Progress protecting Mekong River dolphins undermined by proposed dams

Somany Phay, Frances Gulland, and H.E. Srun Limsong, Deputy Director General of the Fisheries Administration, Royal Government of Cambodia. Photo Credit: Peter Thomas

In January 2017 an international workshop on the Critically Endangered freshwater population of dolphins (Orcaella brevirostris) in the Mekong River was held in Kratie, Cambodia [click here to read report]. This was the fourth such workshop convened by the World Wide Fund for Nature (WWF) – Cambodia and the Cambodian Fisheries Administration, all of them organized and conducted in collaboration with the CSG and the U.S. Marine Mammal Commission [click here for more details].

At this workshop the external advisory group concluded that significant progress had been made on implementing most of the recommendations from the 2014 workshop, thanks to the commitment of the WWF-Cambodia team, the Fisheries Administration, the River Guards and the local community. The River Guards have worked hard to confiscate gillnets in the core dolphin zones and the consequent reduction in entanglement risk may have been a significant factor contributing to the recent increase in calf survival. The River Guards nevertheless continue to face a number of obstacles and gillnetting remains a serious threat.

River guards burning confiscated gillnets. Photo credit: Peter Thomas

Unfortunately, the threat of hydropower development, addressed in detail at the 2014 workshop, is now a reality for this population. Since the construction of the Don Sahong dam near the Laos/Cambodia border began in 2014, a local subpopulation of dolphins has declined from five to only three individual dolphins and there is now virtually no hope for its persistence. Progress on slowing the decline of the Mekong dolphin population, which currently numbers only about 80 individuals, could

be completely nullified by construction of the proposed Sambor and Stung Treng hydropower dams. If built, these dams will eliminate or transform most of the dolphins’ remaining riverine habitat. A Memorandum of Understanding was signed recently between the Cambodia government and a private company to carry out feasibility studies on the two new dams.

Construction of the Don Sahong Dam on the Mekong River in Laos. Photo Credit: Peter Thomas

Other populations of Irrawaddy dolphins were also discussed, including the Critically Endangered Mahakam (Indonesia) and Ayeyarwady (Myanmar) freshwater ones as well as those in the estuaries and mangrove channels of Bangladesh.

 

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Jan 2017 update on the decline of the Vaquita

As noted in the 16 December 2016 posting on this site, CIRVA (Comité Internacional para la Recuperación de la Vaquita) met in November to update its findings and recommendations concerning vaquita science and conservation. The meeting report, which was officially released today, concludes that the species population has continued its precipitous decline. It numbered only around 30 individuals (95% CRI 8 to 96) by autumn 2016, a decline of nearly 50% since 2015, according to results from the acoustic monitoring program (following the published methodology of Jaramillo-Legorreta et al. 2016 and also Taylor et al. 2016).

Illegal fishing, mainly for totoaba, has continued at alarming levels despite best efforts by the Mexican Government (including the Mexican Navy) in collaboration with the Sea Shepherd Conservation Society. Once again CIRVA stressed, given that the current two-year rangewide ban on gillnets will expire in April 2017, the sale, possession and use of gillnets must be permanently banned in the northern Gulf of California if the vaquita is to survive. Reluctantly, but on the basis of extreme concern over the safety of vaquitas in their natural habitat, the committee also recommended  that the Mexican Government put in place a carefully planned, step-wise attempt to determine whether some vaquitas can be caught and held in a temporary sanctuary until they can be safely returned to a gillnet-free environment (http://www.vaquitacpr.org)​

 

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Progress on Chinese White Dolphin (CWD) Research and Conservation Initiative

The project previously described (see 29 June 2016 news item) has proceeded as planned over the past half-year. A stakeholder workshop organized by Ocean Park Conservation Foundation Hong Kong (OPCFHK) took place in Hong Kong on 10-13 January 2017. More than 55 participants, including fishermen, government officials, scientists, and NGO representatives from mainland China, Hong Kong, Taiwan, and several foreign countries, engaged in discussions aimed at developing a conservation action plan for the humpback dolphins (Sousa chinensis) in the Pearl River Estuary (PRE). This meeting built upon work led by Phil Miller of the Conservation Breeding Specialist Group (CBSG) to produce a Population Viability Analysis. It was organized and chaired by Onnie Byers, Chair of the CBSG.

