A national population database for manta rays has been compiled from four identified hotspots for the species in the Philippines, three of which are in the waters of Palawan.
The new scientific study was led by the Large Marine Vertebrates Research Institute Philippines (LAMAVE) with partners and the public.
It is made up of data from the Tubbataha Reefs Natural Park in Cagayancillo municipality, Puerto Princesa City, Taytay town, and San Jacinto in the Ticao-Burias Pass Protected Seascape, where they have been observed frequently aggregating.
LAMAVE explained in a statement sent by director Sally Snow that the sightings were gathered by their dedicated in-water research efforts, partners, citizen science contributions from dive centers, digital submissions on platforms such as mantamatcher.org, and searches on social media platforms Facebook, Instagram, and YouTube.
Manta rays have been monitored present in at least22 different locations, four of which have been considered as “hotspots,” or places where they tend to congregate. LAMAVE said these four sites accounted for 89% of all the individual manta rays and specific behaviours were observed including cleaning, courtship and feeding.
Presence of reef mantas and oceanic mantas
“A total of 2,659 manta ray sightings were analysed by the team and from those, 499 individual manta rays were identified using photo-identification methods, which use the unique spot pattern on the ventral side (belly) of the manta ray,” it said.
“These individuals were encountered in 22 different sites across the Philippines, 11 of which both reef manta and oceanic mantas were observed,” the marine vertebrates research institute added.
Nonie Enolva, senior fishing regulations officer and chief of the Fisheries Resource Management Section of the Bureau of Fisheries and Aquatic Resources (BFAR) in Region 5, said Ticao-Burias Pass Protected Seascape is one of the Bicol Region’s key marine biodiversity areas that is home to filter-feeding megafauna like whale sharks, megamouth sharks and mobulas.
“The area has been known to be rich in plankton and other primary producers at the trophic level. The preponderance of visits of these megafaunas is greatly attributed to how rich the Ticao Pass is in terms of the primary food source that has been provided for them. Thus, the protection of this important fishing ground would also mean the protection of the many marine species that are dependent on it,” Enolva said.
In addition to necessitating an Ecosystems Approach to Fisheries Management, the implementation of Fisheries Management Area 7, which encompasses Ticao Pass, would necessitate the implementation of policies that protect important marine species.
The oceanic manta (Mobula birostris) species was represented by 107 individuals in the national catalog, and resighting of the species provided information regarding their migration patterns.
“One female manta first sighted in Daanbantayan, Cebu in 2009, became the first recorded movement of an oceanic manta between sites in the Philippines when she was resighted in San Jacinto in 2014 and then back again in Daanbantayan in 2017. Another individual made a similar journey in 2017, covering ~150 km (straight-line movement) in five days,” LAMAVE said.
Other records from Daanbantayan also revealed the longest resighting interval, with two manta rays observed in the region after an 8-year absence. Six additional individuals were spotted in the area in at least two different years, indicating the importance of the area to the species.
Ticao, Masbate, and Palawan hotspots for reef mantas
A total of 392 individuals of the reef manta (Mobula alfredi) species have been identified based on sighting records collected over a period of 16 years between 2004 and 2020.
More than 90% of these individuals were found in three locations: San Jacinto (Ticao-Burias Pass Protected Seascape), Taytay, and in Cagayancillo, the home of the Tubbataha Reefs Natural Park in Palawan.
“In these areas 66-80% of the mantas identified were seen more than once, most often at cleaning stations – small patches of coral that house cleaning fish. The fact that two of these hotspots are within protected areas (Ticao-Burias Pass Protected Area and Tubbataha Reefs Natural Park) highlights the importance of these areas for the species and why the continued efforts to conserve them are crucial,” LAMAVE stated.
Both species still under threat
According to LAMAVE, the new study identifies key threats that are still a problem for these species, such as observations of fishery-injuries and damage to cleaning stations.
A quarter of the identified animals in San Jacinto and Taytay exhibited fishery-related injuries, such as damaged or absent fins or severe cuts.
Another threat is the destruction of cleaning stations, LAMAVE said. In San Jacinto, the cleaning sites are characterized by an abundance of fishing gear entangled in the reef, causing damage to or destruction of this delicate habitat.
Despite increased diving activity, the number of sightings of oceanic manta rays in Daanbantayan decreased from 73 between 2006 and 2012 to 16 between 2013 and 2019. Similar trends were observed in San Jacinto, with 15 sightings between 2013 and 2014 and only three between 2017 and 2019.
“This is an alarming 80% decline in sighting frequency and may be attributed to fishing activities in part of its assumed population range, such as in the Bohol Sea which saw at least 100 oceanic mantas landed per season in the Bohol Sea up until 2017,” added LAMAVE.
“The species has a population recovery time of over 37 years so protecting the remaining individuals is fundamental if we are to help the species recover,” it added.
LAMAVE said to protect the manta rays, marine protected areas and rules about fishing gear should be put in place right away at these sensitive sites, especially in places like Taytay and Puerto Princesa City, which are known hotspots but don’t have species-specific protection yet.