Sicklefin Devil Ray, Mobula tarapacana
Sicklefin Devil Ray, Mobula tarapacana, Juveniles. Photograph taken “outside” along the eastern section of the Puerto Los Cabos Marina breakwater, Baja California Sur, August 2020. Frequent visitors to the greater Los Cabos area. Photography courtesy of Robert North. A difficult identification with a 90% confidence level of correctness.
Sicklefin Devil Ray, Mobula tarapacana. One of four fish caught as “catch and release” in a gill net set for about 30 minutes in coastal waters off Puerto Adolfo Lopez Mateos, August 2017. Wingspan: approximately 1.52 m (5 feet 0 inches). Weight: approximately 125 kg (275 lbs). Caught with Captain Jimmy Camacho, pictured above, Puerto Adolfo Lopez Mateos, Baja California.
The Sicklefin Devil Ray, Mobula tarapacana, is a member of the Devil Ray or Manta Ray or Mobulidae Family, that is also known as the Chilean Devil Ray and in Mexico as manta cornuda. Globally, there are twelve species in the genus Mobula, of which five are found in Mexican waters, one in the Atlantic, three in the Pacific, and one in both the Atlantic and Pacific Oceans.
The Sicklefin Devil Ray is a large-sized devil ray. They are brown to olive-green dorsally and white at the front, then abruptly change to gray posteriorly and ventrally. They have a projecting and relatively narrow head with short head horns. The front edge of their snout between the horns is strongly concave. Their wings are large, triangular, and strongly curved backwards, and their front margins end below and before the spiracle. They have a short keel above their spiracle which is an elongated slit. Their mouth is located on the underside of their head. They have 94 to 135 teeth on their upper jaw and 107 to 153 teeth on their lower jaw; their teeth are hexagonal with pitted tips and comb-like rear edges set in a large mosaic pattern and cover about 70% of the mouth width. Their gill filter plates are fused along their length with broadly rounded end lobes. They have a relatively short tail that measures less than half the disc width and has scales but no spine. Tail length versus disc width is an important marker for accurate identification, however, many mobulas lose parts of their tail fairly frequently, which lessens the usefulness of this parameter. Their body is covered with minute thick needle-like denticles.
The Sicklefin Devil Ray is primarily an oceanic species but are also found in coastal waters and are seasonal visitors to coastlines with regular upwelling around oceanic islands, near offshore pinnacles, and seamounts. They can be found at depths up to 1,900 m (6,232 feet). They are highly migratory traveling in schools or as solitary individuals and making migrations of up to 3,800 km (2,360 miles). They frequent the Sea of Cortez during the summer and autumn months. They reach a maximum disc width of 3.7 m (12 feet) and can weigh up to 350 kg (770 lbs) with females being slightly bigger than males. They are truly massive animals! Due to their massive size and strength, they are difficult to handle and photograph as “catch and release.” They feed on planktonic crustaceans. In Mexico, they most commonly consume Krill, Nyctiphanes simplex. Reproduction occurs via ovoviviparity with internal fertilization. Each female has one pup annually which have wingspans ranging from 1.17 m (3 feet 8 inches) to 1.32 m (4 feet 4 inches). Embryos are initially fed on yolk then receive additional nourishment from their mother by indirect adsorption of uterine fluid enriched with mucus, fat, and protein. They are born live as miniature adults. They reach sexual maturity in 5 to 6 years. They are an exceedingly rare and poorly studied species with very limited information available about their lifestyle and behavioral patterns including specific details on catch, age, growth, movement patterns, diet, habitat use, and range. They have a lifespan of up to fourteen years.
The Sicklefin Devil Ray is a resident of all Mexican waters of both the Atlantic and Pacific Oceans with the exception that they are absent from the central west and northwest coasts of Baja in the Pacific.
The Sicklefin Devil Ray is very similar in appearance to, and difficult to separate from, the four other Mobulidae Rays found in Mexican waters of the Pacific namely, the Giant Manta, Manta birostris (mouth opens at front), the Pygmy Devil Ray, Mobula munkiana (dark-colored underside of outer half of disc), the Smoothtail Devil Ray, Mobula thurstoni (small green patch on ventral side), and the Spinetail Mobula, Mobula japanica (tail longer than disc width; disc width greater than 3 m).
From a conservation perspective the Sicklefin Devil Ray is currently considered Vulnerable. They have extremely low reproductive rates with just 1 pup per year. All the mobulas are poorly regulated and unmonitored globally. Catch levels are seldom reported and the Sicklefin Devil Ray is subject to misidentification. It is currently believed that their populations have declined by as much as 50% in many areas over the last 10 years. They are protected nationally in Mexico and have been added to the global list of fish at high risk of extinction. They are prone to high illegal catches and high mortality levels but many are still retained illegally. The Sicklefin Devil Ray is taken as a targeted catch or a discarded by-catch by both artisanal and commercial fishermen utilizing long lines, purse seines (mostly from tuna fisheries) and gill nets throughout the Atlantic, Pacific, and Indian Oceans. If released they have very low survival levels. Annual global catch levels are estimated at 100,000 individuals per year. Although their meat is considered marginal for human consumption and retained only by subsistence fishermen some are used locally as animal feed, fishmeal, leather products, shark bait, and as a source of chondroitin sulfate. They have also become the target of increasing commercial interest due to the Chinese Medicinal Trade. Their feathery gill plates, which number 5 pairs per fish and encircle each gill slit, have become in vogue by the creation of an artificial market commanding exorbitant prices ($130 per pound) that promote gill plates for the treatment of a wide variety of human diseases including asthma, cancer, chicken pox, skin rashes, and as an anti-inflammatory agent that can detox the bloodstream by removing toxins and boosting the immune system.