Both recognized species of manta ray are formally threatened with extinction. The reef manta ray (Mobula alfredi) is classified as Vulnerable by the International Union for Conservation of Nature, meaning it faces a high risk of extinction in the wild, while the oceanic manta ray (Mobula birostris) holds the more severe status of Endangered. Their situation is shaped by an unfortunate combination: they reproduce more slowly than almost any other fish, and they face a growing list of human-caused threats that their biology leaves them poorly equipped to absorb.
Two Species, Two Threat Levels
Manta rays were once lumped into a single species, but researchers split them into the reef manta ray and the larger oceanic manta ray. The reef manta ray tends to stay closer to coastlines and coral reefs, while the oceanic manta ray roams open water and can grow to disc widths exceeding seven meters. Their IUCN assessments reflect different scales of pressure. The reef manta ray’s global population is suspected to have declined by roughly 30 to 49 percent over the past three generation lengths, a window of about 87 years. Where reef mantas receive some level of protection, such as in Australia, Japan, the Maldives, and certain marine protected areas in Indonesia, numbers appear stable. But in places with heavier fishing pressure, declines have been catastrophic: sighting records in southern Mozambique fell by 98 percent over a 15-year period, and parts of Maui, Hawaii, saw a 94 percent drop, with many surviving individuals bearing entanglement scars from fishing gear.1The IUCN Red List of Threatened Species. Mobula alfredi — Reef Manta Ray
The oceanic manta ray’s Endangered listing reflects even greater concern, driven by its wider exposure to open-ocean fisheries and the difficulty of protecting a species that crosses international boundaries. Adding a layer of complexity, genetic and taxonomic work suggests that manta rays in the Western Atlantic may represent a separate, not-yet-formally-described species, meaning the conservation picture could shift further as scientists work out exactly how many species exist and where their boundaries lie.2Endangered Species Research. Urban manta rays: potential manta ray nursery habitat along a highly developed Florida coastline
Why Manta Rays Cannot Bounce Back Quickly
Most fish cope with predation and fishing by producing enormous numbers of offspring. Manta rays do the opposite. A female typically gives birth to just one pup per litter, occasionally two, after a gestation period of roughly a year. There is strong evidence that many females reproduce only once every two years. Males may reach sexual maturity at around three to six years, but females likely take eight to ten years before they can breed.3PubMed Central. Diagnosing the dangerous demography of manta rays using life history theory This reproductive pace is closer to that of a large mammal than to a typical fish. When a population takes a hit from overfishing or habitat loss, the recovery timeline is measured in decades, not seasons. Even modest, sustained fishing pressure can push a local population toward collapse because losses outpace the rate at which new individuals enter the population.
The Gill Plate Trade
The single largest direct driver of manta ray mortality is targeted fishing for their gill plates, the feathery structures they use to filter plankton from the water. Dried gill plates, sold under the trade name “pengyusai,” became a valued commodity in Asian dried-seafood and traditional Chinese medicine markets. Vendors market them for ailments ranging from acne to cancer and as a general health tonic, despite the fact that pengyusai is a recent addition to traditional Chinese medicine literature and is rarely prescribed by actual practitioners. The demand is driven almost entirely by over-the-counter sales and aggressive vendor marketing rather than by longstanding medical tradition.4Aquatic Conservation: Marine and Freshwater Ecosystems. Characterization of the trade in manta and devil ray gill plates in China and South‐east Asia through trader surveys
This trade has had outsized effects because it creates financial incentive to kill animals whose populations simply cannot sustain the harvest. In Indonesia, one of the world’s most important manta ray habitats, fishery surveys documented unsustainable catch rates and associated population declines. The total annual income from manta ray fisheries there was estimated at roughly $442,000, with about 94 percent coming from gill plates destined for export.5PLoS ONE. The Global Economic Impact of Manta Ray Watching Tourism Both manta species were listed on Appendix II of the Convention on International Trade in Endangered Species (CITES) in 2013, which requires exporting countries to demonstrate that trade is not detrimental to wild populations. Whether these regulations have translated into real on-the-ground conservation gains is an ongoing question, and researchers have stressed that robust impact assessments are needed to determine whether CITES listings and associated domestic regulations actually reduce mortality.
