Methods

There is a complex of islands next to Strait of Hormoz, northeastern Persian Gulf (Fig. 1), including Qeshm Island (the largest island in the gulf; area = 1490 km²), Hengam Island (area = 37 km²), Larak Island (area = 49 km²), and Hormoz Island (area = 42 km²). Since 2000, the Environmental Management Office of Qeshm Free Area Organization has conducted a conservation program for sea turtles on the islands. Every year, from March to June, the coasts of the islands were monitored for nesting activities of hawksbill turtles; any stranded sea turtle was also recorded during general patrols along the beaches of the islands. Reports by local people were also considered to find more stranded animals.

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Further, since 2011, patrolling along the coast and coastal waters of Bushehr Province, northern Persian Gulf (Fig. 1) has been organized by the Marine Branch of Bushehr Department of Environment to evaluate the status of sea turtles in the area. In mid-2014, a conservation program was established in Nayband Marine-Coastal National Park using the results of this monitoring process.

The archives of these 2 independent programs were searched to find records of olive ridley turtles along the Iranian coast of the Persian Gulf. Wherever possible, turtles were measured for curved carapace length (CCL) and curved carapace width. All specimens were identified using the characteristics presented by Gasperetti et al. (1993), separating heads, skulls, and carapaces of all turtle species in the area.

All other records of olive ridley turtles in the Persian Gulf reviewed here were cited in peer-reviewed published literature.

Results and Discussion

There are 11 confirmed records of the olive ridley turtle in the Persian Gulf through June 2015; 9 and 2 of these are from Iranian and Arabian coastal waters, respectively. Olive ridley turtles in the Persian Gulf were first recorded by Bishop et al. (2007). On October 2003, the authors found an adult female (presumed based on its 67.5-cm CCL and short tail) entangled in trawl net, as a bycatch in coastal waters of Kuwait. In addition, although without confirmation, Baldwin and Gardner (2005), and Miller et al. (2004) mentioned the probably presence of the species in coastal waters of the United Arab Emirates.

Two carcasses, stranded on Naz Beach (n = 1; autumn 2004; Table 1; Fig. 2c) and Naghasheh Beach (n = 1; autumn 2005; Table 1), southern Qeshm Island (Fig. 1), were, to our knowledge, the first confirmed records of the species from the northern Persian Gulf. The first specimen was presumed to be a subadult based on its 53-cm CCL. The second specimen was decomposed and measurement and sex determination were not possible.

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Table 1. Records of olive ridley turtles, Lepidochelys olivacea, from the Persian Gulf.

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In autumn 2006, one of us (M.H.D.) encountered an olive ridley skeleton used as a decoration in a fisherman’s house in the town of Larak Island. The fisherman claimed that he had collected the specimen from the beach of Larak Island (Fig. 1). However, we cannot be sure about the specimen’s origins.

In December 2007, a dead specimen was collected from a fin-fish wire trap in the coastal waters of Bahrain (Abdulqader and Miller 2012).

In spring 2008, data of a satellite tracking study showed that 2 of 9 tagged olive ridley turtles migrated to Iranian coastal waters in the Persian Gulf after nesting in Masirah Island, located off the east coast of Oman in the Arabian Sea (Rees et al. 2012); both turtles reached the anterior (eastern) part of the Gulf. Rees et al. (2012) also suggested that both of these females avoided summer cooling of northwestern Indian Ocean, caused by the southwestern monsoon and the west Arabian Sea upwelling, by travelling to the entrance of the Persian Gulf.

During the first half of the 2010s, 4 additional specimens were collected from the Gulf’s Iranian coastal waters. Two turtles—both presumed putative subadults—were collected alive from purse-seine nets by local fishermen in coastal waters of the town of Bushehr (n = 1; CCL = 53.5 cm; 10 September 2011; Table 1; Fig. 2d) and Kharg Island (n = 1; CCL = 56.5 cm; 12 February 2013; Table 1; Fig. 2e). Both were tagged and released back to the sea.

