The National Marine Fisheries Service, a division of the National Oceanic and Atmospheric Administration, announced Friday that it has listed the giant manta ray as a threatened species under the Endangered Species Act.
The fisheries service takes primary responsibility for listing marine species under the act, while the U.S. Fish and Wildlife Service is responsible for listing land-based species. Species can be listed as endangered, meaning they are in imminent danger of extinction, or as threatened, meaning they are likely to become extinct within the foreseeable future. The measure of what constitutes foreseeable future is determined on a species-by-species basis. In this case, the agency says the mantas are likely to become extinct in several decades.
In the listing proposal last year, the agency found that giant manta rays are indeed imperiled, and the demand for manta ray gill rakers in Asian markets is one of the most significant threats they face. Gill rakers are cartilaginous projections that filter tiny prey like plankton that pass through the gills. The rakers are not involved in the animals’ breathing processes.
Some of the giant manta ray’s populations have been depleted by up to 95 percent, according to the agency.
The Defenders of Wildlife, a conservation group, petitioned to protect the giant manta and two other manta species in 2015.
“Dive operators in the Similan Islands, Thailand, have witnessed increased fishing for Manta spp.[subspecies] even in Thai National Marine Parks, and have reported consistent declines in Manta spp. sightings from 59 during the 2006-7 season down to 14 during the 2011-12 season (76 percent decline),” the Defender’s petition notes. “The available data indicates that Mozambique may be the only location in the Indian Ocean where giant manta rays have remained relatively stable in the short term … Sri Lanka has also reported giant manta ray declines, which is unsurprising given that 95 percent of the giant manta rays caught there are juveniles.”
The Center for Biological Diversity, a frequent petition and litigation partner with the Defenders on behalf of imperiled species, echoed this concern. “These gentle giants, with one of the largest brains of any fish, have been ruthlessly hunted for the manta ray gill plate trade,” said Catherine Kilduff, a senior attorney with the center, in an email. “Giant manta rays have declined in some areas up to 95 percent, so this listing comes not a moment too soon.”
Each giant manta can yield up to 15 pounds of dried gill rakers, which fetch up to $300 per pound. The bulk of the gill rakers trade – estimated at $5 million per year – funnels through China. But the current craze for the supposed healing properties of the rakers has little to do with traditional Chinese medicine. Instead, it is based in a belief that the food filtering properties of the gill rakers can transfer to filtering toxins from the human body, according to the Defenders’ petition.
In addition to fishing pressure and the lack of fishing regulation enforcement, rays face threats from water pollution, microplastics and other plastic debris, coral reef loss and bleaching, ocean acidification, climate change, shark and orca attacks, and heavy maritime traffic including tourist boats. This exacerbates the rays’ challenges with small populations, genetic isolation, and low reproduction rates.
Giant manta rays grow up to 25 feet long, can weigh up to 5,300 pounds, and live up to 40 years. However, they are not sexually mature until age 10, which contributes to low reproduction rates. With a gestation period lasting up to 14 months and a birth rate of one pup every 2 to 3 years, the species cannot quickly recover from heavy fishing.
Though the Defenders specifically asked for a critical habitat designation in their petition, the agency declined to specify habitat on the basis that it was “not determinable” due to a lack of data.
“The best available information indicates that the giant manta ray has experienced population declines of potentially significant magnitude within areas of the Indo-Pacific and eastern Pacific portions of its range, primarily due to fisheries-related mortality,” NOAA Fisheries spokeswoman Katherine Brogan said in an email. “In terms of U.S. fisheries, giant manta rays are a rare occurrence in the elasmobranch catch, and we find that the impact of these fisheries on the status of the giant manta ray is likely minimal.”
Elasmobranch refers to the group of fish encompassing rays, sharks and skates.
The Defenders also petitioned for protections for the Caribbean manta ray and the reef manta. But the government said the Caribbean manta ray did not meet the taxonomic criteria for listing as a species or subspecies, and also determined that the reef manta was not sufficiently threatened.
The Defenders maintain that the three species are similar and face similar threats.
“NMFS should also be aware that until the recent split of the genus Manta, all Manta Rays were classified as giant manta rays, and that the Manta Ray species share highly similar biological and behavioral characteristics and face very similar threats. As a result, species-specific threat data should also be used to inform consideration of threats to the other closely-related species,” the Defenders noted in their petition.
The Defenders did not respond to a request for comment on the listing by deadline.
The final listing of the giant manta ray as a threatened species under the Endangered Species Act will be effective 30 days from the planned publication date of Jan. 22.