall, A., Ishihara, H., Dudley, S.F.J., Clark, T.B., Jorgensen, S., Smith, W.D. & Bizzarro, J.J. 2006. Manta birostris. In: IUCN 2008. 2008 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Downloaded on 23 April 2009.
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