Indo-Pacific Finless Porpoises are found mainly in coastal waters, including shallow bays, mangrove swamps, and estuaries. They occur in waters < 200 m deep and can be sighted up to 240 km from shore in some areas. It is uncertain which of the two currently recognized species of Finless Porpoises (possibly both) occurs farther offshore, especially in areas of sympatry.

Indo-Pacific Finless Porpoises appear to have a strong preference for waters with a sandy or soft bottom (Jefferson and Hung 2004).

Small fishes, cephalopods, and crustaceans (mainly demersal species) form the diet of Finless Porpoises (Jefferson and Hung 2004).

Higher numbers of Finless Porpoises are present in Hong Kong waters in winter and spring than in other seasons (Jefferson et al. 2002). Seasonal differences in density and distribution, with higher densities in the winter months of November to January, have been observed along the coast of southern Maharashtra, India, and acoustic monitoring data from there have been interpreted to suggest both seasonal and diurnal patterns of occurrence in near-shore waters (Sule et al. 2017). Minton et al. (2013) also observed a seasonal signal in their vessel surveys in Kuching Bay, with higher densities of Finless Porpoises observed in March, April, and May, which coincided with the occurrence of larger groups containing very small calves. Observations of porpoise behaviour in the bay were interpreted as suggesting that it is an important feeding and calving area (Zulkifli Poh 2013). Two stranded individuals had large shrimp in their stomachs (G. Minton, pers. comm., cited in IWC 2017).

The type specimen was supposed to have come from the Cape of Good Hope, but this location is believed to be erroneous; it is now generally accepted that the type locality is the Malabar coast of India (Rice 1998, Jefferson and Hung 2004).

In general, Indo-Pacific Finless Porpoises occur in a narrow strip of shallow (usually <50 m deep) coastal marine waters (as well as some river mouths and estuaries) around the northern rim of the Indian and western Pacific Oceans from the Persian/Arabian Gulf (Preen 2004, Collins et al. 2005) eastwards around the rim of the Indian Ocean to the Indo-Malay region (Ponnampalam 2012) and to Java, Indonesia (but apparently not the Philippines) and northwards to the Taiwan Strait and central Chinese waters (Gao 1991, Gao and Zhou 1995). This is the more tropical and wide-ranging of the two species of Finless Porpoises. Records of this species from northern Chinese waters (e.g., Wang 1992) probably represent rare or extralimital events. Finless Porpoises are seen regularly (when sea conditions are favourable) in Sarawak, East Malaysia (Minton et al. 2011), in at least parts of Peninsular Malaysia (e.g., they are the most frequently seen cetaceans around the Langkawi Archipelago according to Louisa Ponnampalam (pers. comm. 2017, J.Y. Wang unpublished data)), year-round (but with seasonal influxes) in Hong Kong (Jefferson et al. 2002a), and in parts of the western Taiwan Strait (J.Y. Wang unpub. data). They are also present along the East Kalimantan coastline of Borneo (D. Kreb pers. comm. 2011). In India, they are found in shallow waters along virtually the entire length of both the east and the west coasts, with sightings and strandings more commonly reported on the west coast (Sule et al. 2017). One possible explanation for the difference is that the east coast has only pockets of preferred habitat, while more continuous or contiguous porpoise habitat is available along the west coast (Sule et al. 2017).

Given the paucity of dedicated cetacean survey effort in much of the species’ suspected range, the map includes the possible or projected range where oceanic features are consistent with the species’ known preferred habitat. As such, the species has not been recorded for all the states within the hypothetical range as shown on the map. States for which confirmed records of the species exist are marked as 'Resident' in the list of countries of occurrence. States within the hypothetical range, but for which no confirmed records exist, are included in the list as 'Seasonal Occurrence Uncertain'.

This species (which is presently listed as a single species with N. asiaeorientalis) is included in Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), and in Appendix II of the Convention on Migratory Species (CMS). Management measures are needed to address threats, especially bycatch in fisheries.

At its annual meeting in May 2017 the IWC Scientific Committee’s sub-committee on small cetaceans reviewed the status of Finless Porpoises in India and parts of Malaysia and recommended that populations be surveyed for distribution, abundance, and habitat use with emphasis on areas where the least is known about the species (e.g., India, the Indo-Malay Archipelago, Arabian/Persian Gulf) (IWC 2017). The sub-committee also recommended that bycatch monitoring be improved in all areas of known overlap between Finless Porpoise occurrence and fishing activity, especially gillnetting.