Bycatch in Commercial Fisheries
Even where manta rays are not deliberately targeted, they die as bycatch in industrial fishing operations. Tropical tuna purse seine fisheries are a particularly significant source of manta and devil ray mortality worldwide. These massive nets encircle entire schools of tuna but sweep up everything else swimming nearby, and manta rays are both large enough and slow enough to get trapped. Recent research has shown that training vessel crews in best handling and rapid release practices can substantially reduce the number of mantas that die after being caught, offering a practical path forward that does not require eliminating the fishery itself.6PubMed Central. Evidence for a fisher-designed solution to manta and devil ray bycatch in tuna fisheries The challenge is scaling these practices across fleets operating in dozens of countries with varying levels of enforcement.
Microplastic Contamination
Manta rays are filter feeders, meaning they swim with their mouths open and strain plankton from the water column. That feeding strategy makes them especially liable to ingest microplastics, which accumulate in the same surface layers where their food concentrates.7Conservation Science and Practice. No escape from microplastics: Contamination of reef manta ray feeding areas in a remote, protected archipelago The problem is not limited to polluted coastlines. Sampling at D’Arros Island and St. Joseph Atoll in the Seychelles, a remote archipelago far from major industrial centers, found microplastics in the water at manta ray feeding sites. The most abundant polymer detected was polybutylene terephthalate, and several of the polymers identified were rated as “very high” concern for biological harm, including polyurethane, polyacrylonitrile, and polyvinyl chloride.8PubMed. A microplastic meal: A baseline assessment of microplastic polymer presence within manta-ray (Mobula alfredi) feeding grounds at D’Arros Island and the St. Joseph Atoll
What this contamination actually does to manta ray health over the long term is not yet clear. The Seychelles study found no significant relationship between total microplastic abundance and zooplankton biomass at the sites sampled, meaning mantas do not necessarily swallow more plastic when they feed more intensely at that location. But the sheer presence of high-concern polymers in remote, protected waters underscores that no manta ray habitat is truly free from this threat. This is a newer area of research, and the physiological consequences of chronic low-level microplastic ingestion in a species that lives for decades are still being worked out.
Genetically Isolated Populations Are More Vulnerable Than They Look
From the surface, it might seem that a manta ray’s ability to swim long distances would keep populations well connected. Genetic research tells a different story. In New Caledonia, reef manta rays at three different cleaning station aggregation sites showed detectable genetic differences from one another despite the sites being relatively close together. At the regional scale, manta rays in New Caledonia and eastern Australia were genetically distinct populations, with gene flow detected only in one direction, from New Caledonia toward Australia.9Endangered Species Research. Evidence of fine-scale genetic structure for reef manta rays Mobula alfredi in New Caledonia
A similar pattern holds for oceanic manta rays in the Eastern Tropical Pacific, where genetic analysis identified two separate populations at the Galápagos Islands and mainland Ecuador, with low gene flow between them.10Marine Ecology Progress Series. Exploring the genetic diversity and population structure of Mobula birostris in two key aggregation zones in the Eastern Tropical Pacific The practical consequence is that losing a local population is not just a numbers problem. It represents a loss of unique genetic diversity that will not be replaced by immigration from neighboring groups. Conservation strategies that assume a single well-mixed global population would underestimate the damage caused by localized fishing pressure or habitat degradation. Each region needs to be managed as its own conservation unit.
A Living Manta Ray Is Worth Far More Than a Dead One
One of the more compelling arguments for manta ray protection comes from straightforward economics. Manta ray watching tourism generates an estimated $140 million per year globally, dwarfing the roughly $5 million annual trade in manta ray gill plates.5PLoS ONE. The Global Economic Impact of Manta Ray Watching Tourism Indonesia offers a particularly stark illustration: annual spending on manta ray diving tourism there was estimated at close to $10.7 million, with a broader direct economic impact exceeding $15 million per year, while the total income from Indonesian manta ray fisheries came to about $442,000. A single manta ray, according to analysis by Conservation International Indonesia, can generate roughly one million dollars in tourism revenue over its lifetime, compared to about $500 when killed.11IntechOpen. Manta Ray Tourism
These numbers have been influential in persuading governments to create manta ray sanctuaries. Indonesia declared the world’s largest manta ray sanctuary in 2014, covering nearly six million square kilometers of its waters. Ecuador, the Maldives, and several other countries have followed with their own protections. The economic case does not resolve every conflict, since the fishers who catch mantas and the communities that benefit from tourism are often not the same people, and the distribution of tourism revenue within coastal communities is uneven. But the gap between the value of a living manta and a dead one is so large that it has shifted policy in countries where conservation arguments alone had limited traction.
