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Habitat segregation and mosaic sympatry of
the two species of manta ray in the Indian
and Pacific Oceans: Manta alfredi and
M. birostris
tom kashiwagi
, andrea d. marshall
, michael b. bennett
and jennifer r. ovenden
School of Biomedical Sciences, University of Queensland, St Lucia, QLD 4072, Australia,
Molecular Fisheries Laboratory,
Queensland Government, PO BOX 6097, St Lucia, QLD 4072, Australia,
Manta Ray & Whale Shark Research Center, Tofo Beach,
Inhambane, Mozambique
Habitat use of Manta alfredi and M. birostris was assessed at 20 localities in the Indian and Pacific Oceans based upon 3328
photographic observations. Geographical relationships of the two species were scored as either microallopatry, microparapatry
or microsympatry at each locality. Our study revealed a mosaic habitat occupancy by the two species within their macrosym-
patric range.
Keywords: Chondrichthyes, Manta alfredi,Manta birostris, sympatry, parapatry, allopatry, migration
Submitted 16 December 2010; accepted 14 March 2011
Recent taxonomic revision within the Mobulidae (devilrays)
has divided the previously monotypic genus Manta into two
species (Marshall et al., 2009), the reef manta ray Manta
alfredi (Krefft, 1868) and the giant manta ray M. birostris
(Walbaum, 1792). The distribution of the species is circum-
global for M. birostris and semi-circumglobal (absent in the
East Pacific and West Atlantic Oceans) for M. alfredi, which
suggests large-scale macrosympatry (i.e. overlapping geo-
graphical ranges, defined by Smith (1965)). The two species
are distinguishable by external coloration on their dorsal
and ventral body surfaces (Marshall et al., 2009). Relatively
rare melanistic (black) and leucistic (white) colour morphs
exist in both species, with the distinguishing coloration
pattern still often visible. The pattern of coloration in M. bir-
ostris is fairly constant worldwide but that of M. alfredi varies
considerably. Manta alfredi is a more tropical, coastal, resi-
dential, smaller (maximum disc width, W
, of about 5 m)
and schooling species compared to M. birostris, and is
found around coral and rocky reefs, tropical island groups
and atolls. Manta birostris is a more cold-water tolerant,
pelagic, migratory, larger (maximum W
of about 7 m) and
solitary species, which is commonly sighted at offshore pinna-
cles, seamounts and oceanic islands (Marshall et al., 2009).
While the scientific literature on manta ray biology and life
history is relatively sparse, several points on inter-specific
similarities can be made. Individuals of both species demon-
strate a sophisticated ability to sample and choose habitat.
For example, both species demonstrate habitat fidelity and
seasonal aggregation behaviours (Dewar et al., 2008; Luiz
et al., 2009; Marshall, 2009). They both visit specific sites,
such as ‘cleaning stations’: patches of reef where various
‘cleaner’ fish species remove parasites from their body, and
‘feeding areas’: locations where dense plankton blooms com-
monly occur (Homma et al., 1999; Marshall, 2009;
Anderson et al., 2011a, b). Both species travel at least
meso-scale distances, with movements between locations up
to 500 km apart recorded for M. alfredi in Japanese and
Australian waters (Kashiwagi et al., 2010; Couturier et al.,in
press) and over 1000 km for M. birostris (Marshall et al.,
2010). The two species show similar courtship and mating
behaviours (Yano et al., 1999; Marshall & Bennett, 2010).
Both species are slow to mature (10 years for females) and
have low fecundity (with mostly a single offspring every 2 to
3 years or possibly longer cycles on average), based on
decades-long observation of a population of M. alfredi in
Japan since the mid-1970s (Ito, 1987, 2000) and similar
reports by other authors (Homma et al., 1999; White et al.,
2006; Marshall, 2009; Marshall & Bennett, 2010).
The considerable similarities in the biology of the two
species and their macrosympatric distribution raise the ques-
tion of whether habitat use is segregated between M. alfredi
and M. birostris. It is important to study microgeographic
relationships in their ranges to understand differences in
habitat preferences and habits that could have been important
in their evolutionary history (Mayr, 1942, 1947, 1963; Rivas,
1964; Smith, 1965). While a map depicting worldwide, macro-
sympatric distribution of the two species has been presented
previously (Marshall et al., 2009), the purpose of the current
paper is to elucidate habitat segregation at a microgeographic
scale at various localities by increased effort in collecting and
analysing photographic records. Photo-identification of
Corresponding author:
T. Kashiwagi
Marine Biodiversity Records, page 1 of 8. #Marine Biological Association of the United Kingdom, 2011
doi:10.1017/S1755267211000479; Vol. 4; e53; 2011 Published online
individual manta rays emerged in the 1970s (Ito, 1987) and is
now employed successfully in many locations around the globe
(Ishihara & Homma, 1995; Clark, 2002; Marshall, 2009;
Deakos, 2010; Kitchen-Wheeler, 2010; Couturier et al.,in
press; Marshall et al., in press). Manta rays are major photo-
graphic subjects for SCUBA divers and it is common for
images of manta rays to be uploaded in the internet environ-
ment as newsworthy material that can be found by keyword
searches. These ‘manta ray occurrence data’ with supporting
photographic images and location information have become
highly accessible due to recent expansion in digital communi-
cation (e.g. web page of dive operations, blogs, YouTube http:// and Facebook,
even from places where occurrences are rare. With a reason-
able search effort, these data can provide a robust record of
the occurrence of manta ray at specific sites, together with
an indication of the frequency of site visitation (Kashiwagi
et al., 2010). This unique situation makes the current study
feasible. This paper utilizes photographic records from mul-
tiple sources to establish baseline distributional data on a
global geographical scale. These data will assist future moni-
toring and assessment of responses of these two species to
possible changes in the marine environment (Soberon &
Peterson, 2009; Boakes et al., 2010) as well as considering evol-
utionary hypotheses.
The geographical relationships of populations of the two
species at 20 localities in the Indo-Pacific Ocean, using a
total of 3328 photographic records, was assessed. The charac-
terization of the geographical relationships of two or more
species in a unit area is dependent on scales, that is, the resol-
ution at which patterns are observed. Although numerous
terms and concepts for characterizations and demarcations
exist (e.g. reviewed by Mayr (1942) and Rivas (1964)), we
used the ones proposed by Smith (1965) here. Under macro-
sympatry, Smith (1965) proposed ‘microsympatry’, ‘microal-
lopatry’ and ‘microparapatry’. For the purpose of this paper,
we scored the geographical relationships exhibited at a locality
by the two species as either ‘microallopatry’ (record of
co-occurrence at distances less than 100 km apart was not
observed), ‘microparapatry’ (record of co-occurrence within
2 100 km was observed, but no record of co-occurrence at
the same dive site, typically defined by a 100 m radius, was
observed) or ‘microsympatry’ (record of co-occurrence at
the same dive site was observed). We used these terms on
the basis of occurrence records only and did not consider
other ecological phenomena that could be associated with
these terms (e.g. physical or reproductive contact).
