{{Short description|Species of mammal}} {{Distinguish|text=the [[Baiji]] (Chinese river dolphin)}} {{Use dmy dates|date=August 2020}} {{More citations needed|date=August 2007}} {{Speciesbox | name = Indo-Pacific humpback dolphin | image = Pink Dolphin.JPG | image_caption = At the theme aquarium in [[Pattaya]], Thailand | status = VU | status_system = IUCN3.1 | status_ref = <ref name=iucn>{{cite iucn |author=Jefferson, T.A.|author2=Smith, B.D.|author3=Braulik, G.T.|author4=Perrin, W.| title = ''Sousa chinensis'' |errata=2018 | volume= 2017 | year = 2017 | doi = 10.2305/IUCN.UK.2017-3.RLTS.T82031425A50372332.en |access-date=21 February 2022}}</ref> | status2 = CITES_A1 | status2_system = CITES | status2_ref = <ref>{{Cite web|title=Appendices {{!}} CITES|url=https://cites.org/eng/app/appendices.php|access-date=2022-01-14|website=cites.org}}</ref> | genus = Sousa | species = chinensis | authority = ([[Pehr Osbeck|Osbeck]], 1765) | range_map = Cetacea range map Pacific Humpback Dolphin.PNG | range_map_caption=Combined ranges of ''Sousa chinensis'' and ''[[Sousa sahulensis]]'' | subdivision_ranks = Subspecies | subdivision = *''S. c. chinensis'' *''S. c. taiwanensis'' }}
The '''Indo-Pacific humpback dolphin''' ('''''Sousa chinensis''''')<ref>{{MSW3 Cetacea| id = 14300082 | page = 732 | heading = ''Sousa chinensis''}}</ref> is a species of [[humpback dolphin]] inhabiting coastal waters of the eastern Indian and western Pacific Oceans.<ref name="Elsevier">{{Citation|last1=Jefferson|first1=Thomas A.|title=Re-assessment of the Conservation Status of the Indo-Pacific Humpback Dolphin (Sousa chinensis) Using the IUCN Red List Criteria|volume=73|year=2016|journal=Advances in Marine Biology|pages=1–26|publisher=Elsevier|isbn=978-0-12-803602-0|last2=Smith|first2=Brian D.|doi=10.1016/bs.amb.2015.04.002|pmid=26790886}}</ref> This species is often referred to as the '''Chinese white dolphin''' in mainland China, Macau, Hong Kong, Singapore and Taiwan as a common name. Some biologists regard the Indo-Pacific dolphin as a [[subspecies]] of the [[Indian Ocean humpback dolphin]] (''S. plumbea'') which ranges from East Africa to India. However, [[DNA testing]] studies have shown that the two are distinct species.<ref name=iucn/> A new species, the [[Australian humpback dolphin]] (''S. sahulensis''), was split off from ''S. chinensis'' and recognized as a distinct species in 2014.<ref name=jeff/> Nevertheless, there are still several unresolved issues in differentiation of the Indian Ocean-type and Indo-Pacific-type humpback dolphins.
==Taxonomy== Two subspecies of the Indo-Pacific humpback dolphin are currently recognized:<ref name="socmammalogy">{{cite web |url=https://www.marinemammalscience.org/species-information/list-marine-mammal-species-subspecies/|title=List of Marine Mammal Species and Subspecies{{!}}May 1, 2022 |date=13 November 2016 |publisher=[[Society for Marine Mammalogy]] |access-date=1 May 2022}}</ref> *''S. c. chinensis'', or the Chinese humpback dolphin *''S. c. taiwanensis'', or the Taiwanese humpback dolphin
== Description == [[File:Sousa chinensis (3) by Zureks.jpg|thumb|Tail with visible grey and pink colours]]
An adult Indo-Pacific humpback dolphin is grey, white or pink<ref name="Jefferson-2008">{{Cite book|last=Jefferson|first=Thomas A.|title=Marine mammals of the world: a comprehensive guide to their identification|date=2008|publisher=Academic|others=Marc A. Webber, Robert L. Pitman|isbn=978-0-08-055784-7|edition=1st|location=London|page=186|oclc=326418543}}</ref> and may appear as an albino dolphin to some. Populations along the coasts of China<ref>{{Cite web|title=Sustainable Seafood|url=https://www.wwf.org.hk/en/oceans/seafood/|access-date=2022-01-11|website=www.wwf.org.hk|language=en}}</ref> and Thailand <ref>{{Cite news|url=https://www.bangkokpost.com/thailand/general/2188347/pink-dolphins-spotted-off-samila-beach|title = Pink dolphins spotted off Samila beach|newspaper = Bangkok Post| date=27 September 2021 | last1=Pakkawan | first1=Assawin }}</ref> have been observed with pink skin. The pink colour originates not from a [[pigment]], but from [[blood vessel]]s which were overdeveloped for [[thermoregulation]]. The body length is {{convert|2|to|3.5|m|abbr=on}} for adults, {{convert|1|m|abbr=on}} for infants. An adult weighs {{convert|150|to|230|kg|abbr=on}}. Indo-Pacific humpback dolphins live up to 40 years,<ref name="Napier" /> as determined by the analysis of their teeth.
