First photographic evidence of oceanic manta rays (Mobula birostris) at two locations in Fiji

Until the revision of the genus Manta in 2009, when a second manta species (Manta alfredi) was resurrected based on morphological and meristic data, all available records in Fijian literature were recorded as Manta birostris, or commonly as the oceanic manta rays. Subsequently, documented sightings were recorded as M. alfredi.

Another reclassification of the genus Manta was undertaken in 2018 when both manta ray species (Manta alfredi, Manta birostris)
were moved to Mobula based on phylogenetic analysis.

Here, we present the first unequivocal evidence of oceanic manta rays (Mobula birostris) occurrence in Fijian waters.

Luke Gordon & Tom Vierus

Marine ecology consulting crew sighting mantas in Suva with Luke

Marine ecology consulting crew were part of this study in 2018 when we took out our boast MV KITE to Laucala Bay to sight mantas in Suva with Luke Gordon.

See our earlier article here…


In November 2018, two individuals were sighted foraging in Laucala Bay, a large lagoon adjacent to Suva, the capital city of Fiji.

Subsequently, three more individuals were sighted in December 2018, two individuals in July 2020, at least six individuals were observed in November 2021, and eight individuals in May/June 2022, all foraging in the same geographical area.

Unique ventral identification patterns could be obtained for nine individuals, and all nine individuals have been re-sighted since first identification, with one individual being documented in 2018, 2020, 2021 and 2022.

Two additional oceanic manta ray individuals were recorded in the Yasawa Island Group in the west of Fiji while passing through and foraging in a channel between Drawaqa and Naviti Island in April and September 2020.

We provide photographic identification of ten M. birostris individuals from two sites and discuss our findings in the context of local environmental parameters and other recorded sightings in the South Pacific region.

In light of the global extinction risk of M. birostris and the recent reclassification from Vulnerable to Endangered on the Red List of Threatened Species, the expansion of their known distribution range to Fijian waters and the recurrence of individuals over consecutive years in the same location adds valuable information for the development of effective and data-driven conservation strategies.

Manta rays (Mobula spp.) are large and charismatic zooplanktivorous elasmobranchs found in tropical and subtropical waters throughout the world (Marshall et al., 2020; Marshall et al., 2019:).

The two recognised species, Mobula birostris (oceanic manta ray) and Mobula alfredi (reef manta ray) belong to the family Mobulidae together with seven other ray species. Until 2009, the scientific consensus only included one manta ray species (Manta birostris).

This changed after a review by Marshall, Compagno & Bennett (2009), when a second species, Manta alfredi, was resurrected based on morphological and meristic data. Nine years later, a phylogenetic study by White et al. (2018) sequenced mitochondrial, and nuclear DNA of the complete taxon, and based on the results proposed moving both manta ray species from the genus Manta to the genus Mobula, changing their nomenclature to Mobula alfredi and Mobula birostris.

The authors noted that by solely sequencing mitochondrial DNA, both species were indistinguishable, but when incorporating nuclear DNA in combination with morphological data, results indeed supported the proposed taxonomic changes.

Speciation has occurred relatively recently in evolutionary terms, and the close genetic relationship is likely a result of post-divergence gene flow through hybridisation (Kashiwagi et al., 2012). Interestingly, a recent study by Hosegood et al. (2020) additionally presents evidence of a putative third manta ray species in the Gulf of Mexico, indicating potential further taxonomic changes to the Mobula genus. 

The reef manta ray, M. alfredi, is generally observed in nearshore areas or in the vicinity of continental coastlines, exhibiting small home ranges and a high degree of site fidelity (Couturier et al., 2011), albeit exceptions have been observed, such as a reef manta ray recorded at Cocos Island nearly 6,000 km from the nearest confirmed sighting (Arauz et al., 2019). The more widely distributed oceanic manta ray, M. birostris, occurs in all three major oceans (Marshall et al., 2020), often observed in pelagic environments, such as offshore seamounts, pinnacles or oceanic islands (Marshall, Compagno & Bennett, 2009; Fig. 1). 