Reflecting the above resolution, we collated our data with
detailed site information within localities where the two
species occurred. There were up to 15 sites per locality. For
localities where only one species occurred, the site information
was represented with a few main sites (up to 4 sites per
locality). Names of the 20 localities, 91 sites, their latitude
and longitude and a total number of individuals per locality
identified in this study are listed in the Appendix.
More than 80% of those observed records were from long-
term photo-identification projects conducted by the authors
and our field collaborators that utilize spot patterns on the
ventral surface for individual identification purposes. To be
consistent with a given total number of individuals per locality,
individuals photographed at multiple sites were counted as one
record at one representative site only. Other sources of records
included private collections, museum records, magazine
articles and web-based information (e.g. web-based manta
ray identification databases, catalogued stock photograph
entries, tour reports and other web pages). Examples of web-
based manta ray identification databases include: Manta
Pacific Research Foundation (
mantapacific/) and Manta Conservation Thailand
Identification Group in Facebook (
For web-based searches, we spent at least six hours of targeted
keyword searches for each locality, which found many
records from localities where sighting records were abundant
and a small number of records from localities where sighting
records were relatively scarce. Authenticity of the record was
checked by contacting the photographer for confirmation
where needed (e.g. rare occurrence of the species at the
location). Further we interviewed people with local knowledge
to seek clarification about whether any apparent scarcity of
web-based records was a realistic representation of the sighting
frequency of manta rays at those locations. These people were
able to provide additional information about the frequency
of occurrence and habitat utilization of two species at the
Species identification was based on the differences in color-
ation patterns described in character keys of Marshall et al.
(2009). We also recognized keys provided in Sato et al.
(2010), however, we found that their keys, which were con-
structed based on very small sample sizes, were not useful
for identification due to the inaccurate and insufficient
descriptions of coloration patterns for the two species.
Microsympatry and microparapatry
Across the examined twenty localities in the Indian and
Pacific Oceans (Figure 1 & Appendix), we found occurrences
of both species at eight localities. In general, sites (within
localities) of occurrences appeared to be segregated between
the two species. However, most localities included a few to
several sites where the two species occurred in microsympatry.
Mozambique was the only locality where both species
occurred in microsympatry along a wide range of coastline.
At this locality, several microsympatric sites were identified
where both species occurred regularly and were recorded in
large numbers. The two species occurred in microsympatry at
over 15 feeding sites and cleaning sites from Office Reef
(23842S35834E) in the north off Inhambane to Zavora
(24828S35814E) in the south. While the two species some-
times can be seen in a single dive, the two species do not interact
with each other. For example, the two species feeding in a group
or females being chased by allo-specific males, was not
observed. There were a large number of records in this locality
(N ¼760). The majority of the records were for Manta alfredi
The northern Red Sea was previously known as a habitat of
M. birostris from records around Sharm el Sheikh, Egypt
(2880N34828E–27847N34815E), Brother Islands
(26819N34851E) and St John’s Reef (23827N35852E)
(Marshall et al., 2009). Our study found occurrence records
2tomkashiwagiet al.
of M. alfredi in shallow habitat west of the Sinai Peninsula
around Sha’ab el Erg (27823N33852E) as well as from a
site in Sharm el Sheikh (27853N34819E). We did not find
M. birostris around Sha’ab el Erg, and records of M. alfredi
around Sharm el Sheikh were very rare. There were no indi-
cations of regular co-occurrence of the two species around
Sharm el Sheikh (Helen Chambers, Catherine Bates and
Tina Gauer, personal communications). Both species occurred
in Sudanese waters with records of M. alfredi at Mesharifa
(20853N37813E) and records of M. birostris at Sha’ab
Rumi (19856N37824E) and Angarosh (20854N37812E).
In the Maldives, both species occurred around the atoll of
Addu (0836S7389E), North Male
´(4816N73833E) and Baa
(5810N7388E). However, the vast majority of the photo-
graphic records were for M. alfredi (95%). There were no
indications of regular co-occurrence of the two species at
the same sites. Our interview with a local observer (Guy
Stevens, personal communication) noted that M. birostris
tended to occur along outer atoll edges where the reef drops
off steeply into extremely deep water, but he reported that
sightings were certainly not consistent in most locations and
could also occur randomly inside the atolls. The overall rare-
ness of M. birostris was also reported in Kitchen-Wheeler
(2010), which identified over 1000 individuals.
In Western Australia, both species occurred around
Bateman Bay. There was a large number of records of M.
alfredi (N ¼540) at inner reef sites (2387S 113845E), but
no observation of M. birostris. Both species occurred at sites
in the outer reef zone (2386S 113843E), that were infre-
quently visited by divers. Our interview with a local observer
(Frazer McGregor, personal communication) noted that this
zone was utilized by M. alfredi as a pathway to inner reef
sites as well as feeding and cleaning year-around. He reported
that sightings of M. birostris were rare and that there were no
known cleaning stations for this species.
In Indonesia, Raja Ampat (288S 130850E) was known to
be a habitat of M. alfredi (Marshall et al., 2009) but this
study found that M. birostris appeared from time to time
from (Shawn Henrichs, personal communication). Similarly,
both species occurred around Komodo (8844S 119824E).
Images from around Bali (8846S 115829E) and Sangalaki
(285N 118823E) indicated the presence of M. alfredi, while
M. birostris occurred in the Alas Strait (8829S 116845E)
and at Anambas (384N 105840E).
In the Philippines, M. alfredi was found in the reefs of Apo
(12839N 120825E), Basterra (884N 119818E), Tubbataha
(8852N 119854E) and around Ticao Island (12841N
123842E), while M. birostris was found around Puerto
Princesa Bay (9842N 118845E) and around Malapascua
Island (11818N 124811E). We could find only a relatively
small number of photographic records from this locality
(N ¼20) despite a presumed abundance of SCUBA diving
activities and abundance of manta rays reported in the past
(Alava et al., 2002).