An adult humpback dolphin surfaces in Hong Kong waters of the Pearl River Estuary. Photo credit: Lindsay Porter

The framework document to be produced from the workshop, which will include a draft action plan, is expected to be available by the end of May 2017 and will be posted on this website. The Airport Authority Hong Kong (AAHK) has been investing in CWD conservation efforts and provided funding for both Miller’s PVA work and the January 2017 workshop. OPCFHK will apply for further funding to support its continuing oversight of implementation of many of the research and conservation actions called for in the action plan. Participation in the workshop by scientists and managers from mainland China was encouraging; their continued engagement will be critical to success.

Action plan implementation is to be guided by the independent Steering Committee consisting of Bob Brownell, Frances Gulland, Phil Hammond (replacing Rohan Currey), Randy Reeves (chair), Wang Ding, and Randy Wells. It should be noted that in addition to the CSG members on the Steering Committee, CSG members Tom Jefferson and Lindsay Porter attended and, very importantly, have been contributing to a collaborative effort led by Wells to combine all available photo-identification material on humpback dolphins in the PRE and make this data set available to all participating CWD researchers, to enable more rigorous population analyses.

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Update on the Vaquita

In June 2016, we reported that the survey conducted in September–December 2015 had shown that only about 60 vaquitas were left (as detailed in the CIRVA-7 report). Despite valiant efforts by the Mexican government and NGOs, it clear that illegal gillnet fishing for totoaba, the primary driver for the vaquita’s dramatic recent decline, continues. The acoustic monitoring program in summer 2016 found that the decline rate has accelerated, making extinction imminent. For more information, see the NOAA Fisheries website.

Also, note that a new CIRVA report (CIRVA-8 in late November 2016) and a new abundance estimate will be released in due course and communicated here on the IUCN/SSC CSG news feed.

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Proposed Live Captures of Cetaceans, Seals and Penguins in Namibia

In March 2016 a proposal to capture African penguins, marine mammals (cetaceans and pinnipeds) and sharks was submitted to the Namibian Ministry of Fisheries and Marine Resources (MFMR) by a partnership of two companies: “Welwitschia Aquatic and Wildlife Scientific Research Pty Ltd” and “Beijing Rare Animal Breeding & Promotion Co”. According to an article in the newspaper The Namibian, the proposed captures would include, annually, “…300 to 500 African penguins; five to 15 killer whales; 50 to 100 common bottlenose dolphins; 50 to 100 Indo-Pacific bottlenose dolphins; 500 to 1 000 Cape fur seals; and various sharks.”

Concern was raised in May 2016 when a Russia-registered ship named the Ryazanovka docked in Lüderitz before moving onto Walvis Bay. The Ryazanovka has been involved in the capture of killer whales in eastern Russia, most recently two killer whales captured in the Magadan region (northern Okhotsk Sea) in 2015. Chinese and Russian parks have been the principal buyers of killer whales captured in the Russian Far East in recent years. According to a recent report by the China Cetacean Alliance, as of October 2015, there were captive cetaceans in at least 36 parks in China, with others under construction. Demand for exotic marine exhibits is clearly high.  The vessel has apparently been sold to local buyers in Namibia (according to the Namibian newspaper Allgemeine Zeitung) and has since been at anchor in Walvis Bay, although a 9 December article suggests the vessel is bunkering and taking on other supplies.

iucn

Namibian conservation groups commented on the proposal soon after it was received. Their concerns included the fact that African penguins are greatly threatened (Endangered on the IUCN Red List) and the scale of the proposed captures would, if successful, deplete, if not eradicate, local populations of bottlenose dolphins and killer whales in a very short period of time.  The most recent abundance estimate of coastal bottlenose dolphins in Namibia is ~100 animals. The proposal attempts to justify the capture of penguins and marine mammals by suggesting this would slow declines in fishery production, an unfounded and widely discredited assumption worldwide. Opposition to the proposal has also been prevalent in the Namibian press, and both national and international NGOs have submitted letters of objection to the MFMR.

