Leatherback

Dermochelys coriacea is the only living species of the family Dermochelyidae and was described by Vandelli in 1761 ^[1],[2]. In Peru it is called «tortuga dorso de cuero», «tortuga laúd» or «tinglada» ^[2]. No other sea turtle reaches its size: it can measure up to 3 metres ^[3]. No nests are known from Peruvian beaches, but it visits the coast to feed, mostly on jellyfish ^[2]. The 2013 global assessment of the IUCN Red List lists it as Vulnerable ^[4], and Peru's official list of threatened wildlife of 2014 classifies it as Endangered ^[5].

The species was described in 1761 as Testudo coriacea, from an animal caught at Ostia which Pope Clement XIII donated to the University of Padua ^[2]. In 1816 the French zoologist Henri Blainville erected the genus Dermochelys, and in 1843 Leopold Fitzinger placed the genus in a family of its own, Dermochelyidae ^[2]. Its common name refers to the leathery texture of its shell ^[2].

Unlike all other sea turtles it has neither scales nor a hard shell: its back is made of small interlocking bones covered by thick, rubbery skin, and 7 lengthwise ridges run along it before tapering to a blunt point ^[6]. The skin is mostly black, with a pinkish white underside ^[6].

The front flippers are proportionally longer than in other sea turtles and the hind ones are paddle-shaped ^[6]. Adults usually measure 5 to 6 feet (about 1,5 to 1,8 m) and weigh between 750 and 1000 pounds ^[6]. It has no crushing beak; instead it has pointed, tooth-like cusps, sharp-edged jaws and backward-pointing spines in the mouth and throat that help it hold on to gelatinous prey ^[6].

It occurs in every ocean, nesting on tropical beaches and feeding as far as temperate and subpolar latitudes ^[3]. The eastern Pacific subpopulation nests on the coasts of Mexico, Central America and South America, and ranges from Baja California Sur, in Mexico, to central Chile ^[3].

In Peru it has been documented in both coastal and oceanic waters, with an important aggregation off La Libertad ^[2]. An observer programme aboard artisanal boats from Salaverry recorded it mostly between 8° and 9° S and between 79° and 81° W ^[2]. There are records of catches, landings and strandings in Tumbes, Salaverry, San Andrés in Ica, and Morro Sama in Tacna; off Pisco it has been most frequent between December and March ^[2].

In northern Peru, a habitat model built from the sightings that fishers from Máncora and Cancas marked on maps during interviews in 2019 found that distance to the 200 m isobath was the variable that best explained where the species was seen ^[7].

There are no nesting records on Peruvian beaches; the turtles that reach Peru belong mainly to the eastern Pacific population, whose main nesting beaches are in Costa Rica, in the Las Baulas protected area, and on the Pacific coast of Mexico ^[2]. A female carrying mature eggs was found at the port of Chimbote ^[2].

Females nest at night and return to do so every 2 to 4 years; within a season they lay several times, usually 8 to 12 days apart, clutches of about 100 eggs that take roughly 2 months to hatch ^[6]. Maturity is estimated at between 9 and 20 years of age, and lifespan at 45 to 50 years or more ^[6]. It can dive to about 4000 feet (about 1200 m), deeper than any other turtle, and stay under for up to 85 minutes ^[6].

At the port of Pucusana 115 animals were measured, with a mean carapace length of 135 cm (112 to 168 cm); taking 130 cm as the size at maturity, 71 % were adults ^[2]. By contrast, the 13 carapaces of this species that IMARPE identified in the rubbish dumps of Pisco between November 2009 and March 2015 had a mean curved length of 113 cm, and 70 % belonged to juveniles or pre-adults ^[2].

Its migrations are among the longest of any sea turtle ^[6]. Of 46 females fitted with satellite transmitters at Playa Grande, Costa Rica, between 2004 and 2007, the mean track followed was 8070 km: once nesting was over they swam south along the same route every year, passed through the equatorial region and reached the South Pacific Gyre ^[8].

Off Peru it feeds mainly on the jellyfish Chrysaora plocamia ^[2]. During the 1987 El Niño, the stomach contents of one animal were 100 % that jellyfish, and in another study, 2 more stomachs held unidentified coelenterates, the kelp Macrocystis pyrifera and plastic bags ^[2].

Between 2010 and 2014, the yearly occurrence of the species off Peru closely tracked the abundance of Chrysaora plocamia, with a correlation coefficient of 0,935, and the highest concentrations were off Pisco, at 14° S, and off San José, at 06°30' S ^[2].

In northern Peru, eastern Pacific adults arrive mainly in the austral summer, from November to May, from nesting beaches in southern Mexico, Costa Rica and Nicaragua to eat jellyfish, while juveniles may be present all year ^[7].

Its global category on the IUCN Red List is Vulnerable ^[4]. In Peru it is classified as Endangered ^[5].

The decline in the eastern Pacific has been severe: according to the regional action plan of the Laúd OPO network, cited in the national plan, the population has fallen by more than 90 % since 1980, and over 3 generations it went from more than 35000 nests a year to fewer than 1000 ^[2].

Bycatch in artisanal fisheries is a known threat in Peru. A study published in 2007 brought together two sets of records of leatherbacks accidentally entangled or hooked along the coast: 33 noted opportunistically from 1985 to 1999 and 133 documented by dockside observers from 2000 to 2003, in coastal gillnets and longlines of the dolphinfish, shark and ray fisheries ^[9]. In the fishing coves of San Andrés, Tambo de Mora and Cerro Azul, fishers surveyed in 2012 placed most interactions in inshore set nets for rays, guitarfish, smoothhounds and mullets, and in oceanic drift nets for sharks, manta rays and dolphinfish ^[2].

In the north of the country, the 2019 participatory risk analysis identified gillnets, both surface and bottom, as the riskiest gear for the species, followed by bottom longlines, while handlines carried the lowest risk; the highest-risk zones were concentrated between Cancas and El Alto ^[7].

Peru is party to the Inter-American Convention for the Protection and Conservation of Sea Turtles, whose parties committed in 2015 to conserving the eastern Pacific population of this species ^[3]. Peru's National Plan for the Conservation of Sea Turtles covers the period 2019-2029 ^[2].

In surveys held in 2012, older fishers from Tambo de Mora and Jahuay recalled that they used to harpoon leatherbacks, looking for them where the jellyfish Chrysaora plocamia, their food, gathered ^[2].

In interviews held in 2019 with 85 fishers from Máncora and Cancas, 67 said they had seen a leatherback at some point, and 76 % (n = 51) considered the species important for the ocean ^[7].

The coastal waters off Salaverry, in La Libertad, have been identified as an important feeding area, and the waters off Pisco and Chincha are another relevant zone ^[2]. In the north, the model built from the sightings marked by fishers from Máncora and Cancas in 2019 placed the most suitable habitat within 200 m depth, including the Banco de Máncora, although the authors warn of possible sampling bias ^[7].

In Tumbes, observers aboard coastal gillnet boats between 2017 and 2019 recorded no catches of this species; the authors warn that they made only 3 trips in waters deeper than 200 m and that this may underestimate species with a more oceanic distribution, such as the leatherback ^[10].