The Ryukyu Arc region in Japan was previously known as a
habitat of Manta alfredi based on records of this species from
the year-round aggregation site around Ishigaki Island
(24829N 12487E) and seasonal occurrence around Miyako
Islands (24849N 12587E) (Marshall et al., 2009). The occur-
rence of both species around Yonaguni Island (24826N
122855E) and around Okinawa Honto (26818N 127844E)
was reported recently (Kashiwagi et al., 2010). This study dis-
covered the occurrence of M. birostris at Miyako Islands
(24849N 12587E) and an offshore site in the East China
Sea (29858N 126854E, National Museum of Nature and
Science, Tokyo: NSMT-P 63289). The record of the offshore
site was from a trawl survey by the fisheries agency and this
record highlights the possibility that the surveys outside the
area of normal SCUBA diving activities might reveal unrec-
orded occurrences of M. birostris in various localities. The
records of the occurrence around Okierabu (27850N
128837E), Tokunoshima (27847N 128853E, 27850N
128858E) and Amamiooshima (28830N 129843E) were
rare (Kiyohisa Kawamoto, Shoji Ito and Masahiro
Yoshikawa, personal communication) and records were of
M. alfredi only. There was a reasonable amount of SCUBA
diving activity around these three islands and we would
have expected to find more records if manta rays are abun-
dant. Overall, the majority of the records in the Ryukyu Arc
were M. alfredi (99%).
In Hawaii, records from around Ukumehame, Maui
(20847N 156835W), Ho’ona Bay, Hawaii (19844N
15683W), and Keauhou, Hawaii (19833N 155857W) were
of M. alfredi. Two offshore sites, Three Room Cave, Hawaii
Fig. 1. Habitat use by Manta alfredi and M. birostris.W&*, indicate ‘microallopatry’ (see main text for definition) by M. alfredi and M. birostris, respectively. A
half and half black and white circle indicates the occurrence of both species either in ‘microparapatry’ or ‘microsympatry’. See main text for details. Locality codes
(a – t) correspond to those in the Appendix: a, Mozambique; b, Egypt and Sudan; c, Maldives; d, Thailand; e, Cocos Keeling, Australia; f, Christmas Island,
Australia; g, Western Australia; h, eastern Australia; i, Indonesia; j, Philippines; k, Micronesia and Palau; l, Guam, USA; m, Ryukyu Arc, Japan; n, Ogasawara,
Japan; o, New Zealand; p, Hawaii; q, Kiribati; r, French Polynesia; s, Revillagigedo Islands, Mexico and Clipperton Island (Fr); t, Costa Rica, Colombia and Ecuador.
mosaic sympatry of manta alfredi and m. birostris 3
(19829N 15682W) and Paradise Pinnacle, Hawaii (19826N
15680W) and a nearshore site Kaiwi Point (19839N
15682W) had records of M. birostris only. Both species
occurred in microsympatry at Molokini, Maui (20838N
156829W), Honokohau Harbor, Hawaii (19840N 15681W)
and Keauhau offshore (19833N 155858W). Some local
divers have been calling M. birostris ‘pelagic manta’ which
tended to occur at offshore dive sites and they have long
recognized the differences between it and M. alfredi, which
occurs at popular near-shore night diving sites (Manta
Pacific Research Foundation
mantapacific/). Overall, the majority of records from Hawaii
were for M. alfredi (95% in Maui and 80% in Hawaii).
In Cocos Keeling, Australia, only M. alfredi was found (N ¼
2). Compared with other localities in this study, the amount
of SCUBA diving activities in this locality is relatively low.
Thus, more information is necessary.
In eastern Australia, only M. alfredi was found in large
numbers (N ¼364) from three sites, Lady Elliot Island
(2486S 152842E), North Stradbroke Island (27825S
153833E) and Byron Bay (28836S 153837E). There have
been no confirmed photographic records of M. birostris
from this locality, despite considerable amount of effort in
gathering records (Couturier et al., in press). This indicated
that M. birostris is at least not abundant where SCUBA
diving activities were taking place.
Similarly, only M. alfredi was found in other localities,
Micronesia and Palau (9834N 138811E, 6859N 158817E,
787N 134816E and 7838134833E), Guam, USA (13830N
144847E, 13827N 144837E and 13826N 144836E), Kiribati
(1856N 157828W) and Bora Bora, French Polynesia
(16829S 151842W), where the amount of SCUBA diving
activities were relatively high. There have been no confirmed
photographic records of M. birostris from French Polynesia,
despite considerable effort in gathering records (Moeava de
Rosemont, personal communication).
Only M. birostris was found around Thailand (8849N
97846E, 8840N97838E and 789N98849E), Christmas
Island, Australia (10825S 105838E), Ogasawara Islands,
Japan (2782N 142814E and 26840N 142810E), and New
Zealand (35827S 174844E).
Only M. birostris was found among a large number of
records collected from Revillagigedo Islands, Mexico and
Clipperton Island (Fr) (19818N 110849W and 10819N
109812W), and Costa Rica, Colombia and Ecuador (5833N
8785W, 480N81836W, 0824S90819W and 1815S
8183W). The absence of M. alfredi in the East Pacific Ocean
was previously reported (Marshall et al., 2009) and this
study supported this with a larger number of observations.
Habitat segregation and mosaic sympatry
Our study revealed mosaic habitat occupancy between the
closely-related species Manta alfredi and M. birostris in the
majority of their distributional range. At twelve localities,
they were microallopatric, while at eight localities they were
microparapatric interspersed with mostly only a few micro-
sympatric sites. Given the known mobility of both species,
this pattern suggests that two species have distinct habitat
use and habitat preference. Physical and biotic factors
influencing habitat selection is an important but relatively
neglected area of research in biology of sharks and rays until
recently (Simpfendorfer & Heupel, 2004). In addition,
patchy, interdigitated distribution of the two forms in sympa-
try is sometimes termed as ‘mosaic sympatry’ (Mallet, 2008;
Mallet et al., 2009) and distinguished from a more universally
mixed pattern, ‘pure sympatry’. This has important impli-
cations in considering how ecological adaptation might have
played a role in the evolution of the two species.