The Chair of the IUCN Species Survival Commission submitted a letter (also saved in the CSG Letters page) to the Permanent Secretary of MFMR on 14 October (copied to the Minister and Permanent Secretary of the Ministry of Environment and Tourism). The immediate response from the Permanent Secretary was that a decision had not yet been reached and that the application did not guarantee permission. This was further to assurances that a decision would be made in early October. However as of 14 December no official decision had yet been forthcoming.

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Amazon River dolphins in Brazil continue to be killed for fish bait

It has been known for some time that fishermen have been killing freshwater dolphins in the Amazon and using them as bait for catfish (Mintzer et al. 2013; Iriarte & Marmontel 2013; Brum et al. 2015).  A recent report from Brazil found that following the decline of a regional delicacy, the catfish species called the ‘capaz’ (Pimelodus grosskopfii), fishermen started targeting a different catfish species, known in Brazil as ‘piracatinga’ and in Colombia as ‘mota’ (Calophysus macropterus), that is traditionally disliked by Brazilians because it is a scavenger (Cunha et al. 2015). DNA analysis by Cunha et al. revealed that this fish is being marketed under a variety of fictitious names including ‘douradinha’. River dolphin carcasses provide ideal bait for attracting large numbers of the carrion-feeding piracatinga. Indeed, the presence of dolphin tissue in piracatinga stomachs was confirmed by mtDNA control region sequencing (Cunha et al 2015).

Foetus of an amazon river dolphin being pulled from its mother

Foetus of an Amazon river dolphin being pulled from its mother as she is chopped up for catfish bait. Photo Credit: Alerta Vermelho (www.alertavermelho.org.br)

This use of dolphins as bait is directly linked to dramatic declines in dolphin populations in parts of the Amazon. A 5-year legal moratorium on fishing for piracatinga came into force in Brazil on 1 January 2016. Although the legal text justifying this temporary ban refers to implications for human health (piracatinga have high levels of mercury in their tissues), the trigger for passage of the act was public outrage over the killing of dolphins to supply bait. However, despite the ban, the trade in piracatinga in Brazil continues and therefore dolphins continue to be killed. Observations by scientists studying the dolphins in the central Amazon indicate that enforcement is weak and that the dolphins (and caimans) are still greatly threatened, at least in some large parts of their range.

Brum, S.M., V.M.F. Silva, F. Rossoni and L. Castello. 2015. Use of dolphins and caimans as bait for Calophysus macropterus (Lichtenstein, 1819) (Siluriformes: Pimelodidae) in the Amazon. Journal of Applied Ichthyology 31(4):675-680.

Cunha, H.A., V.M. da Silva, T.E. Santos, S.M. Moreira, N.A. do Carmo and A.M. Solé-Cava. 2015 When you get what you haven’t paid for: molecular identification of “douradinha” fish fillets can help end the illegal use of river dolphins as bait in Brazil. Journal of Heredity 106(S1):565-572.

Iriarte, V. and M. Marmontel. 2013. Insights on the use of dolphins (boto, Inia geoffrensis and tucuxi, Sotalia fluviatilis) for bait in the piracatinga (Calophysus macropterus) fishery in the western Brazilian Amazon. Journal of Cetacean Research and Management 13(2):163-173.