When Tourism Itself Becomes a Threat
The same tourism revenue that justifies protection can also become a source of stress for the animals it is supposed to save. A drone-based study of juvenile manta rays found that the animals spent about 37 percent of their time actively avoiding divers. The effect varied between individuals: some mantas were highly avoidant, spending up to 70 percent of their time in avoidance behavior when divers were present, while others seemed relatively unperturbed. Manta rays in the presence of divers also spent significantly more time with their cephalic fins unfurled, a behavioral shift that may interfere with feeding.12Drones. Using Drone Footage to Analyze the Effect of Diver Presence on Juvenile Manta Ray Behavior
For small or vulnerable local populations, this kind of chronic disturbance could reduce the time mantas spend feeding and resting at key sites, with downstream effects on body condition and reproductive success. The researchers who conducted the study concluded that the population they observed was unsuitable for expanded tourism development. This does not mean manta ray tourism is inherently harmful, but it does mean that tourism operations need to be managed carefully, with limits on diver numbers, approach distances, and time spent near the animals, especially at nursery and feeding sites used by juveniles.
Deep Divers and Ecological Connectors
Manta rays play a role in ocean ecosystems that goes beyond their place in the food web. Satellite tagging of reef manta rays revealed that they regularly dive far deeper than their shallow-reef reputation suggests. In one study, tagged individuals performed repeated dives below 150 meters, with one individual reaching 432 meters. This behavior means manta rays act as ecological connectors between shallow reef habitats and the deep ocean, transporting nutrients and energy between layers of the water column that are otherwise largely separate.13PubMed Central. Diving behavior of the reef manta ray links coral reefs with adjacent deep pelagic habitats The tagged mantas also appeared to use a gliding technique during these deep dives, making them one of only a handful of marine species known to exploit this energy-saving movement strategy. Losing manta rays from a reef system would not just remove a charismatic animal; it would sever a biological link between two major ocean zones.
New Tools for Tracking an Elusive Animal
One of the persistent challenges in manta ray conservation is simply knowing where the animals are and how many exist. Traditional population surveys rely on visual sightings, often by divers at known aggregation sites, which introduces serious biases: you only count mantas where and when you happen to look. Environmental DNA, or eDNA, is changing this. Researchers around Oahu, Hawaii, used plankton net samples to detect manta ray DNA in the water, finding both spatial and temporal variation in manta distribution that visual surveys alone would have missed. Most detections occurred off the East Shore of Oahu, in Kāne’ohe Bay.14Frontiers in Marine Science. Elusive and vulnerable: evaluating spatial and temporal variation in the distribution of manta rays around O’ahu using environmental DNA This approach is noninvasive and does not depend on the animal being visible to a human observer, making it a promising complement to photo identification databases that have been the backbone of manta research for decades.
Photo identification remains valuable. Each manta ray carries a unique pattern of spots on its underside, functioning like a fingerprint. Citizen science databases built from diver photographs have documented individual mantas across years and locations. In South Africa, for example, photo-ID studies confirmed both reef and oceanic manta rays in the country’s waters, with reef mantas concentrated in the iSimangaliso Wetland Park and oceanic mantas found at Aliwal Shoal.15Environmental Biology of Fishes. Preliminary insights into manta ray (Mobula alfredi and M. birostris) population demographics and distribution in South Africa Combining photo-ID with eDNA and satellite tagging gives researchers a much fuller picture of population size, movement, and site fidelity than any single method can provide. For a species whose future depends on getting management decisions right at the local level, that kind of data resolution matters enormously.