Habitat segregation between M. alfredi and M. birostris has
been suggested between near-shore and offshore environ-
ments, respectively (Marshall et al., 2009). Our study sup-
ported this generally, finding that M. alfredi commonly uses
shallow near-shore environments while M. birostris commonly
occurs on offshore reefs, islands or locations that are in close
proximity to deep water, such as the edge of the continental
shelf. For example, in localities where the two species are
known to co-occur, M. birostris is often reported from offshore
reefs (e.g. St John’s Reef in the Red Sea; offshore dive sites in
Hawaii Island and Western Australia), offshore islands (e.g.
the Brother Islands in the Red Sea), the extremities of island
groups (e.g. Addu Atoll in the Maldives) or outer atoll edges
near drop-offs (e.g. Addu, North Male
´, and Baa Atolls in the
Maldives). Microallopatry of M. alfredi was recorded from
shallow reef environments in Yap, Pohnpei, Palau, eastern
Australia and French Polynesia, while microallopatry of
M. birostris (e.g. Ogasawara, Japan; New Zealand; Thailand
and all East Pacific localities in this study) was recorded
from habitats characterized by a more oceanic environment.
The relationship between occurrence of each species and
physical variables such as distance from land or proximity
to the deep water is likely to be complex. Microgeographic
relationships between the two species are likely to be further
complicated by more precise habitat choice and the migratory
behaviour of both species, causing labile boundaries.
Examples of distributions that are beyond the simple expla-
nation of near-shore or offshore partitioning include the
intermingled habitat occupancy observed in some localities
(e.g. Indonesia and Philippines). Seasonal shifts in Manta
spp. distributions or seasonal change in visitation patterns
(Duffy & Abbot, 2003; Dewar et al., 2008; Anderson et al.,
2011a, b; Couturier et al., in press) may accompany changes
in microgeographic relationships between the two species in
locations where both species occur.
The precise nature of physical and biotic factors that
characterize the observed habitat segregation between the
two Manta spp. is still uncertain and deserves further
focused research. This will enhance understanding of the eco-
logical requirement of the two species and contribute to a
better management of their populations. We hypothesize
possible niche divergence in physical dimensions such as
water temperature, depth, light regime and spatial and tem-
poral characteristics of upwelling events. Biotic dimensions
might include primary production, availability of suitable
food (zooplankton), contrasting parasite communities, con-
trasting cleaner fish communities and risk of predation by
sharks. These are in line with several mechanisms suggested
by Bull (1991) in the studies of the ecology of parapatric dis-
tribution, which includes: (1) ecotonal change; (2) inter-
specific competition preventing species from invading each
other’s habitat; (3) differences in susceptibility to predation;
(4) contrasting interaction with parasites and disease; and
(5) reproductive interference.
4tomkashiwagiet al.
The evolutionary origin of the two species is also of interest.
Preliminary studies suggested that the genetic distance between
the two species is not so large and speciation might be recent
(Kashiwagi, unpublished data). Consideration of how the
observed pattern of mosaic sympatry arose along with specia-
tion scenarios is a subject of our ongoing study.
We thank the people listed in the Appendix footnotes and Dr
Gento Shinohara (National Museum of Nature and Science,
Tokyo) for providing photographic records. We appreciate
the support provided by Sea World Research & Rescue
Foundation, Australian Biological Resource Study, the Save
Our Seas Foundation, the Queensland Government and the
University of Queensland. We wish to thank Gimme
Walter, James Hereward, Andrew Ridley, Jason Callander,
Michelle Rafter, Iman Lissone and two anonymous referees
for their helpful comments and suggestions.
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southern Mozambique. PhD thesis. The University of Queensland,
St Lucia, Queensland, Australia.
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Kitadani Y. and Miura H. (2010) Records of manta ray
(Myliobatidae) from southern Japanese waters and their taxonomy,
mosaic sympatry of manta alfredi and m. birostris 5
field identifications and suggested Japanese names. Report of Japanese
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Correspondence should be addressed to:
T. Kashiwagi
Molecular Fisheries Laboratory
Queensland Government
PO BOX 6097, St Lucia
QLD 4072, Australia
Appendix Details of photographic records of Manta alfredi and M. birostris. Names of localites, sites, latitude and longtitude and the number of observed
individuals (N) are listed. Sources are indicated as private collections (P); web-based information (W); magazine articles (M); museum records (Mus.);
and published references (numbers). See footnotes for more information.
Locality/site Latitude and longitude Total N Manta alfredi Manta birostris Sources
a. MOZAMBIQUE 760 P, 1, 2
Office Reef (23842S35834E) 100 20
Barra Point (23846S35832E) 20 5
Giant’s Castle (23850S35833E) 100 20
Salon (23849S35832E) 20 5
Rob’s Bottom (23858S35831E) 30 5
Manta Reef (23858S35831E) 105 30
XTC (24800S35831E) 100 25
Paindane (24805S35830E) 30 3
Island Rock (24809S35829E) 20 2
Zavora (RS) (24828S35814E) 100 20
b. EGYPT and SUDAN 42 P, W
Jacksons Reef (28800N34828E) – 1
Near Garden (27854N34820E) – 2
Tower, Sharm el-Sheikh (27853N34819E) 1 1
Pinky Wall (27851N34819E) – 1
Paradise (27850N34819E) – 4
Ras Umm Sid (27850N34818E) – 3
Temple, Sharm el-Sheikh (27850N34818E) – 2
Ras Katy (27850N34818E) – 1
Ras Ghozlani (27847N34815E) – 3
Sha’ab el Erg (27823N33852E) 4 –
Brother Island (26819N34851E) – 8
St John’s Reef (23827N35852E) – 6
Mesharifa (20853N37813E) 3 –
Angarosh (20854N37812E) – 1
Sha’ab Rumi (19856N37824E) – 1
c. MALDIVES 100 P, W
Baa Atoll (05810N73808E) 68 2
Addu Atoll (00836S73809E) 2 3
North Male
´Atoll (04816N73833E) 23 2
Ko Bon (08849N97846E) – 30
Similan Islands (08840N97838E) – 15
Hin Daeng (07809N98849E) – 30
Cocos Keeling (11843S96845E) 2 –
Christmas Island (10825S 105838E) – 6
6tomkashiwagiet al.