Mintzer, V.J., A.R. Martin, V.M. da Silva, A.B. Barbour and K. Lorenzen and T.K. Frazer. 2013. Effect of illegal harvest on apparent survival of Amazon River dolphins (Inia geoffrensis). Biological Conservation 158:280-286.

 

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Arabian Sea humpback whales are one of only four populations still considered Endangered under the United States revised Endangered Species Act listing.

*This article is a re-post of a recent WWF media release http://wwf.panda.org/wwf_news/?278471/Arabian-Sea-humpback-whales-one-of-only-four-populations-still-considered-endangered-after-lengthy-US-review

Following an extensive review process that started in 2009 and was finalized in September 2016, the United States’ National Oceanic and Atmospheric Administration has revised the status of humpback whale populations around the world under the US Endangered Species Act (ESA).  The modified listing recognizes the Arabian Sea population as one of only four humpback whale populations around the globe that is not recovering from historical whaling, and is at high risk of extinction without serious conservation efforts.

Humpback whale off the coast of the Sultanate of Oman ©Environment Society of Oman

Humpback whale off the coast of the Sultanate of Oman ©Environment Society of Oman

A Biological Review Team examined hundreds of scientific studies and reports that demonstrate how the majority of humpback whale populations around the world are increasing following the International Whaling Commission’s ban on commercial hunting of this species in 1966.  Careful consideration led to the designation of fourteen “Distinct Population Segments” (DPS), nine of which are no longer considered to be in immediate danger of extinction, and have thus been “de-listed”.  A DPS is treated equivalent to a species under the ESA.

However, five populations have not shown the same signs of increase toward recovery, and are still listed as Endangered or Threatened.  Of these, the Arabian Sea population is the smallest, most distinct, and most at risk.  Its range is believed to extend from the coasts of Yemen and Oman in the west to Iran, Pakistan and India in the east.

The notice states: “The Arabian Sea DPS faces unique threats, given that the whales do not migrate, but instead feed and breed in the same, relatively constrained geographic location. Energy exploration and fishing gear entanglements are considered likely to seriously reduce the population’s size and/or growth rate, and disease, vessel collisions, and climate change  are likely to moderately reduce the population’s size or growth rate….. The…. Arabian Sea DPS [is] in the ‘at high risk of extinction’ category.”

 

Map showing the 14 humpback whale Distinct Population Segments (DPS) now recognized under the United States’ Endangered Species Act. Of the four populations that remain Endangered, the Arabian Sea population (number 14 on this map), is considered the most distinct and the most likely to become extinct without conservation intervention. Source: http://www.nmfs.noaa.gov/pr/species/mammals/whales/humpback-whale.html

Map showing the 14 humpback whale Distinct Population Segments (DPS) now recognized under the United States’ Endangered Species Act. Of the four populations that remain Endangered, the Arabian Sea population (number 14 on this map), is considered the most distinct and the most likely to become extinct without conservation intervention. Source: http://www.nmfs.noaa.gov/pr/species/mammals/whales/humpback-whale.html

The Biological Review Team that conducted the 6-year long review process considered evidence from the Arabian Sea that includes information on illegal hunting of whales by Soviet whaling fleets in the 1960’s, fifteen years’ worth of dedicated whale research off the coast of Oman, and a few opportunistic sightings and strandings of whales along the coasts of Pakistan and India.  Data from Oman provide evidence that the population is extremely small, numbering fewer than 100 individuals, and confirm the Soviet whalers’ speculation that Arabian Sea humpback whales comprise the only non-migratory population of humpback whales in the world.  Genetic evidence shows the population to be distinct and no longer in breeding contact with any other humpback whale populations in the Indian Ocean.

