Devil ray

Mobula mobular is a ray of the family Mobulidae, in the order Myliobatiformes ^[1]. Recent genetic analyses merge it with Mobula japanica, a name that used to refer to a separate species ^[2]. In Peru it dominated landings of mobulid rays between 2013 and 2023, with 3152 tons, 71.79 % of the total ^[3]. In landings sampled between 2017 and 2019 in Tumbes and Piura, 92.3 % of the 156 specimens measured were juveniles ^[3].

In Peru, the specimens landed measured between 109 and 237 cm in disc width, and most between 145 and 180 cm; the measurements were partly estimated, because large specimens were landed eviscerated and cut in half ^[3]. The sizes at maturity cited are 201.6 cm for males and 236.0 cm for females ^[3].

Telling it apart from other mobulid rays is difficult. According to IMARPE statistics, from 1997 to 2010 the most landed mobulid was Mobula thurstoni and from 2011 to 2015 only the genus Mobula was recorded, whereas other reports name Mobula mobular, formerly called Mobula japanica, as the most landed; the authors note that the discrepancy could result from misidentification because of morphological similarities and the difficulty of recognising animals that are landed butchered ^[4]. The fishers and traders interviewed in Tumbes, Piura and Lambayeque prefer it for its white meat, while that of Mobula thurstoni is pink and that of Mobula birostris and Mobula munkiana is black ^[3].

In the eastern Pacific, the coastal upwelling of northern Peru is among the three most important habitats of the species, because of its high marine productivity ^[4]. Piura and La Libertad are part of the Humboldt Current system, an upwelling zone rich in zooplankton, and the areas with the highest landings of mobulid rays coincide with important habitats of the species ^[3].

Because of the large proportion of immature specimens, 82 % in an earlier study, Tumbes and Piura have been proposed as a nursery area for Mobula mobular ^[3]. The IUCN recognises northern Peru as an Important Shark and Ray Area, because it works as a reproductive zone for the species ^[3].

Mobulid rays grow slowly, mature late and reproduce little, which is why they withstand fishing poorly ^[3]. They are among the elasmobranchs with the lowest rates of population increase ^[4]. For most species of the group, data on age at maturity and fecundity are lacking ^[2].

Of the 156 specimens of Mobula mobular measured between 2017 and 2019, 39 were females, 60 were males and 57 had no sex recorded; there were significantly more males than females ^[3]. All 39 females and 91.7 % of the males (55 specimens) were below the size at maturity ^[3]. A gestation of 1 year has been observed only in Mobula alfredi, and in the other mobulids it is unknown ^[2].

Mobulid rays feed on zooplankton and, at times, on bony fishes when these are abundant; in Mexico and the Philippines, several species, among them Mobula mobular, eat euphausiids that are abundant in certain seasons ^[2].

In Peru, landings of mobulid rays peaked in March, February and December, and the peak for Mobula mobular was in March, at 423.5 tons ^[3]. The authors suggest it could be due to the upwelling of those months, which concentrates food and forms feeding groups that are easier to catch, although the difference between the warm season (December to May) and the cold season (June to November) was not statistically significant for mobulid rays as a whole between 2013 and 2023 ^[3]. With data from 1997 to 2015, by contrast, no significant differences between months were found for the genus as a whole ^[4].

Since 2014, all mobulid rays have been listed in Appendices I and II of the Convention on Migratory Species, and since 2016 in Appendix II of CITES ^[3]. In Peru, CITES Appendix II does not affect the national use of their products, but an export would require conservation measures ^[4].

Since 2016, the only mobulid ray with special protection in Peru was Mobula birostris; in 2024 the government extended protection to all mobulid rays, effective from January 2025, although concerns of fishing communities leave doubts about enforcement ^[3]. Before the national plan of action for elasmobranchs, approved in 2014, there was a rule on the minimum gillnet mesh size, from 20 to 33 cm, for the capture of Mobula and other batoids ^[4].

Between 2000 and 2023, 7444.9 tons of mobulid rays were reported in the small-scale fishery, and in purse seines the average annual landing fell from about 150 tons between 2000 and 2012 to about 37.5 tons between 2013 and 2023, a drop of 75.05 % ^[3]. Gillnets caught 87.23 % of the landings of Mobula mobular between 2013 and 2023 ^[3].

Of the mobulid rays caught with gillnets in northern Peru, 80 % are recovered alive ^[4]. An initial study in New Zealand found a mortality of 50 to 60 % in Mobula mobular released from tuna purse seines ^[2].

In Peru, mobulid ray meat is eaten fresh and dried, and no trade in their gill plates has been seen ^[3]. To dry it, the meat is salted for 24 hours and left in the sun for 3 to 7 days, and about 80 % of the weight of an animal is used as fresh meat ^[3]. The cove of San José, in Lambayeque, has the country's largest salt-drying centre, and the meat is used in dishes such as tortilla de raya, guisado con papas and ceviche ^[3].

Interviewees prefer the meat of Mobula mobular because it is white and tastier, and they pay more for it: on average 2 USD per kilo fresh and 5.1 USD dried, against 1 USD and 3.6 USD for the pink meat of Mobula thurstoni ^[3]. The study interviewed 37 fishers and 21 traders, and 87 % of the fishers used gillnets ^[3]. There are signs of a market for mobulid meat between Peru and Ecuador ^[4].

In Peru it is known mainly from fisheries. From 1997 to 2015, 78.8 % of the landings of the genus Mobula came ashore in the north: Máncora, Zorritos, Cancas, La Cruz and Salaverry ^[4]. According to the fishers of Máncora and Zorritos who were interviewed, the capture zones for Mobula mobular lie off Bocapan, Máncora, Punta Mero and Acapulco ^[3]. From 2013 to 2023, this species made up 73.81 % of mobulid landings in Tumbes and 53.21 % in Piura ^[3].