Appendix Continued
Locality/site Latitude and longitude Total N Manta alfredi Manta birostris Sources
Bateman Bay (23807S 113845E) 540 –
Bateman Bay offshore (23806S 113843E) 10 1
Lady Elliot Island (24806S 152842E) 306 –
North Stradbroke Island (27825S 153833E) 47 –
Byron Bay (28836S 153837E) 11 –
i. INDONESIA 136 P, W, M, 4
Raja Ampat (02808S 130850E) 23 2
Sangalaki (02805N 118823E) 30 –
Bali (08846S 115829E) 25 –
Anambas (03804N 105840E) – 1
Komodo (08844S 119824E) 23 2
Alas Strait (08829S 116845E) – 30
Apo Reef (12839N 120825E) 3 –
Basterra Reef (08804N 119818E) 3 –
Tubbataha Reef (08852N 119854E) 3 –
Ticao Island (12841N 123842E) 5 –
Malapascua Island (11818N 124811E) – 5
Puerto Princesa Bay (09842N 118845E) – 1
Yap (09834N 138811E) 100 –
Pohnpei (06859N 158817E) 10 –
Palau, German Channel (07807N 134816E) 15 –
Palau, Yuukaku Channel (07838N 134833E) 5 –
l. GUAM, USA 6 W
Tumon Bay (13830N 144847E) 4 –
Apra Harbor (13827N 144837E) 1 –
Blue Hole (13826N 144836E) 1 –
m. RYUKYU ARC, JAPAN 373 P, W, Mus.,
Kubura Harbor, Yonaguni (24827N 122856E) 1 5, 6, 7, 8,
Nishizaki, Yonaguni (24826N 122855E) 1 9, 10
Ishizaki, Ishigaki Island (24829N 124807E) 292 –
Irabu, Miyako Islands (24849N 125807E) 50 1
East China Sea (29858N 126854E) – 1
Kuroshima (26814N 127824E) 15 –
Chatan, Okinawa Honto (26818N 127844E) 1∗∗
Yomitan, Okinawa Honto (26823N 127843E) 5 (1)∗∗∗
Ishikawa, Okinawa Honto (26815N 127850E) – 1
Kanna, Okinawa Honto (26827N 127857E) 1 –
Nagasakibana, Okierabu (27820N 128837E) 1 –
Senma, Tokunoshima (27847N 128853E) 1 –
Misaki Prince Beach, Tokunoshima (27850N 128858E) 1 –
Nanatsuse, Amamiooshima (28830N 129843E) 1 –
Chichijima (27802N 142814E) 24 –
Hahajima (26840N 142810E) 28 –
o. NEW ZEALAND 17 P, W, 11
Poor Knights Islands (35827S 174844E) – 17
p. HAWAII 214 W
Molokini (20838N 156829W) 10 4
Ukumehame, Maui (20847N 156835W) 72 –
Ho’ona Bay, Hawaii (19844N 156803W) 60 –
Honokohau Harbor, Hawaii (19840N 156801W) 4 2
Kaiwi Point, Hawaii (19839N 156802W) – 2
Keauhou, Hawaii (19833N 155857W) 52 –
Keauhou offshore, Hawaii (19833N 155858W) 2 2
Three Room Cave, Hawaii (19829N 156802W) – 2
Paradise Pinnacle, Hawaii (19826N 156800W) – 2
mosaic sympatry of manta alfredi and m. birostris 7
Appendix Continued
Locality/site Latitude and longitude Total N Manta alfredi Manta birostris Sources
Kiribati (01856N 157828W) 20 –
Bora Bora (16829S 151842W) 85 –
60 P, W
Isla San Bebedicto, Mexico (19818N 110849W) – 57
Clipperton Island (Fr) (10819N 109812W) – 3
Isla del Coco, Costa Rica (05833N87805W) – 5
Galapagos Islands, Ecuador (00824S90819W) – 15
Isla La Plata, Ecuador (01815S81803W) – 300
Malpelo Island, Colombia (04800N81836W) – 5
, Private collections were provided by: Andrea Marshall (a, b, c, i, k, s, t); Simon Pierce (a); Helen Chambers (b); Robert Fabbri (b); Tina Gauer (b);
Rudolf Svensen (b); Guy Stevens (c); Ken Hoppen (f); Frazer McGregor (g); Christine Dudgeon (h); Mark Atkinson (h); Kathy Townsend (h); Lydie
Couturier (h); Tom Kashiwagi (i); William White (i); Jenny Giles (i); Shawn Heinrichs (i); Edi Frommenwiler (i); Tim Rock (a, k); Bill Acker (k);
Mark Thorpe (k); Tova Harel-Bornovski (k); Takashi Ito (k, m); Shoji Ito (m), Masahiro Yoshikawa (m), Yuki Toyozato (m), Kazunari Yano (m)
Kiyohisa Kawamoto (m), Yoshihisa Hagiwara (m); Fumihiko Sato (n); Clinton Duffy (o); Tim Dykman (q); Moeava de Rosemont (r); Tom
Campbell (a, s, t); Terry Mass (s); and Mark Harding (t). Published references are: 1, Marshall (2009); 2, Marshall et al. (in press); 3, Couturier et al.
(in press); 4, White et al. (2006); 5, Ito (1987); 6, Ito (2000); 7, Uchida (1994); 8, Masuda et al. (1984); 9, Kashiwagi et al. (2010); 10, Sato et al.
(2010); 11, Duffy & Abbot (2003); and 12, de Rosemont (2010). A list of URLs for web-based information, magazine titles, issue numbers, page
numbers and photograph credits is available from the corresponding author. ∗∗, site and identification based on the account of Uchida (1994) and
the photograph in Masuda et al. (1984); ∗∗∗, identification according to Sato et al. (2010). No photograph of this individual in the cited paper.
8tomkashiwagiet al.
... The zooplanktivorous reef and oceanic manta rays (Mobula alfredi and M. birostris, respectively) are two of the ocean's largest species (Marshall et al., 2009;White et al., 2018). Fragmented populations of M. alfredi are widely distributed throughout the tropical and sub-tropical waters of the Indo-West Pacific Oceans, where they frequent coastal reef habitats, but also use offshore environments and the mesopelagic zone (Kashiwagi et al., 2011;Couturier et al., 2012;Braun et al., 2014;Jaine et al., 2014;Stevens et al., 2018a;Hosegood, 2020). Mobula birostris are distributed throughout all tropical oceans and also range into temperate waters. ...
... Mobula birostris are distributed throughout all tropical oceans and also range into temperate waters. They are more oceanic in habitat use than M. alfredi, visiting shallow coastal areas infrequently (Kashiwagi et al., 2011;Couturier et al., 2012;Stewart et al., 2016a;Stevens et al., 2018a). Both species demonstrate long-term site fidelity, and form seasonal aggregations at key habitats (Dewar et al., 2008;Jaine et al., 2012;Braun et al., 2015;Stewart et al., 2016bStewart et al., , 2018aCouturier et al., 2018;Setyawan et al., 2018;Germanov et al., 2019;Perryman et al., 2019;Harris et al., 2020;Pate and Marshall, 2020). ...