Calves are dark grey or black at birth and measure around 1 m (3.3 ft) in length. Their coloration lightens through a mottled grey as they age.<ref name="Jefferson-2008" />
== Behaviour == Indo-Pacific humpback dolphins live in small groups, generally with fewer than ten individuals. They hunt as a group using [[Echolocation (animal)|echolocation]].<ref>{{Cite web|date=2017-05-18|title=Indo-Pacific Hump-Backed Dolphins ~ MarineBio Conservation Society|url=https://www.marinebio.org/species/indo-pacific-hump-backed-dolphins/sousa-chinensis/|access-date=2021-05-25|language=en-US}}</ref>
Adult dolphins come to the water surface to breathe for 20 to 30 seconds before diving deep again, for two to eight minutes. Dolphin calves, with smaller lung capacities, surface twice as often as adults, staying underwater for one to three minutes. Adult dolphins rarely stay under water for more than four minutes. They sometimes leap completely out of the water. They may also rise up vertically from the water, exposing the dorsal half of their bodies. A pair of protruding eyes allows them to see clearly in both air and water.
== Reproduction == {{See also|Dolphin#Reproduction and sexuality}} Female dolphins reach sexual maturity at around ten years old, while males mature at around 13 years old. They usually mate from the end of summer to autumn, and calves are born after a [[gestation period]] of eleven months. The mother stays with her calf until it can find food for itself, usually when it reaches 3–4 years old.<ref name="Napier">{{Cite web|last=Napier|first=Stephanie|title=Sousa chinensis (Indo-Pacific humpbacked dolphin)|url=https://animaldiversity.org/accounts/Sousa_chinensis/|access-date=2021-05-25|website=Animal Diversity Web|language=en}}</ref>
== Threats == The Indo-Pacific humpback dolphin is threatened by habitat loss, water pollution, coastal development, overfishing and an increase in marine traffic within its range.<ref name="BangkokPost">{{Cite news|title=Hong Kong 'risks losing pink dolphins'|work=Bangkok Post|url=https://www.bangkokpost.com/world/348671/hong-kong-risks-losing-pink-dolphins|access-date=2021-05-25}}</ref><ref name="Smith-2015">{{Cite web|last1=Smith|first1=Brian|last2=Braulik|first2=Gillian|last3=Center/NOAA)|first3=Thomas Jefferson (Southwest Fisheries Science|last4=Rla)|first4=William Perrin (IUCN SSC Cetacean|date=2015-06-22|title=IUCN Red List of Threatened Species: Sousa chinensis|url=https://www.iucnredlist.org/en|access-date=2021-05-25|website=IUCN Red List of Threatened Species}}</ref>
In 2015, the Indo-Pacific humpback dolphin was classed as "vulnerable" on the IUCN Red List of Threatened Species.<ref name="Smith-2015" />
=== Water pollution === In 2013, conservationists in Hong Kong warned that the local population had fallen from 158 individuals in 2003 to just 78 in 2011. Members of Hong Kong Dolphinwatch spotted a group of dolphins helping a mother to support her dead calf above the water in an attempt to revive it. A Dolphinwatch spokeswoman claimed that the calf had died after ingesting toxins from polluted seawater through its mother's milk. The [[Hong Kong Dolphin Conservation Society]] warned of a further decline in dolphin numbers in the area.<ref name="BangkokPost" />
=== Plastic pollution ===
Indo-Pacific humpback dolphins are at particular risk of exposure to [[Persistent organic pollutant|organic pollutants]] because they inhabit shallow coastal waters, which are often impacted by human activities. Anthropogenic pollutants pose a risk to marine mammals that reside in coastal waters. Discharge of organic pollutants into marine environments has been shown to decrease water quality, resulting in habitat loss and a significant reduction in [[species richness]].<ref name="Sanganyado-2018">{{Cite journal|doi=10.1016/j.envpol.2018.01.055|title=Bioaccumulation of organic pollutants in Indo-Pacific humpback dolphin: A review on current knowledge and future prospects|year=2018|last1=Sanganyado|first1=Edmond|last2=Rajput|first2=Imran Rashid|last3=Liu|first3=Wenhua|journal=Environmental Pollution|volume=237|pages=111–125|pmid=29477865|bibcode=2018EPoll.237..111S |s2cid=3545603 }}</ref> The loss of key pods has caused species fragmentation, ''also due to habitat loss'', which increases species isolation and decreases connectivity, resulting in population decline.{{Citation needed|date=May 2021}}