Similar to other elasmobranchs, targeted and untargeted fisheries coupled with life-history traits, such as slow growth, late maturation, long gestation periods and low fecundity render both manta species particularly vulnerable to overexploitation (Couturier et al., 2012; Dulvy et al., 2014; Pardo et al., 2016).

Declining populations due to the aforementioned factors led to conservation concerns for both species, with M. alfredi listed as Vulnerable and M. birostris listed as Endangered to Extinction on the IUCN Red List of Threatened Species (Marshall et al., 2019; Marshall et al., 2020).

On a national level, both manta ray species are legally protected in Fiji by the ‘Endangered and Protected Species Act (EPS)’ adopted in 2002, which requires permits to trade or land species listed in Appendix I, II or III of CITES, the ‘Convention on International Trade on Endangered Species of Wild Fauna and Flora’  (Fiji Government, 2002).

Similarly, Fiji’s ‘Offshore Fisheries Management Act (OFMA)’ adopted in 2012, forbids the killing, taking, landing, selling and transporting of species listed in Appendix I and II of CITES (Fiji Government, 2012).

Besides introducing national legislation, Fiji has repeatedly advocated for more protection on an international level. 

For example, in 2014, Fiji led the successful proposal for inclusion of all Mobula species in Appendix II of the ‘Convention on the Conservation of Migratory Species’ (Convention of Migratory Species, 2014) and in 2016, the successful proposal for inclusion of the same group in Appendix II of CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora, 2016).

Fiji reaffirmed their domestic ambitions at the UN Ocean Conference in New York in 2017 by committing to the ‘‘conservation and management of all species of sharks and rays and their critical habitats within Fijian waters’’ (United Nations, 2017).

Surprisingly, to date, there are no documented records of M. birostris in Fiji’s waters after the resurrection of M. alfredi in 2009 besides brief mentions in the catch statistics of Fijian longline pelagic fisheries (Piovano & Gilman, 2017). Earlier records of Manta birostris can be found in Fijian literature, for example, a 300–400 kg specimen recorded off Rotuma in 1983 (Fijian Fisheries Division, 1983).

While some reliable reef manta aggregation sites are known throughout the country and opportunistic Mobula spp. sightings are commonly reported by recreational divers, fishermen and tourism operators, detailed information on habitat preferences and distribution within the country is generally lacking.

M. birostris, oceanic manta rays in Yasawas Fiji
Map of the Yasawa Islands and Viti Levu, Fiji’s main island. Inset (top right) displays a close-up map of the Manta Channel between Drawaqa Island and Naviti Island.

Drawaqa island in the Yasawa Island Group

Several Fiji-based tourism operators offer reef manta ray snorkelling activities, most notably Barefoot Manta, an ecotourism resort based on Drawaqa island in the Yasawa Island Group, approximately 40 km north-west from Viti Levu.

The island group consists of 11 main volcanic islands running 90 km to the north-east (Ward & Beggs, 2007). A 250 m long, 300 m wide and approx.

A 7 m deep channel located towards the southern end of Drawaqa Island and the largest island in the chain, Naviti Island, is a known reef manta ray aggregation site.

From May to October aggregations of up to 15 reef manta rays can be observed in the channel (Murphy, Campbell & Drew, 2018).

In addition to feeding on plankton, the reef manta rays also opportunistically utilise a cleaning station in the passage.

Kokomo Private Island Fiji

Similarly, the waters off Kokomo Private Island Fiji, a luxury resort based in the south of the country on Yaukuve Levu Island, part of an island chain to the north of Kadavu Island, are home to several foraging sites and cleaning stations with regular sightings from April-December and a peak in sightings from May–October.

Large aggregations have been recorded at these sites with 65+ individuals foraging at the same time, currently the largest aggregation of reef manta rays known in Fiji (L Gordon, 2020, pers. obs).

Manta Project Fiji (MPF), established in 2012 as an affiliate of the Manta Trust, has been cataloging reported manta ray sightings across the country and currently manages a database containing 425 identified M. alfredi individuals.