... Mobula birostris are less frequently sighted, except during a few months each year (March-April) at Addu and Fuvahmulah, the two southernmost atolls of the archipelago (Stevens, 2016;Maldvian Manta Ray Project [MMRP], 2019a;Nicholson-Jack et al., 2021). These areas are close to deep-water oceanic habitat (Stevens, 2016), where M. birostris are most commonly encountered throughout their range (Kashiwagi et al., 2011;Stewart et al., 2016a). In the Maldives, individual M. birostris are rarely re-sighted, which suggests the population is transient, and predominantly uses habitat away from the reef systems there (Maldvian Manta Ray Project [MMRP], 2019a). ...
Full-text available
Manta ray populations worldwide are vulnerable to sublethal injuries resulting from human activities, e.g., entanglement in fishing line and boat strikes, which have the potential to impact an individual’s health, fitness, and behaviour. Sublethal injuries and physical abnormalities also occur naturally from predation events, deformity, parasites, and disease. To determine the type and frequency of anthropogenic and natural originated injury events affecting Mobula alfredi and M. birostris in the Maldives, we examined data from the Manta Trust’s Maldivian Manta Ray Project (MMRP) database, which contains 73,638 photo-identification (photo-ID) sightings of the two manta ray species from 1987 to 2019. The likely origin of each injury or physical abnormality was determined based on visual assessment of the photo-ID images. Multiple injuries to an individual originating from the same event were grouped for analysis. Generalised linear mixed models (GLMM) were used to investigate the relationship between the occurrence of injury events and the explanatory variables sex and maturity status for both species, with the additional variable site function (cleaning, feeding, cruising) investigated for M. alfredi. Spatial and temporal variations in M. alfredi injury events, and their origin and type, were investigated by calculating the percentage of injury events per sighted individual at each Maldivian atoll, and per re-sighted individual in each year from 2005 to 2019. For both species, injury events were predominantly of natural origin, with predatory bites being the most frequent type. The most common anthropogenic injury type was entanglement in fishing line. Injuries to M. alfredi were significantly more likely to be observed on juveniles than adults, males than females, and at cleaning stations as opposed to feeding or cruising sites. Neither sex nor maturity status were significant explanatory variables for the occurrence of injuries to M. birostris. Highest percentages of anthropogenic injuries per sighted M. alfredi were recorded in North Malé, South Malé, Baa, Addu, and Laamu Atolls, where boat traffic, fishing, and tourism activities are concentrated. Overall, this work greatly improves understanding of the sublethal threats faced by manta rays in the Maldives; identifying focus areas where conservation management actions are required to ensure more effective protection of this threatened species group.
... To identify the influences of small-scale (10s km) habitat use which occur at three key habitats (Hanifaru Bay, Nelivaru Thila and Dhigu Thila) during the SW Monsoon (when they are predominantly utilised by M. alfredi [7]), all detection data from the SW Monsoon months (1) and absent (0) was established for each hour; from five hours before the first detection until five hours after the last detection during the period while acoustic receivers were recording ( Table 2). The final time-series for each location included the following number of presence and absence observations: Hanifaru Bay = 13335, Dhigu Thila = 12971, and Nelivaru Thila = 13470. ...
... Trees were built with recommended parameters to ensure model outputs were comparable among locations [45]: tc of 5, lr of 0.05, bf of 0.5 and ss of 50 [49]. All combinations of parameters tc (1,2,3,4,5), lr (0.01, 0.005, 0.001 and 0.0001), bf (0.5, 0.7, 0.9) and ss (25,50) [45,50] were also tested, but provided minimal improvement in model performance. ...
Full-text available
A detailed understanding of the dynamics of small-scale (10s km) habitat use by the reef manta ray (Mobula alfredi) in the Maldives Archipelago is required to develop an effective national conservation management plan for this wide-ranging species. Here, a combination of photo-ID sightings data and acoustic telemetry were used to investigate both long-term M. alfredi visitation trends and small-scale movement patterns to key habitats on the eastern side of Baa Atoll (Hanifaru Bay feeding area, Dhigu Thila multifunctional site, and Nelivaru Thila cleaning station). All tagged and most of the sighted M. alfredi exhibited high affinity to the eastern side of Baa Atoll, where 99% of detections occurred, and 69% of individuals were re-sighted in multiple years. Sightings data suggests that visitation patterns may be associated with differences in habitat use by sex and maturity status. Boosted regression trees indicated that tag detection probability at Hanifaru Bay increased with increased westerly wind speed (>5ms-1) during the day, close to a new and full moon just after high tide, and when the tidal range was low. Interaction effects between predictors suggest that wind-driven oceanographic processes, such as Langmuir Circulation, maybe working to increase zooplankton concentration at this location. Tag detection probability increased at Dhigu Thila under similar conditions. At Nelivaru Thila, it increased at lower wind speeds (
... The unique and stable ventral markings of individual rays have facilitated photo-identification (photo-ID) studies at these aggregation sites, providing the foundation for manta ray research in many locations across the globe (e.g., Couturier et al., 2014;Deakos et al., 2011;Germanov et al., 2019;Harris et al., 2020;Homma et al., 1999;Kumli & Rubin, 2008;Marshall et al., 2011;Stevens, 2016). This technique has been used to assess home range (Deakos et al., 2011;Kashiwagi et al., 2011), longevity (Clark, 2010;Couturier et al., 2014;Kashiwagi, 2014;Rubin, 2002), migration patterns (Armstrong et al., 2019;Germanov & Marshall, 2014), site affinity (Couturier et al., 2011;Germanov et al., 2019;Marshall et al., 2011), reproductive ecology (Deakos et al., 2011;Marshall & Bennett, 2010a;Stevens, 2016) and estimating abundance (Beale et al., 2019;Couturier et al., 2014;Venables, 2020). Regional reef manta ray [Mobula alfredi (Kreft, 1868)] photo-ID databases vary substantially in the total number of individuals identified over time, ranging from populations in the low hundreds (Axworthy et al., 2019;Carpentier et al., 2019;Deakos et al., 2011;Kashiwagi, 2014;Peel, 2019) to those in the thousands (Armstrong et al., 2019;Stevens, 2016;Venables, 2020). ...
