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The Indian and western Pacific Oceans (where several of the nesting sites in the southern Pacific Ocean RMU are) are bordered by developing nations whose main livelihoods are dependent on fisheries (Reeves et al. 1988; van der Elst et al. 2005). Both artisanal and commercial fisheries can contribute to abandoned, lost, or discarded fishing gear (hereafter “ghost nets”). Ghost nets can float in the ocean where they can entangle marine animals, with sea turtles being particularly vulnerable (Duncan et al. 2017). This is because ghost nets act as fish aggregators which can attract sea turtles to a potential foraging area (Carr 1987; Chanrachkij & Loog-On 2003; Stelfox et al. 2016). A review of the published and grey literature on the incidents of sea turtle entanglements with ghost nets found that the Indian Ocean was one of the understudied ocean basins (Stelfox et al. 2016).

Here, we report on the incidence of a loggerhead turtle entangled in a ghost net off the coast of Pulau Kendi, an island south of Penang Island on the western coast of Peninsular Malaysia. Although it is possible that there were previous incidents of sea turtles entangled in ghost nets in Malaysia, this is the first reported incident of a loggerhead turtle found in the waters of Peninsular Malaysia entangled in a ghost net.

Penang Island is on the west coast of Peninsular Malaysia with the Indian Ocean and the Straits of Malacca to the west and south, respectively (Fig. 1). Its oceanography is largely driven by the monsoon. Currents flow east from the Indian Ocean into the Straits of Malacca during the southwest monsoon between May and August and reverse during the northeast monsoon between November and February (Shankar et al. 2002; <http://www.met.gov.my/pendidikan/cuaca/fenomenacuaca>).

Figure 1. Location of Penang Island (red star), Malaysia (yellow polygon) relative to the Indian Ocean and the Straits of Malacca (inset), as well as the sites (stars) where the loggerhead turtle was encountered (blue), released (pink), and rehabilitated (green).

On 7 September 2019, the loggerhead turtle was found with its head and front flippers entangled in a discarded trawler net by three inshore fishermen of Teluk Kumbar approximately 500 m from Pulau Kendi (5.2345 °N, 100.1915 °E, Fig. 1), south of Penang Island. The 2×3 m net had two different mesh sizes: 20 cm on one half of the net and 10 cm on the other. The fishermen cut the net to release the turtle (Fig. 2), but found it was too weak to swim and simply floated adrift. The fishermen brought the sea turtle to shore after they notified the head of the Teluk Kumbar Fishermen Unit, who later alerted the Department of Fisheries.

The sea turtle was transported to the Tunku Abdul Rahman Aquarium in Batu Maung for rehabilitation (Fig. 2). At the time of rescue, it weighed 60 kg with 82 cm curved carapace length and 75 cm curved carapace width. Its diet in the aquarium mainly consisted of mackerel. Based on morphology and genetic assessment conducted by the Fisheries Research Institute at Batu Maung, Malaysia, the sea turtle was confirmed to be a loggerhead turtle. However, analyses to trace the origin of the turtle were not conducted. It was released seven weeks later at Pasir Belanda, Penang Island, into the bay of Teluk Kumbar (Fig. 1), on 24 October 2019 after it displayed good health and was swimming actively within its holding tank (Fig. 2). This site is a known nesting area for other sea turtle species (Mohd Salleh et al. 2012) and was believed to be a suitable release site for this individual.

Figure 2. Left panel: the loggerhead turtle was brought onto the boat and transported to shore for (center panel) rehabilitation before (right panel) being released to the sea.

It is not known when or where the individual was entangled before it was found. The southwest and southeast Indian Ocean RMUs are a possibility due to their proximity to the Straits of Malacca (Wallace et al. 2010), which include Myanmar (Thorbjarnarson et al. 2000), the Javan Sea near the Sunda Straits (Manansang et al. 1995), and Western Australia (Riskas 2014). It is also possible that the loggerhead turtle may have come from the southern Pacific Ocean RMU (Wallace et al. 2010), such as the seas south of Sulawesi (Manansang et al. 1995).

The origins listed above are namely the nesting beaches for loggerhead turtles (Wallace et al. 2010). Because nesting beaches tend to be great distances away from foraging areas, it is likely that its foraging areas could be even closer to where this individual loggerhead turtle was found. A nesting loggerhead turtle satellite tagged in Taiwan was found to migrate to the South China Sea on the east coast of Peninsular Malaysia (Kobayashi et al. 2011). This points to the possibility that there could be a foraging area for loggerheads on the east coast of Peninsular Malaysia. Given that the loggerhead turtle in Penang did not have heavy barnacle load nor was in poor body condition, there is a possibility that it may have been within an undiscovered foraging area for loggerhead turtles within the Straits of Malacca before it was entangled and encountered.

Managing ghost nets in faraway seas can be impossible, but doing so locally is easier. The origin of this loggerhead sea turtle is not known, but the possibility that it was foraging within the Straits of Malacca before it became entangled in a ghost net cannot be discounted. While the possibility of a new foraging site for loggerhead sea turtles in Malaysia can spur the proper management of ghost nets in Malaysia, ghost nets are a threat to many other marine species, and should be managed regardless. In December 2020, there was an incidence of a loggerhead turtle carcass washed ashore on Langkawi Island. This island is located to the north of Penang Island and is in close proximity to the Andaman Sea. It is possible that there is an unknown foraging ground not just within but beyond the Straits of Malacca that needs to be protected.

Acknowledgements. The authors acknowledge the staff of Tunku Abdul Rahman Aquarium where the loggerhead turtle was rehabilitated; Norhidayah Nadila Maulad Daud for getting the details on the net and sea turtle when found; Nicolas Pilcher, Nurul Salmi Abdul Latip, Mohd Uzair Rusli and Eva Horcajo-Berná from the Society for Conservation Biology - Malaysia Chapter as well as Jillian Hudgins from the Olive Ridley Project for their feedback and comments on the manuscript; and Surin Suksuwan for providing references.

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