[[Plastic pollution]] is widespread across all oceans due to the buoyant and durable properties of plastic, which allow for [[sorption]] of toxicants to plastic while traveling through the environment.<ref>{{Cite journal|last1=Teuten|first1=Emma L.|last2=Rowland|first2=Steven J.|last3=Galloway|first3=Tamara S.|last4=Thompson|first4=Richard C.|date=2007-11-01|title=Potential for Plastics to Transport Hydrophobic Contaminants|journal=Environmental Science & Technology|volume=41|issue=22|pages=7759–7764|doi=10.1021/es071737s|pmid=18075085|issn=0013-936X|bibcode=2007EnST...41.7759T}}</ref><ref name="Eriksen-2014">{{Cite journal|last1=Eriksen|first1=Marcus|last2=Lebreton|first2=Laurent C. M.|last3=Carson|first3=Henry S.|last4=Thiel|first4=Martin|last5=Moore|first5=Charles J.|last6=Borerro|first6=Jose C.|last7=Galgani|first7=Francois|last8=Ryan|first8=Peter G.|last9=Reisser|first9=Julia|date=2014-12-10|title=Plastic Pollution in the World's Oceans: More than 5 Trillion Plastic Pieces Weighing over 250,000 Tons Afloat at Sea|journal=PLOS ONE|volume=9|issue=12|article-number=e111913|doi=10.1371/journal.pone.0111913|issn=1932-6203|pmc=4262196|pmid=25494041|bibcode=2014PLoSO...9k1913E|doi-access=free}}</ref> This has led researchers to the conclusion that [[List of synthetic polymers|synthetic polymers]] are hazardous to marine life and should be declared as a [[hazardous waste]] type. There are many transit paths that allow for plastics and pollutions to enter oceans: freshwater waste can enter oceans by rivers at the delta or estuary, by humans discarding their waste directly into marine waters, or through photo-degradation and other forms of weathering processes that aid in plastic fragmentation and dispersal. Large quantities of fragmented plastics collect in subtropical [[ocean gyre]]s.<ref name="Eriksen-2014" /> Plastic accumulation is not limited to ocean gyres; closed bays, gulfs and seas surrounded by densely populated coastlines and watersheds are all susceptible.<ref>{{Cite journal|last1=Reisser|first1=Julia|last2=Shaw|first2=Jeremy|last3=Wilcox|first3=Chris|last4=Hardesty|first4=Britta Denise|last5=Proietti|first5=Maira|last6=Thums|first6=Michele|last7=Pattiaratchi|first7=Charitha|year=2013|title=Marine plastic pollution in waters around Australia: characteristics, concentrations, and pathways|journal=PLOS ONE|volume=8|issue=11|article-number=e80466|doi=10.1371/journal.pone.0080466|issn=1932-6203|pmc=3842337|pmid=24312224|bibcode=2013PLoSO...880466R|doi-access=free}}</ref>
[[File:Bioakkumulation von schadstoffen.png|thumb|Bioaccumulation: plastic pollutants traveling from lower-trophic levels to higher-trophic levels]]
The consumption of plastics causes adverse effects in marine mammals such as disease susceptibility, reproductive and developmental toxicity.<ref name="Sanganyado-2018" /> Constant absorption of organic pollutants like plastic can be transferred into the dolphin's tissues and organs through an ingestion pathway that is impacting [[megafauna]], lower trophic levels and predators (not limited to Indo-Pacific).<ref>{{Cite journal|last1=Teuten|first1=Emma L.|last2=Saquing|first2=Jovita M.|last3=Knappe|first3=Detlef R. U.|last4=Barlaz|first4=Morton A.|last5=Jonsson|first5=Susanne|last6=Björn|first6=Annika|last7=Rowland|first7=Steven J.|last8=Thompson|first8=Richard C.|last9=Galloway|first9=Tamara S.