Full-text available
The largest known reef manta ray (Mobula alfredi) population in Africa has been monitored for over 20 years at several locations on the coast of the Inhambane Province in southern Mozambique. However, prior to this study, little had been reported on the population dynamics of M. alfredi from Závora, a remote bay in the region. Photographic mark‐recapture was used to investigate the size and structure of M. alfredi that aggregate 'at ‘Red Sands’; a reef cleaning station in Závora Bay. An 11‐year photographic dataset was used to identify 583 M. alfredi individuals between 2010‐2021. More than half of M. alfredi individuals were resighted at least once, with most encounters (up to 18 for one individual) occurring during the peak sighting period in July‐November each year. An even sex ratio was observed, 44% females and 50% males, with no significant difference in resightings between the sexes. Pollock's Robust Design population models were used to estimate annual abundance, emigration, annual apparent survival, and capture probability at Red Sands from July‐November over a six year period (2016‐2021). Abundance estimates varied year to year, ranging from 35 (95% CI 30‐45), up to 233 (95% CI 224‐249) M. alfredi individuals. Given the seasonal affinity of M. alfredi observed at Red Sands, this study highlights the importance of understanding fine‐scale site use within the larger home range of this population to develop local management strategies. This article is protected by copyright. All rights reserved.
... The reef manta ray (Mobula alfredi) is a large, reefassociated, filter-feeding batoid that is widely distributed in tropical and subtropical regions of the Indo-Pacific [9]. While capable of long-distance movements spanning hundreds of kilometers [10][11][12], the species is commonly found in shallow coastal and lagoonal habitats [13][14][15]. ...
Full-text available
Background: Reef manta ray (Mobula alfredi) populations along the Northeastern African coastline are poorly studied. Identifying critical habitats for this species is essential for future research and conservation efforts. Dungonab Bay and Mukkawar Island National Park (DMNP), a component of a UNESCO World Heritage Site in Sudan, hosts the largest known M. alfredi aggregation in the Red Sea. Methods: A total of 19 individuals were tagged using surgically implanted acoustic tags and tracked within DMNP on an array of 15 strategically placed acoustic receivers in addition to two offshore receivers. Two of these acoustically monitored M. alfredi were also equipped with satellite linked archival tags and one individual was fitted with a satellite transmitting tag. Together, these data are used to describe approximately two years of residency and seasonal shifts in habitat use. Results: Tagged individuals were detected within the array on 96% of monitored days and recorded an average residence index of 0.39 across all receivers. Detections were recorded throughout the year, though some individuals were absent from the receiver array for weeks or months at a time, and generalized additive mixed models showed a clear seasonal pattern in presence with the highest probabilities of detection occurring in boreal fall. The models indicated that M. alfredi presence was highly correlated with increasing chlorophyll-a levels and weakly correlated with the full moon. Modeled biological factors, including sex and wingspan, had no influence on animal presence. Despite the high residency suggested by acoustic telemetry, satellite tag data and offshore acoustic detections in Sanganeb Atoll and Suedi Pass recorded individuals moving up to 125 km from the Bay. However, all these individuals were subsequently detected in the Bay, suggesting a strong degree of site fidelity at this location. Conclusions: The current study adds to growing evidence that M. alfredi are highly resident and site-attached to coastal bays and lagoons but display seasonal shifts in habitat use that are likely driven by resource availability. This information can be used to assist in managing and supporting sustainable ecotourism within the DMNP, part of a recently designated UNESCO World Heritage Site.
... birostris) are only sighted with regularity in the Maldives' southernmost atolls of Addu and Fuvahmulah, and only for a few months each year (March-April) during the transition from the NE to the SW Monsoon [27,35]. These southern Maldives sites are in close proximity to deep-water [27]; habitat where this species is often encountered throughout its range [36,37]. Re-sighting rates of individuals remain extremely low, which, combined with the seasonality of sightings, suggests a large transient population which utilises habitat away from the reef systems of the Maldives. ...
Full-text available
Despite being among the largest and most charismatic species in the marine environment, considerable gaps remain in our understanding of the behavioural ecology of manta rays (Mobula alfredi, M. birostris). Manta rays are often sighted in association with an array of smaller hitchhiker fish species, which utilise their hosts as a sanctuary for shelter, protection, and the sustenance they provide. Species interactions, rather than the species at the individual level, determine the ecological processes that drive community dynamics, support biodiversity and ecosystem health. Thus, understanding the associations within marine communities is critical to implementing effective conservation and management. However, the underlying patterns between manta rays, their symbionts, and other hitchhiker species remain elusive. Here, we explore the spatial and temporal variation in hitchhiker presence with M. alfredi and M. birostris throughout the Maldives and investigate the factors which may influence association using generalised linear mixed effects models (GLMM). For the first time, associations between M. alfredi and M. birostris with hitchhiker species other than those belonging to the family Echeneidae are described. A variation in the species of hitchhiker associated with M. alfredi and M. birostris was identified, with sharksucker remora (Echeneis naucrates) and giant remora (Remora remora) being the most common, respectively. Spatiotemporal variation in the presence of manta rays was identified as a driver for the occurrence of ephemeral hitchhiker associations. Near-term pregnant female M. alfredi, and M. alfredi at cleaning stations, had the highest likelihood of an association with adult E. naucrates. Juvenile E. naucrates were more likely to be associated with juvenile M. alfredi, and a seasonal trend in E. naucrates host association was identified. Remora were most likely to be present with female M. birostris, and a mean number of 1.5 ± 0.5 R. remora were observed per M. birostris. It is hoped these initial findings will serve as the basis for future work into the complex relationships between manta rays and their hitchhikers.
Although mobulids (Mobulidae) are threatened with extinction, basic information about their biology and ecology is still lacking. Therefore, we analyzed impacts of fishing, morphology, coloration, and stomach content of mobulid carcasses stranded on the coast of Ilha Comprida, southeastern Brazil, found in protected areas of sustainable use. The carcasses were of a juvenile female manta ray (believed to be Mobula cf. birostris), two adult females M. birostris (one with a partially aborted fetus), and two adult M. hypostoma (one female with an aborted fetus, and one male). The stomach content of a M. birostris consisted almost exclusively of a newly reported prey item, the sergestid Acetes americanus, highlighting the variation of prey items in the species’ diet. This is the first record of a pregnant M. birostris in the South Atlantic Ocean and the first account of A. americanus as a mobulid prey item. The reported mobulids have been impacted by fishing activities, even within sustainable use protected areas, highlighting the importance of improving surveillance in the area and the communication between the fishing communities, scientists, and managers for designing better conservation plans for the species. Future research and conservation efforts are urgently needed to better understand the spatial and temporal distribution of mobulids, as well of its prey A. americanus, to further confirm that mobulids use this site as a feeding and nursery area and to reduce the anthropogenic impacts on these endangered populations.