These factors, coupled with ever-increasing threats from entanglement in fishing gear, strikes by vessels in some of the world’s busiest shipping lanes, and noise from shipping, coastal development and offshore oil and gas exploration, are cause for serious concern.  The population also has high levels of liver abnormalities and skin disease, which may render them more vulnerable to other diseases or stressors. Furthermore, this non-migratory population, restricted to the “cul de sac” of the Arabian Sea, has no alternative feeding or breeding grounds should climate change or an environmental disaster on the scale of the Deepwater Horizon irrevocably change the dynamics of their limited habitat.

engangled-whale-off-oman-2A humpback whale entangled in a gill net off the coast of Oman (© Environment Society of Oman).

A humpback whale entangled in a gill net off the coast of Oman (© Environment Society of Oman).

While the Endangered Species Act most directly affects whales present within US waters, it also applies on the high seas to any vessels or persons under US jurisdiction.  The notice states that while the International Whaling Commission (IWC) and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) provide significant protections to all large whales, there are no formalized governmental or inter-governmental conservation efforts for the Arabian Sea humpback whale.  To address the lack of coordinated effort to save this population from extinction, whale researchers and conservation organisations from Arabian Sea range states have joined together in the Arabian Sea Whale Network.  Very much a grass-roots initiative, this network strives to support whale research and conservation efforts in the region.  Together with the Wildlife Conservation Society (WCS), The Environment Society of Oman and the US Marine Mammal Commission, WWF has played a critical role in supporting the formation of this network.

Network members in Pakistan, India, Oman and Iran are conducting research to better describe the range and status of the population and working with local stakeholders to mitigate threats, but they lack sufficient funding.  As a result, we know almost nothing about the whales’ current distribution, numbers, or specific habitat needs in their suspected range outside of Oman. Funding is also needed at a regional level to support training and awareness-raising at all levels, and to better coordinate collaborative research and conservation work. Overall, without significant governmental efforts and stakeholder involvement to reduce the threat of whale entanglement in fishing gear along all the coastlines of its range and to address the risk of ship-strike in corridors of high shipping activity, the outlook for the Arabian Sea humpback whale population looks bleak.  Cooperation has been successful in other regions of the world as in the ongoing efforts to conserve gray whales in the western Pacific. Only through collaboration by governments, NGO’s, IGO’s, industry and other relevant stakeholders can we hope to overcome the odds and address the threats to Arabian sea humpback whales.

For more information, contact Arabian Sea Whale Network coordinator Gianna Minton  (gianna.minton@gmail.com) or look at our website:  https://arabianseawhalenetwork.org/

 

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Latest SMM Taxonomy Committee List of Marine Mammal Species Includes Several Species-level Changes

By Thomas A. Jefferson and Patricia Rosel

The Society for Marine Mammalogy’s Committee on Taxonomy publishes a list of marine mammal species of the world and updates it annually.  Recent revisions include many changes at the subspecies level, but here we summarize only species- or genus-level changes.  A ‘new’ whale (actually not new, but a resurrected species), Mesoplodon hotaula, has been added to the list.  The humpback dolphin genus Sousa has been split from two species into four, including the resurrection of S. plumbea (Indian Ocean humpback dolphin), and the addition of a new species, S. sahulensis (Australian humpback dolphin).  Perhaps the most interesting change for many marine mammalogists is the dropping of Delphinus capensis as a recognized species and the resultant lumping of all common dolphins of the world back into the single species D. delphis.  This can be viewed as a provisional change, as work is underway to determine if the eastern North Pacific long-beaked common dolphin, qualifies as a distinct species (or only as a subspecies as it is currently listed).

Some recently proposed species are not on the current list, mostly due to conflicting evidence or the lack of strong evidence for their distinctiveness at the species level.  These include Inia boliviensis, Inia araguaiaensis, and Tursiops australis.   Future work may clarify the status of each of these.  Finally, while it is recognized that several genera of dolphins are paraphyletic or polyphyletic, and thus not good phylogenetic taxa, no taxonomic changes will be made to the list until further work can clarify how best to deal with these ‘problematic’ genera – Lagenorhynchus, Stenella, and Tursiops.