|last10=Yamashita|first10=Rei|last11=Ochi|first11=Daisuke|date=2009-07-27|title=Transport and release of chemicals from plastics to the environment and to wildlife|journal=Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences|volume=364|issue=1526|pages=2027–2045|doi=10.1098/rstb.2008.0284|issn=1471-2970|pmc=2873017|pmid=19528054}}</ref> Organ toxicity can lead to organ failure, loss of offspring and milk toxicity. Even if the dolphin is not consuming plastic directly then it can take in plastic pollutants through [[biomagnification]] and [[Bioaccumulation of persistent organic pollutants|bioaccumulation]]. Bioaccumulation is defined as the uptake of chemicals from the environment through dietary intake, dermal (skin) absorption or respiratory transport in air or water. This is a huge factor in plastic toxicity consumption in this species due to its long lifespan, which makes it susceptible to chronic exposure. Also, these dolphins contain a large quantity of blubber, ''lipids'', which can result in an excess of toxicity storage in their tissues.{{Citation needed|date=May 2021}}
[[File:Sonar Principle EN.svg|thumb|Echolocation, also known as sonar]]
Plastic pollution can also interfere with dolphins' use of echolocation. [[Animal echolocation|Echolocation]] is the main sense that all dolphins use to navigate, as well as to pinpoint prey and predators.<ref>{{Cite web|title=How do dolphins communicate?|url=https://uk.whales.org/whales-dolphins/how-do-dolphins-communicate/|access-date=2021-05-25|website=Whale & Dolphin Conservation UK|language=en-GB}}</ref> Dolphins and whales use echolocation by bouncing high-pitched clicking sounds off underwater objects, similar to shouting and listening for echoes. The sounds are made by squeezing air through nasal passages near the blowhole. These sound-waves then pass into the forehead, where a big blob of fat called the melon focuses them into a beam.<ref>{{Cite web|url=https://www.discoverwildlife.com/animal-facts/mammals/what-is-echolocation/|title=What is echolocation and which animals use it?|website=Discover Wildlife|language=en|access-date=2019-12-02}}</ref> This process can be interrupted by noise pollution, as well as by obstructions in the water such as masses of oil or plastics.<ref>{{Cite journal|title=Access to University Library Resources {{!}} The University of New Mexico|journal = Environmental Science and Pollution Research International|volume = 25|issue = 20|pages = 19338–19345|doi=10.1007/s11356-018-2208-7|pmid = 29804251|year = 2018|last1 = Nabi|first1 = G.|last2 = McLaughlin|first2 = R. W.|last3 = Hao|first3 = Y.|last4 = Wang|first4 = K.|last5 = Zeng|first5 = X.|last6 = Khan|first6 = S.|last7 = Wang|first7 = D.|s2cid = 44108995}}</ref> Large blockages in the water can refract sound-waves, misleading the dolphin to falsely detect prey, kin or a predator in the area. This can become confusing and frustrating which can lead to extreme stress and potential health issues.{{Citation needed|date=May 2021}}
Clusters of plastic debris can cause noise pollution which interferes with the dolphins' sense of echolocation. As plastic debris is hurled together by ocean currents, sound is produced underwater. An excess of sound waves underwater can render the dolphins' sense of echolocation useless.{{Citation needed|date=May 2021}}
==Distributions and watching== [[File:Chinese white dolphin.jpg|thumb|Adult Chinese white dolphin swimming off the coast of [[Lantau Island]], Hong Kong]]
In Hong Kong, boat trips to visit the Indo-Pacific humpback dolphins have been running since the 1990s.<ref>{{Cite web | url=http://www.hkdolphinwatch.com | title=Hong Kong DolphinWatch Ltd}}</ref> The dolphins mainly live in the waters of [[Lantau]] North, Southeast Lantau, the [[Soko Islands]] and [[Peng Chau]]. A code of conduct regulates dolphin-watching activity in Hong Kong waters.<ref name="Code of Conduct for Dolphin Watching Activities">[http://www.afcd.gov.hk/english/country/cou_vis/cou_vis_mar/cou_vis_mar_mpvs/files/code_of_conduct_dolphin.pdf Code of Conduct for Dolphin Watching Activities, Hong Kong Agricultural and Fisheries Department]. (PDF). Retrieved 2014-05-15.</ref>
