Manta rays, recognized by their expansive, wing-like pectoral fins and intelligent behavior, are among the ocean’s most charismatic filter feeders. These large fish inhabit tropical, subtropical, and temperate waters worldwide, relying on plankton for sustenance. Despite their impressive size and widespread distribution, these gentle giants reproduce slowly and are susceptible to external pressures. The two recognized species of manta rays are currently listed on the global conservation watch list, indicating a threat to their survival.
Conservation Status of Manta Ray Species
The conservation status of manta rays depends on the two distinct species, each facing a different level of threat according to the International Union for Conservation of Nature (IUCN) Red List. The Giant Oceanic Manta Ray (Mobula birostris) is classified as Endangered globally. This species is the world’s largest ray, highly migratory, and travels vast distances in open, oceanic waters.
The Reef Manta Ray (Mobula alfredi) is classified as Vulnerable. This ray is commonly found in nearshore environments, such as productive coastlines, coral reefs, and shallow island systems, exhibiting high site fidelity. The differences in habitat influence their threat levels, as the wide-ranging oceanic species is more exposed to pelagic fishing pressure across international waters.
The vulnerability of both species stems from extremely slow reproduction. Female manta rays typically produce only a single pup every one to three years after a gestation period of over a year. This low reproductive output prevents populations from recovering quickly from exploitation, making them sensitive to human-caused mortality. Population declines for the oceanic species have been recorded, with sightings dropping up to 94% over a 15-year period in some areas.
Primary Drivers of Population Decline
The most significant threat driving the manta ray’s decline is targeted fishing for their gill plates, known as gill rakers. These cartilaginous filtering structures are dried and sold under the trade name pengyusai for use in traditional medicine markets, despite a lack of scientific evidence supporting their purported health benefits. This demand has created a lucrative international trade, providing the economic incentive for unregulated fishing operations in critical manta ray habitats.
Incidental capture, or bycatch, in large-scale commercial fisheries is a secondary threat. The Giant Oceanic Manta Ray is susceptible to being accidentally caught in industrial purse-seine and artisanal gillnet operations. Although unintended, rays caught as bycatch are often retained and sold to the gill raker market, contributing to population depletion.
Habitat degradation also stresses populations, particularly the coastal Reef Manta Ray, which relies on specific sites for feeding and cleaning. Coastal pollution, entanglement in discarded fishing gear, and injury from boat strikes pose ongoing threats in nearshore habitats. Manta rays are also susceptible to disturbance at aggregation sites, where unregulated tourism or coastal development can disrupt their natural behaviors.
Global and National Protection Measures
International agreements curb the unsustainable trade driving the decline of manta ray populations. The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) regulates the global market. All species of manta and devil rays were recently uplisted to CITES Appendix I, which prohibits all international commercial trade in their products, including gill plates.
This progression of protection highlights the escalating concern over their status. Previously, the species were listed on CITES Appendix II, requiring exporting countries to prove trade was legal and non-detrimental. The Giant Oceanic Manta Ray is also listed on Appendices I and II of the Convention on Migratory Species (CMS), committing member nations to strict national protections and coordinated conservation efforts across their migratory range.
Numerous countries and local governments have established Marine Protected Areas (MPAs) to safeguard important aggregation sites, such as feeding and cleaning stations. For instance, large concentrations of manta rays are found in protected zones like the Galapagos Marine Reserve and Machalilla National Park in Ecuador. These national protections are vital for protecting resident Reef Manta Ray populations and providing safe havens for the migratory oceanic species.