Further, a large turtle emerged onto the beach of Nayband Marine-Coastal National Park to nest (Table 1; Fig. 2a–b). The exact location lies near the Gulf of Nayband, northern Persian Gulf (27°17′28.0″N, 52°42′06.1″E; Fig. 1). The nesting activity occurred at 0300 hrs on 16 May 2013 when the turtle emerged onto the beach, constructed a shallow body pit with a depth of about 45 cm, and laid 105 eggs (Fig. 2a). When the nest was checked the following morning, it was discovered that the eggs had been eaten by canids. To the best of our knowledge, this is the first record of olive ridley nesting activity in the Persian Gulf, as well as the most northerly nesting account for the species in the Western Indian Ocean. The rookeries in the Western Indian Ocean, ranking from south to north, are the beaches of South Africa (Hughes 1972), Mozambique, Tanzania (Frazier 1982), Kenya (Church 2004), western India (Sunderraj et al. 2006), Oman (Frazier 1982), and Pakistan (Asrar 1999). The nearest rookeries to the Gulf of Nayband nest site are Hawkes Bay and Sandspit near Karachi, Pakistan, and Masirah Island on the east coast of Oman; these are nonarribada rookeries (Ross and Barwani 1982; Asrar 1999).

The most recent record of olive ridley turtle in the Persian Gulf was for an advanced-decomposed specimen washed ashore on 12 April 2015 at Dustaku Beach, southwestern Qeshm Island (Fig. 1). This individual was assumed to be a subadult based on size (CCL = 62 cm; Table 1; Fig. 2f–g).

Observations of 2 olive ridley turtles in the coastal waters of Kuwait (Bishop et al. 2007) and Bahrain (Abdulqader and Miller 2012) were the only previous reports to our knowledge from the Persian Gulf (Table 1). The first records of olive ridley turtles in Iran were from 3 specimens collected from Guader Bay, eastern Gulf of Oman, in January 1997, although no record was available along Iranian coast in the Persian Gulf (Kami 1997). Hawksbill and green turtles are abundant throughout the Gulf (Price et al. 1993). There are a few records of leatherback and loggerhead turtles in the northern Persian Gulf (Dakhteh 2014). By the records in this publication, the olive ridley turtle became the fifth species of sea turtle in Iranian coastal waters of the Persian Gulf.

The mean CCL of the 6 olive ridley turtles nesting in the Lakshadweep Islands located off the coast of India in the Arabian Sea was 72.8 cm (range, 69–77 cm; Tripathy et al. 2006). Further, the mean CCL of 9 nesting olive ridley turtles measured on Masirah Island in the Arabian Sea was 74.1 cm (range, 71–76 cm; Rees et al. 2012). Another small group (n = 5) of the species nesting in Pakistan had a mean CCL of 69.7 cm (range, 52.5–80 cm; Qureshi 2006). The minimum CCL of 52.5 cm from these reports suggests that the smaller turtles caught in Iranian waters of the Persian Gulf were either small adults or large subadults nearing the end of adolescence (Table 1). In addition, the records of a live olive ridley in October in Kuwait (Bishop et al. 2007), a dead specimen in December in Bahrain (Abdulqader and Miller 2012), 2 individuals that migrated to the Persian Gulf after nesting in March in Masirah Island (Rees et al. 2012), as well as the dates of the new records presented herein (Table 1), suggest that olive ridley turtles are present year-round in the Persian Gulf.

There is no doubt that olive ridley turtles have a very low abundance in the Persian Gulf, but it seems that the presence of the species in this semienclosed harsh marine habitat is higher than previously thought. During 15 yrs (2000 to 2015), 7 olive ridley turtles were recorded by 2 patrolling programs along a small section of the northern Persian Gulf (a complex of islands near the strait and coastal waters of Bushehr Province). Therefore, establishing a communication network among conservation programs and surveying all parts of the area may provide additional records.