There have been some reports of dolphin watching practices that have further endangered the Indo-Pacific humpback dolphins, such as in [[Sanniang Bay]] dolphin sanctuary in [[Qinzhou]]<ref>[http://en.showchina.org/01/01/201104/t893356.htm Show China] {{Webarchive|url=https://web.archive.org/web/20160304022856/http://en.showchina.org/01/01/201104/t893356.htm |date=4 March 2016 }}. En.showchina.org. Retrieved 2014-05-15.</ref> and off [[Xiamen]].<ref>[http://www.v2gg.com/lady/hufumeirong/20140413/159956.html 厦门海之风游艇带您来五缘湾看海豚_厦门海之风游艇有限公微信文章_微儿网]. V2gg.com. Retrieved 2014-05-15.</ref> However, these generally are small, locally organised one-off tours or private pleasure boats that do not adhere to the Hong Kong Agricultural and Fisheries Department's voluntary code of conduct.{{citation needed|date=September 2019}}
[[Nánpēng Islands]] Marine Sanctuary in [[Nan'ao County]] is also home to local pods.<ref>2016. [http://www.xinchaoshang.com/News/Info-42718.html 汕头南澎青罗湾保护区："美人鱼"和精灵们的海域] {{Webarchive|url=https://web.archive.org/web/20170222195246/http://www.xinchaoshang.com/News/Info-42718.html |date=22 February 2017 }}</ref> The population in Leizhou Bay, [[Leizhou Peninsula]], comprising nearly 1,000 animals and the second largest population in the nation, may also be targeted for future tourism.<ref>{{Cite web |url=http://guangdong.kaiwind.com/gdzc/201309/26/t20130926_1117297.shtml |title=近千头中华白海豚栖息广东湛江雷州湾 |access-date=8 February 2017 |archive-url=https://web.archive.org/web/20170211080851/http://guangdong.kaiwind.com/gdzc/201309/26/t20130926_1117297.shtml |archive-date=11 February 2017 }}</ref> [[Hepu National Sanctuary of Dugongs]], and waters around [[Sanya Bay]] and other coasts adjacent on Hainan Island are home to some dolphins.<ref>2016. [http://www.hnfjz.com/about-op-con-gid-182148398614.html 海南海洋生态保护良好，成为大型珍稀海洋动物的"乐园"] {{Webarchive|url=https://web.archive.org/web/20170305201126/http://www.hnfjz.com/about-op-con-gid-182148398614.html |date=5 March 2017 }}. Retrieved 5 March 2017</ref> As the environment and local ecosystems recovery, dolphins' presences in nearby waters have been increasing such as vicinity to the nature sanctuary of [[Weizhou Island|Weizhou]] and [[Xieyang Island]]s.<ref>2014. [http://www.cnwzd.com/news_4298.html 涠洲岛景区现海豚殒命：消息不实] {{Webarchive|url=https://web.archive.org/web/20170307123655/http://www.cnwzd.com/news_4298.html |date=7 March 2017 }}. 中国涠洲岛网. Retrieved 7 March 2017</ref><ref>{{Cite web|title=洱海网|url=https://www.erhainews.com/n4137271.html|access-date=2022-01-11|website=www.erhainews.com}}</ref> [[Gulf of Tonkin]] waters in Vietnam may have unstudied populations that may appear elsewhere such as along [[Xuân Thủy National Park]] and [[Hòn Dáu Island]] in [[Hải Phòng]].<ref>Công An Nhân Dân. 2006. [http://www.vusta.vn/vi/news/Thong-tin-Su-kien-Thanh-tuu-KH-CN/Hai-Phong-Ca-heo-trang-xuat-hien-ca-dan-5293.html# Hải Phòng: Cá heo trắng xuất hiện cả đàn] {{Webarchive|url=https://web.archive.org/web/20170307204744/http://www.vusta.vn/vi/news/Thong-tin-Su-kien-Thanh-tuu-KH-CN/Hai-Phong-Ca-heo-trang-xuat-hien-ca-dan-5293.html |date=7 March 2017 }}. Retrieved 7 March 2017</ref>
[[Cambodia]]: In December 2023, the [[Marine Conservation Cambodia]] (MCC) estimated between 100 and 200 the number of Indo-Pacific humpback dolphins in the region of [[Kampot Province|Kampot]] and [[Koh Kong Province|Koh Kong]].<ref>{{cite web | url=https://www.phnompenhpost.com/national/pink-dolphins-frolic-in-kampot-waters | title=Pink dolphins frolic in Kampot waters }}</ref> During a survey in May of 2024, MCC observed a pod of humpback dolphins with an [[Irrawady dolphin]] mother and calf on the Prek Tnaot River in Kampot.<ref>{{Cite web |last=Phak |first=Seangly |date=2024-05-31 |title=Mixed dolphin pod raises eyebrows |url=https://www.phnompenhpost.com/national/mixed-dolphin-pod-raises-eyebrows |url-status=live |archive-url=https://web.archive.org/web/20240601005733/https://www.phnompenhpost.com/national/mixed-dolphin-pod-raises-eyebrows |archive-date=2024-06-01 |access-date=2024-05-31 |website=www.phnompenhpost.com |language=en}}</ref>