Full-text available
In 2018, the giant manta ray was listed as threatened under the U.S. Endangered Species Act. We integrated decades of sightings and survey effort data from multiple sources in a comprehensive species distribution modeling (SDM) framework to evaluate the distribution of giant manta rays off the eastern United States, including the Gulf of Mexico. Manta rays were most commonly detected at productive nearshore and shelf-edge upwelling zones at surface thermal frontal boundaries within a temperature range of approximately 20–30 °C. SDMs predicted highest nearshore occurrence off northeastern Florida during April, with the distribution extending northward along the shelf-edge as temperatures warm, leading to higher occurrences north of Cape Hatteras, North Carolina from June to October, and then south of Savannah, Georgia from November to March as temperatures cool. In the Gulf of Mexico, the highest nearshore occurrence was predicted around the Mississippi River delta from April to June and again from October to November. SDM predictions will allow resource managers to more effectively protect manta rays from fisheries bycatch, boat strikes, oil and gas activities, contaminants and pollutants, and other threats.
Full-text available
Data from 369 sightings of mobulid rays from St Helena Island, Cardno and Bonaparte seamounts in the South Atlantic are summarised. 50 % (183) of sightings were observed from a boat, 48 % (176) of sightings were encountered in water, of which 95 % (168) were whilst actively scuba diving. 2 % (10) of mobulid ray sightings were observed from land. Sightings data indicate that the Chilean devil ray Mobula tarapacana (Philippi, 1892) is a frequent visitor to St Helena and is present all year. We document the first photographic evidence of the presence of oceanic manta, Mobula birostris (Walbaum, 1792) at St Helena. Two solitary individuals were photographed off the north coast of St Helena in June 2018. These sightings confirm previous unverified reports on the species occurrence and extend the known distribution range of M. birostris in the open South Atlantic Ocean to 16°S.
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In 2018, the giant manta ray ( Manta birostris ) was listed as threatened under the U.S. Endangered Species Act. We integrated decades of sightings and survey effort data from multiple sources in a comprehensive species distribution modeling (SDM) framework to evaluate the distribution of giant manta rays off the eastern United States, including the Gulf of Mexico. Manta rays were most commonly detected at productive nearshore and shelf-edge upwelling zones at surface thermal frontal boundaries within a temperature range of approximately 15–30 °C. SDMs predicted high nearshore concentrations off Northeast Florida during April, with the distribution extending northward along the shelf-edge as temperatures warm, leading to higher occurrences north of Cape Hatteras, North Carolina from June to October, and then south of Savannah, Georgia from November to March as temperatures cool. In the Gulf of Mexico, the highest nearshore concentrations were predicted near the Mississippi River delta from April to June and again from October to November. SDM predictions will allow resource managers to more effectively protect manta rays from fisheries bycatch, boat strikes, oil and gas activities, contaminants and pollutants, and other threats.
ABSTRACT: Improving our knowledge on the behavior of threatened species is essential for developing effective conservation actions. The Paranaguá Estuarine Complex (PEC), southern Brazil, is the only estuary in the world where manta rays have been observed performing breaches seasonally. The exact role of this breaching behavior and the environmental factors connected to it are unknown. Our goals were to determine the spatial distribution, and the temporal and environmental factors that influence the breaching behavior of this endangered group in a dynamic estuarine habitat for the first time. Manta rays were observed breaching in the PEC during austral summer and early autumn, when the sea surface temperature (SST) and precipitation were high. Generalized additive models revealed that the presence and frequency of the breaches were both influenced by the SST and hours of daily effort, while the breaching frequency was also influenced by the wind direction and speed, percentage of moon illumination, and year. The breaches were mainly concentrated near the mouth of a river. Likely these factors influenced not only the occurrence and behavior of manta rays, but also the distribution of their food source, potentially providing optimal conditions for foraging and reproduction. Based on the coloration pattern, it is possible that the observations were of Mobula cf. birostris. These results provide valuable insights into the breaching behavior of manta rays in estuarine waters that will assist future conservation initiatives and research on their behavioral ecology, to optimize fishery management and contribute to developing sustainable ecotourism in the PEC.
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Data from 31 sightings of mobulid rays from New Zealand are summarised. Mobulid rays are common to locally abundant off north‐east North Island, New Zealand during summer and early autumn. Collection records and sightings data indicate the spine‐tailed devil ray (Mobula japanica) is the most abundant mobulid in New Zealand waters. Photographic and video evidence confirming the occurrence of the manta ray (Manta birostris) in New Zealand waters is presented. Estimated disc widths for New Zealand M. birostris ranged from 200 to 790 cm. Unlike in tropical regions, mobulid rays are largely confined to the epipelagic zone off New Zealand.
The taxonomic history of the genus Manta has been questionable and convoluted, with Manta having one of the most extensive generic and species synonymies of any living genus of cartilaginous fish. Having previously been considered a monotypic genus with a single recognized species, Manta birostris (Walbaum 1792), new evidence, in the form of morphological and meristic data, confirm that two visually distinct species occur, both with wide ranging distributions through many of the world’s oceans. Manta birostris stands as the most widely distributed member of the genus, while Manta alfredi (Krefft 1868), resurrected herein, represents a smaller, more tropical species. Separation of the two species is based on morphometric measurements and external characters including colouration, dentition, denticle and spine morphology, as well as size at maturity and maximum disc width. The two species of Manta are sympatric in some locations and allopatric in other regions. A visual key was constructed which highlights the conspicuous, diagnostic features of the two species using data collected throughout their respective geographical ranges. A third, putative species, referred to here as Manta sp. cf. birostris, in the Atlantic may be distinct from M. birostris, but further examination of specimens is necessary to clarify the taxonomic status of this variant manta ray. The results of this study will aid in the differentiation of members of this genus both in the field and in preserved specimens. The splitting of this long-standing monospecific genus will help to highlight the specific threats facing the different species of Manta (e.g. targeted fishing, bycatch fisheries, boat strikes and habitat degradation) and will ultimately assist in the correct assessment of their respective worldwide conservation status.
Manta rays, Manta alfredi, are a major attraction for tourist divers and snorkelers in the Republic of Maldives (central Indian Ocean). The aims of this study were to assess the extent and economic value of manta ray watching in the Maldives, by surveys of tourist numbers at manta diving sites, and from interviews with experienced divers. Ninety-one manta dive sites were identified, where tourists made an estimated 143,000 dives and over 14,000 snorkels annually during 2006-2008. This was estimated to be worth about US$8.1 million per year in direct revenue. The growth of manta ray watching has provided support for both research and conservation in the Maldives. However, there are indications that at the most popular manta dive sites the large numbers of visiting divers and snorkelers may be having a negative impact on manta numbers. There is a need for improved tourist education, and perhaps for regulation of diver numbers at some sites.