For more details, consult the latest version of the list at: https://www.marinemammalscience.org/species-information/list-marine-mammal-species-subspecies/.  Thanks to Bill Perrin for his many years of service as Taxonomy Committee chair.  Patty Rosel will be taking over from Bill as the new chair.

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Mass mortality event of Black Sea Harbour Porpoises

The subspecies Phocoena phocoena relicta is endemic to the Black Sea and whilst the total population size and trend are unknown, the subspecies is red-listed as Endangered. In recent months, unusually large numbers of neonates and juveniles have washed up on beaches along the Black Sea coasts of Bulgaria and Turkey. The waters there are known to be used by cetaceans for calving and breeding (Dede & Tonay, 2010). Large-scale mortality events have been reported in previous years, but the number of individuals this year has been exceptionally high, with up to 7.2ind./km stranded on the Turkish western Black Sea coast (more than 150 individuals found along a 22km stretch of coastline in July alone). Most were newborn (91%) harbour porpoises (97%), often less than 70cm long. It has been difficult to diagnose cause of death because most of the carcasses were in an advanced stage of decomposition by the time they washed up and were found. The situation in Bulgaria has been similar, with a peak of stranded porpoises, 61-77 cm long, in mid-July, and 6.6ind./km stranded on the Black Sea coast of southern Bulgaria (34 individuals in 3 days along 5.1 km of beach).

Unusual large-scale mortality events were observed in 2003 and 2009 (Tonay et al., 2012) and high mortality of neonates in the summers of 2010 and 2011 was thought to be related to the bottom-set gillnet fishery for turbot (Öztürk et al., 2012). The hypothesis was that lactating and nursing mothers had been caught in nets, resulting in the neonates starving to death and washing ashore. However, whilst this year the strandings seem to be dominated once again by neonates, the number of observed carcasses is much higher than was the case in previous mass mortality events.

Scientists at the University of Istanbul and the Turkish Marine Research Foundation (TUDAV) as well as Dimitar Popov of Green Balkans from Bulgaria, are investigating this year’s mortality event and the causes behind it. For a subspecies that is already considered Endangered, the high mortality of young animals, year after year, could be a serious impediment to recovery.

tudav mass2tudav mass1

tudav_mass4tudav mass3Figure 1. Stranded harbour porpoise neonates in the Black Sea. © TUDAV.

 

References:

Dede, A., Tonay, A. 2010. Cetacean sightings in the western Black Sea in autumn 2007. Journal of Environmental Protection and Ecology 11(4): 1491-1494.

Öztürk, A.A., Tonay, A.M, Raykov, V., Dede, A. 2012. High mortality of harbour porpoise neonates in the southwestern Black Sea in 2010 and 2011. Abstract in proceedings of 26th Annual Conference of the European Cetacean Society, Galway, 90p.

Tonay, A.M., Dede, A., Öztürk, A.A., Ercan, D., Fernández, A. 2012. Unusual mass mortality of cetaceans on the coast of the Turkish Western Black Sea in summer 2009. Journal of the Black Sea/ Mediterranean Environment 18: 65-75.

 

 

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Collaboration on humpback dolphin (Sousa plumbea) research and conservation in South and East Africa

Humpback dolphins in the Indian Ocean were recently recognised as a distinct species (Sousa plumbea) that occurs in coastal waters from South Africa to India (link to earlier news article).  The species occurs in very near-shore habitat, generally in water less than 30 m deep and typically less than 2 km from shore, and is therefore exposed to high levels of human activity throughout its range. The conservation status of all four Sousa species is currently being assessed for the Red List, and S. plumbea has been proposed (but has not yet been listed) as “Endangered”.

Humpback dolphins are considered to be South Africa’s most endangered marine mammals.  They were recently re-assessed for the South African National Red List, and the status was changed from Vulnerable to Endangered due to declining sighting rates and group sizes, in comparison to previous assessments, as well as newly available estimates of abundance from discrete areas that suggest the overall population size in South Africa is very small [1].