==Taiwanese humpback dolphin== The '''Taiwanese humpback dolphin''' (''S. c. taiwanensis'') is a subspecies of the Indo-Pacific humpback dolphin found in the Eastern [[Taiwan Strait]]. The Indo-Pacific humpback dolphins were first discovered along the west coast of [[Taiwan]] in 2002.{{cn|date=March 2026}} Based on a survey done in 2002 and 2003, they are often found in waters <5m deep, and no evidence shows that they appear in water deeper than 15m.<ref name="iucn-csg.org">Wang, John Y. ''et al''. (eds.) (2007) [http://www.iucn-csg.org/wp-content/uploads/2010/03/2007-Wang-et-al-ETS-Sousa-Conservation-Action-Plan-ENGLISH.pdf Conservation Action Plan for the Eastern Taiwan Strait Population of Indo-Pacific Humpback Dolphins]. National Museum of Marine Biology and Aquarium</ref> A study in 2008 found that the population of humpback dolphins, which occupies a linear range of about 500 km^2 along the central west coast of Taiwan, is genetically distinct from all populations living in other areas.<ref>{{Cite journal|last1=Wang|first1=John Y.|last2=Hung|first2=Samuel K.|last3=Yang|first3=Shih Chu|last4=Jefferson|first4=Thomas A.|last5=Secchi|first5=Eduardo R.|date=2008-12-01|title=Population differences in the pigmentation of Indo-Pacific humpback dolphins, Sousa chinensis, in Chinese waters|journal=Mammalia |url=https://www.degruyter.com/document/doi/10.1515/MAMM.2008.030/html|language=en|volume=72|issue=4|pages=302–308|doi=10.1515/MAMM.2008.030|s2cid=53057721 |issn=1864-1547|url-access=subscription}}</ref> This population is called Eastern [[Taiwan Strait]] population.
Taiwan is a densely populated island and highly developed area, which has many industrial development projects, especially along the west coast, where the Eastern Taiwan Strait populations of Indo-Pacific humpback dolphins live. Based on data collected between 2002 and 2005, the Eastern Taiwan Strait population of humpback dolphins was less than 100 individuals.<ref name="iucn-csg.org"/> The newest data released in 2012 shows that only 62 individuals are left. It means during those 7 years, population of humpback dolphins is being destroyed constantly and severely. A preliminary examination revealed that the Eastern Taiwan Strait humpback dolphin population meets the [[IUCN Red List]] criteria for "[[Critically endangered]]".<ref>Sheehy, D.J. (2009) [http://www.aquabio.com/support-files/impacts-to-sousa-chinensis-from-a-land-reclamation.pdf Potential Impacts to Sousa chinensis from a. Proposed Land Reclamation along the West Coast of Taiwan]. aquabio.com</ref> Without further protection and regulation, this population will go extinct quickly. The Eastern Taiwan Strait is listed as [[Endangered species]] Under the [[Endangered Species Act]] by [[NOAA Fisheries]] since 2018.<ref>{{Cite web|date=2020-12-29|title=Final Rule to List the Taiwanese Humpback Dolphin as Endangered Under the Endangered Species Act |url=https://www.fisheries.noaa.gov/action/final-rule-list-taiwanese-humpback-dolphin-endangered-under-endangered-species-act|access-date=2021-04-04|website=NOAA|language=en}}</ref>
There are several facts that result in the decreasing number of Eastern Taiwan Strait population of humpback dolphins. First, large-scale modification of the shoreline by industrial development including hydraulic filling for creating industrial or science parks, [[seawall]] construction and [[sand mining]] cause [[habitat fragmentation]] and diminish dolphin's habitats. In addition, exploitation of shoreline also contributes to toxic contamination flows into dolphin's habitats. The chemical pollution from industrial or agricultural and municipal discharge results in impaired health of dolphins, for instance, reproductive disorders, and compromised [[immune system]].<ref>Wang, John Y. ''et al''. (eds.) (2004) [http://www.iucn-csg.org/wp-content/uploads/2010/03/2004-Wang-et-al-ETS-Sousa-RESEARCH-ACTION-PLAN-English.pdf Research Action Plan for the Humpback Dolphins of Western Taiwan]. The National Museum of Marine Biology and Aquarium</ref>
Second, fishing activities along the west coast of Taiwan are thriving, and cause many impacts on dolphins. Widespread and intensive use of [[gillnets]] and vessel strikes are potential threats for dolphins. Over exploitation of fish by fisheries' is another threat for the dolphin population. It has led to disturbance of marine [[food web]] or [[trophic level]] and reduces marine biodiversity. Therefore, dolphins have not enough prey to live on.
