Satun-Langkawi Archipelago IMMA

Criterion A – Species or Population Vulnerability

Indo-Pacific humpback dolphins (Sousa chinensis) and Indo-Pacific finless porpoises (Neophocaena phocaenoides) are listed as VU on the IUCN Red List of Threatened Species (Jefferson et al. 2017; Wang and Reeves, 2017), while Irrawaddy dolphins (Orcaella brevirostris) are listed as EN (Minton et al. 2017). However, in Malaysia all three species are listed as Marine Endangered Species and protected under the Fisheries Act 1985 and Fisheries (Control of Endangered Species) Regulation (Amendment) 2008. In Thailand, the three species are all protected under the Wild Animal Reservation and Protection Act, B.E. 2535, and are listed as Endangered on the Thailand Red Data 2017. Research by Ponnampalam et al. (2019) showed that finless porpoises around Langkawi are at highest risk of bycatch from trawl nets and gillnets.

Criterion B: Distribution and Abundance

Sub-criterion B2: Aggregations

Indo-Pacific finless porpoises and Indo-Pacific humpback dolphins have overlapping habitat around the Langkawi archipelago however the latter
species’ distribution is primarily along the eastern part of the Langkawi Archipelago and across to the adjacent Perlis-Kedah mainland coast. Both cetacean species have some of the largest recorded groups known for these species – up to 30 and 204 individuals respectively (Ponnampalam and Jamal Hisne, 2011; Ponnampalam et al. 2014; MareCet, unpublished data). In Satun, Thailand, there appears to be two aggregations of coastal cetaceans segregated to the north and south of Satun respectively. The northern aggregation is mainly comprised of Indo-Pacific humpback dolphins that have a wider distribution as compared to Irrawaddy dolphins that are more confined within a limited area closer to the river mouths. The southern aggregation is mainly comprised of a mix of Irrawaddy dolphins, humpback dolphins and Indo-Pacific finless porpoises (Kittiwattanawong, 2015, 2016, 2017). Estimates of humpback dolphins in Satun are reported to be 29-52 individuals (Cherdsukjai and Kittiwattanawong, 2013). Data available from interview surveys and boat-based surveys indicate that the coastal cetaceans occur year-round in Satun, Thailand.

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

Systematic research by the Marecet Research Organisation amounting 187 survey days across 22 surveys between 2010 – 2018 (11682 km and 895 h of search effort), in the Langkawi Archipelago and adjacent coastal waters, recorded numerous observations of cetacean sightings with calves and a few observations of sexual behaviour (Ponnampalam and Jamal Hisne, 2011; Ponnampalam et al. 2014; MareCet, unpublished data). A total of 34.6% (n = 120) of finless porpoise sightings (N = 347) in Langkawi were of groups containing calves, while 71.2% (n = 99) of humpback dolphin sightings (N = 139) included calves. Irrawaddy dolphin sightings that contained calves made up 55.6% (n = 10) of the species’ total sightings (N = 18) recorded from the mainland coast of Kuala Perlis-Kuala Kedah (MareCet, unpublished data). These suggest the area to be important for the cetaceans’ calving and nursing. In June 2016, a local Langkawi netizen had encountered a dead pregnant finless porpoise whose near-term foetus was found protruding halfway out of the adult animal’s genital opening. A stranded finless porpoise neonate bearing foetal folds was also observed in the area in May 2018 (MareCet, unpublished data). These records imply the occurrence of calving and mating within this IMMA. Groups of humpback dolphins containing neonates made up 7.1% (n = 10) of the species’ total sightings in Langkawi (N = 139). Additionally, humpback dolphins mating or engaging in sexual behaviour were observed in the area and comprised 9.3% (n = 13) of the species’ total sightings (N = 139) (MareCet, unpublished data).

Sub-criterion C2: Feeding Areas

Research by the MareCet Research Organisation amounting to 187 survey days across 22 surveys between 2010 – 2018 (11682 km and 895 h of search effort) in the Langkawi archipelago and adjacent coastal waters recorded numerous observations of cetaceans preying on various types of prey such as marine catfish, garfish and octopus. Finless porpoises recorded as feeding or engaging in probable feeding behaviour constituted 28.8% (n = 100) of the total species’ sightings in Langkawi and adjacent waters (N = 347). This species has been observed feeding on cephalopods, as evidenced by the presence of squid ink during sightings and cephalopod beaks found in the stomach contents of dead stranded animals (MareCet, unpublished data). Humpback dolphins observed feeding or engaging in probable feeding behaviour constituted 56.8% (n = 79) of the total species’ sightings (N = 139), while 50.0% (n = 9) of the total Irrawaddy dolphin sightings (N = 18) were of feeding or probable feeding groups (Ponnampalam and Jamal Hisne, 2011; Ponnampalam et al. 2014; MareCet, unpublished data).