Prior to this study, no oceanic manta rays had been reliably confirmed through photographs or video in Fijian waters and were absent from the database.

M. birostris, oceanic manta rays in SUva
Map of the greater Suva area which includes Laucala Bay, Suva city, Suva Harbour, the Rewa River and the Rewa Estuary. The foraging area of the observed oceanic manta rays is located at the southern-western end of Laucala Bay (highlighted) near one of the channels in the barrier reef.

Laucala Bay – Suva, Fiji’s capital

Adjacent to Suva, Fiji’s capital, lies Laucala Bay, a relatively flat coastal lagoon enclosed by a barrier reef (Fig. 2).

Here, reef manta rays (Mobula alfredi) are commonly observed foraging and at least one individual was captured here by local fishermen in August 2021.

Laucala Bay lies between the Suva peninsula in the west (where a hilly environment separates it from Suva Harbour) and the delta of Fiji’s largest river, the Rewa, in the east (Fig. 2).

The tidal range of the bay lies between 0.9–1.33 m, with an average depth of 9–15 m and a maximum depth of 30–40 m (Morrison, Narayan & Gangaiya, 2001; Koliyavu et al., 2021).

During high tide, Laucala Bay’s surface area extends to 4,500 ha, with several emerging mudflats and sandbanks shrinking it to 3,900 ha during low tide (Morrison, Narayan & Gangaiya, 2001).

Besides being located adjacent to the Rewa delta, several rivers feed into the bay area shedding large amounts of freshwater into the area with limited exchange towards the oceans due to the reef system sheltering it from the open ocean (Koliyavu et al., 2021).

Additionally, the bay receives treated domestic, commercial and industrial wastewater discharged from the Kinoya sewage treatment plant into the northern part of the bay (Fig. 2; Ferreira et al., 2020).

Identification photographs

  • With comparison to M. alfredi. Manta identification names are shown at the bottom left, e.g., ‘FJ-MB-0001’.
  • Two individuals (FJ-MB-0001, FJ-MB-0002) were identified underwater while the remaining seven were photographed or filmed utilising a drone.
  • White arrows (A) and (C) indicate key morphological features for M. birostris: (A) shows the distinctive grey V-shaped margin along the posterior edge of the pectoral fins; and (C) shows the white dorsal shoulder markings that form two mirror image right-angled triangles.
  • Ventral spots clustered around the lower abdomen region which are used for identification are indicated by (B). White arrows (D) and (E) indicate key morphological features for M. alfredi: (D) shows ventral identification spots clustered between the gill slits and across trailing edge of pectoral fins; and (E) shows the white blurred ‘V’ dorsal markings.
  • FJ-MB-0001 image shows two sightings, the original sighting (inset, bottom right) from 02.12.2018 and the most recent from 24.11.2021. .
M. birostris, oceanic manta rays
Identification photographs of nine M. birostris individuals sighted in Laucala Bay adjacent to Suva, Fiji’s capital city. Photographs taken by Tom Vierus, Luke Gordon and Cliona O’Flaherty

Unequivocal evidence of oceanic manta ray occurrence within Fijian waters.

This paper discusses all recorded M. birostris sightings in Fijian waters to date, presenting photographic evidence of 9 M. birostris individuals foraging in Laucala Bay near Suva and two additional M. birostris, oceanic manta rays, sightings in the Yasawa Island Group and explores the sightings in relation to local environmental parameters.

It thus provides the first unequivocal evidence of oceanic manta rays occurrence within Fijian waters.

Luke Gordon & Tom Vierus
  • Submitted 22 April 2022
  • Accepted 21 July 2022
  • Published 7 September 2022

Corresponding author: Luke Gordon, [email protected]

  • Gordon L, Vierus T. 2022. First photographic evidence of oceanic manta rays (Mobula birostris) at two locations in the Fiji islands. PeerJ 10:e13883

How to tell the difference between Reef Manta Ray ( Mobula alfredi) and Oceanic Manta Ray (Mobula birostris)

See full article here…
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