Still another problem is reduced amount of freshwater flows into [[Estuary|estuaries]] from rivers. Since the Eastern Taiwan Strait population of humpback dolphins is closely associated with estuaries habitat, the elimination of freshwater discharge from rivers significantly decreases the amount of suitable habitats for dolphins.<ref name="iucn-csg.org"/>
[[Hydroacoustics|Hydroacoustic]] disturbance is another critical issue for dolphins. Sources of noise can come from [[dredging]], [[Pile driver|pile driving]], increased vessel traffic, seawall construction, and soil improvement. For all cetaceans, sound is vital for providing information about their environment, communicating with other individuals, and foraging; also, they are very vulnerable and sensitive to the effects of noise. Elevated [[Anthropogenic hazard|anthropogenic]] sound level causes many dysfunctions of their behaviors, and even leads to death.<ref name="iucn-csg.org"/>
In addition to threats from anthropogenic activities, dolphins are potentially at the risk due to the small population size, which may result in [[inbreeding]] and decreased genetic and demographic variability. Finally, [[climate change]] causes more [[typhoon]]s to hit the west coast of Taiwan and cause great disturbance to dolphins' habitats.
John Wang, a professor at Trent University's Biology Department and a researcher at the National Museum of Marine Biology and Aquarium, has been monitoring the species and claims that as of 18 July 2025 there are only 45 to 50 surviving Taiwanese humpback dolphins, with about 60% of those showing signs of injury.<ref> [https://www.cna.com.tw/news/ahel/202507170241.aspx 台灣白海豚僅約50隻 學者：沿岸開發致族群崩解] ''www.cna.com.tw.'' Retrieved 18 July 2025 </ref>
== Conservation ==
The Indo-Pacific humpback dolphin is listed on Appendix II<ref name="Appendices">"[http://www.cms.int/documents/appendix/Appendices_COP9_E.pdf Appendix II] {{webarchive |url=https://web.archive.org/web/20110611112003/http://www.cms.int/documents/appendix/Appendices_COP9_E.pdf |date=11 June 2011 }}" of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005 and 2008. Effective: 5 March 2009.</ref> of the convention on the Conservation of Migratory Species of Wild Animals ([[Bonn Convention|CMS]]). It is listed on Appendix II<ref name="Appendices" /> as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements. In the interim of 2003–2013, the number of these dolphins in the bay around Hong Kong has dwindled from a population of 159 to just 61 individuals, a population decline of 60% in the last decade. The population continues to be further threatened by pollution, vessel collision, overfishing, and underwater noise pollution.<ref>[http://gma.yahoo.com/blogs/abc-blogs/hong-kongs-pink-dolphins-dwindle-just-dozens-151655801.html Hong Kong's Striking Dolphins Dwindle to Just Dozens | ABC News Blogs – Yahoo] {{Webarchive|url=https://web.archive.org/web/20130622043506/http://gma.yahoo.com/blogs/abc-blogs/hong-kongs-pink-dolphins-dwindle-just-dozens-151655801.html |date=22 June 2013 }}. Gma.yahoo.com (21 June 2013). Retrieved 2014-05-15.</ref>
In addition to their natural susceptibility to anthropogenic disturbances, the Chinese white dolphin's late sexual maturity, reduced fecundity, reduced calf survival, and long calving intervals heavily curtails their ability to naturally cope with elevated rates of mortality.<ref>{{Cite journal|last1=Jefferson|first1=Thomas A.|last2=Hung|first2=Samuel K.|title=A Review of the Status of the Indo-Pacific Humpback Dolphin (''Sousa chinensis'') in Chinese Waters|journal=Aquatic Mammals|volume=30|issue=1|pages=149–158|doi=10.1578/am.30.1.2004.149|year=2004 |bibcode=2004AqMam..30..149J }}</ref>
In recent years, Taiwan launched the largest Indo-Pacific Humpbacked Dolphin sanctuary on the Taiwanese coast, stretching from Miaoli County to Chiayi County.<ref>Perrin F.W., Koch C.C., 2007. Wursig B., Thewissen G.M.J, Encyclopedia of Marine Mammals. pp609. Academic Press. Retrieved 13-05-2014</ref> The Indo-Pacific humpback dolphin is also covered by the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MoU<ref>[http://www.pacificcetaceans.org/ Pacific Cetaceans MoU]</ref>).