In early 2016, a Memorandum of Understanding (MOU) that established the “SouSA Consortium” was signed by 16 scientists and research groups in South Africa.

Figure 1: Some of the signatories of the SouSA Consortium Memorandum of Understanding in South Africa

Figure 1: Some of the signatories of the SouSA Consortium Memorandum of Understanding in South Africa

The consortium is designed to facilitate the collection and sharing of humpback dolphin data across the country, which is hoped to make a substantial contribution towards the conservation of this species.   Specifically, the consortium aims to generate data and analyses on a larger geographical scale, something that is impossible for individual research groups. The specific objectives of the project are to:

  • produce an estimate of the total population size and trend of humpback dolphins in South African waters
  • characterize the movement patterns of humpback dolphins along the entire South African coastline
  • determine spatial and temporal patterns of humpback dolphin distribution and assess connectivity between areas
  • evaluate population viability (incorporating estimates of abundance, reproduction and survival) of humpback dolphins in South Africa.

In Kenya and Tanzania (East Africa), knowledge of humpback dolphins is less extensive than in South Africa, but populations appear to be similarly small and subject to many threats [2]. Funding is secured and plans are in place to sign a MOU to establish an East African Cetacean Working Group that will collaborate on coastal dolphin research and conservation in Kenya and Tanzania.  The East African working group will have similar objectives to the South African SouSA Consortium, and the two groups intend to work together in future to answer broad-scale regional questions related to humpback dolphin conservation.

These types of collaborations are important and to be encouraged in areas where knowledge and resources are limited, but conservation concerns are high, something that is true for many regions and marine mammal species. Fisheries bycatch and the loss of habitat through coastal development are major conservation concerns for coastal small cetaceans that can rarely be addressed adequately by projects working in isolation. Recent reviews of the status of all four species in the genus Sousa (S. teuszii [3]; S. plumbea [2]; S. chinensis [4] and S. sahulensis [5] provide evidence for significant declines in most areas, and much more work is needed to increase scientific knowledge and raise public awareness.

 

References

  1. Plön, S., V.G. Cockcroft, and W.P. Froneman. 2015 Chapter Six – The Natural History and Conservation of Indian Ocean Humpback Dolphins (Sousa plumbea) in South African Waters, in Advances in Marine Biology, T.A. Jefferson and B.E. Curry, Editors, Academic Press. p. 143-162.
  2. Braulik, G.T., K. Findlay, S. Cerchio, and R. Baldwin. 2015 Chapter Five – Assessment of the Conservation Status of the Indian Ocean Humpback Dolphin (Sousa plumbea) Using the IUCN Red List Criteria, in Advances in Marine Biology, T.A. Jefferson and B.E. Curry, Editors, Academic Press. p. 119-141.
  3. Collins, T. 2015 Chapter Three – Re-assessment of the Conservation Status of the Atlantic Humpback Dolphin, Sousa teuszii (Kükenthal, 1892), Using the IUCN Red List Criteria, in Advances in Marine Biology, T.A. Jefferson and B.E. Curry, Editors, Academic Press. p. 47-77.
  4. Jefferson, T.A. and B.D. Smith. 2016 Chapter One – Re-assessment of the Conservation Status of the Indo-Pacific Humpback Dolphin (Sousa chinensis) Using the IUCN Red List Criteria, in Advances in Marine Biology, T.A. Jefferson and B.E. Curry, Editors, Academic Press. p. 1-26.
  5. Parra, G.J. and D. Cagnazzi. 2016 Chapter Seven – Conservation Status of the Australian Humpback Dolphin (Sousa sahulensis) Using the IUCN Red List Criteria, in Advances in Marine Biology, T.A. Jefferson and B.E. Curry, Editors, Academic Press. p. 157-192.

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