== Timeline of main events == {{Globalize|Hong Kong|date=November 2011}} * '''1637:''' The Indo-Pacific humpback dolphin was first documented in English by the adventurer [[Peter Mundy]] in Hong Kong near the [[Pearl River (China)|Pearl River]]. The species are attracted to the Pearl River Estuary because of its brackish waters. * '''1765:''' [[Pehr Osbeck]] gives the first scientific description of the species.<ref>Carwardine, Mark (2002) ''Sharks and Whales''. DK ADULT. {{ISBN|0789489902}}. p. 362.</ref> * '''Late 1980s:''' Environmentalists started to pay attention to the Indo-Pacific humpback dolphin population. * '''Early 1990:''' The Hong Kong public started to become aware of the Indo-Pacific humpback dolphin. This was due to the side effects of the construction of the Chek Lap Kok Airport. It was one of the world's largest single reclamation projects: the reclamation of nine square kilometers of the seabed near Northern Lantau, which was one of the major habitats of the dolphins. * '''Early 1993:''' Re-evaluation of the environmental effects of the construction of Chek Lap Kok Airport. This alerted eco-activists such as those from the World Wide Fund for Nature in Hong Kong, in turn bringing media attention on the matter. Soon enough, the Hong Kong Government began getting involved by funding projects to research on the Indo-Pacific humpback dolphins * '''Late 1993:''' The Agriculture, Fisheries and Conservation Department was founded. * '''1996:''' Dr. Thomas Jefferson began to conduct research on the Indo-Pacific humpback dolphins in hope of discovering more about them. * '''1997:''' The Indo-Pacific humpback dolphin became the official mascot of the 1997 sovereignty changing ceremonies in Hong Kong. * '''1998:''' The research results of Dr. Thomas Jefferson was published in "Wildlife Monographs". * '''1998:''' The Hong Kong Dolphinwatch was organized and began to run dolphin watching tours for the general public to raise the public's awareness of the species. * '''2000:''' The Agriculture, Fisheries and Conservation Department started to conduct long-term observation of the Indo-Pacific humpback dolphins in Hong Kong. * '''2000:''' The population of Indo-Pacific humpback dolphins has reached around 80–140 dolphins in the Pearl River waters. * '''2014:''' Jefferson and Rosenbaum revised the taxonomy of the humpback dolphins (''Sousa'' spp.). They describe a new species, the [[Australian humpback dolphin]] and define the accepted common name for this species, the Indo-Pacific humpback dolphin.<ref name=jeff>{{cite journal |first1=Thomas A. |last1=Jefferson |first2=Howard C. |last2=Rosenbaum |year=2014 |title=Taxonomic revision of the humpback dolphins (''Sousa'' spp.), and description of a new species from Australia |journal=Marine Mammal Science |volume=30 |issue=4 |pages=1494–1541|doi=10.1111/mms.12152|bibcode=2014MMamS..30.1494J }}</ref>
==See also== {{Portal|Cetaceans|Mammals|Marine life}} *[[Hong Kong Dolphin Conservation Society]] *[[Wildlife of China]] *[[List of endangered and protected species of China]] *[[List of cetaceans]] *[[Southwest Lantau Marine Park]]
== References == {{Reflist}}
== External links == {{Wikispecies|Sousa chinensis chinensis}} {{Commons category|Sousa chinensis}} *[http://www.afcd.gov.hk/english/conservation/con_mar/con_mar_chi/con_mar_chi_chi/con_mar_chi_chi.html The Agriculture, Fisheries and Conservation Department] *[http://www.hkdolphinwatch.com/ Hong Kong Dolphinwatch] *[https://web.archive.org/web/20061011214012/http://hkdcs.org/ Hong Kong Dolphin Conservation Society] *[https://web.archive.org/web/20120319002035/http://www.cms.int/reports/small_cetaceans/data/S_chinensis/s_chinensis.htm Convention on Migratory Species page on the Indo-Pacific humpback dolphin] *[http://www.pacificcetaceans.org/ Official webpage of the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region ]
{{Cetacea|O.}} {{Taxonbar|from=Q713853}} {{Authority control}}
[[Category:Humpback dolphins]] [[Category:Cetaceans of the Indian Ocean]] [[Category:Biota of Hong Kong]] [[Category:Regional symbols of Hong Kong]] [[Category:Mammals of China]] [[Category:Mammals of Taiwan]] [[Category:Mammals of Southeast Asia]] [[Category:Pearl River Delta]] [[Category:Mammals described in 1765]] [[Category:Taxa named by Pehr Osbeck]] [[Category:Fauna of Timor-Leste]] [[Category:Species that are or were threatened by habitat loss]] [[Category:Species that are or were threatened by pollution]]