Threatened and Endangered

The Most-Endangered Cetacean Species

Thomas A. Jefferson, Ph.D., Visiting Scientist at the Southwest Fisheries Science Center in La Jolla, CA

Cetaceans have long been highly prized by humans looking for a good source of food, oil and a whole host of other products. Cetaceans are attractive subjects for human exploitation because of their enormous size. Until the last few hundred years, their relatively inaccessible habitats made them difficult to hunt. Although there is evidence that prehistoric humans may have taken advantage of the fortuitous stranding of a fresh whale or dolphin on their shores, most cetacean species were relatively safe from large-scale human exploitation until recently.

The first known large-scale hunting of whales was by the Basques, starting in the first millennium AD. They hunted in the Bay of Biscay bounded on the east by the west coast of France and on the south by the north coast of Spain. They mainly targeted the North Atlantic right whale (Eubalaena glacialis), and were so effective in killing so many of this species that their recovery is in doubt today. Norse and Icelandic whalers also hunted in the North Atlantic, and the Japanese began their culture of whale hunting in the 1600s. In the 1700s, the “Yankee whaling” era began, focusing largely on sperm whales (Physeter macrocephalus). This led to the United States becoming a major player in the commercial whaling game. In the late 1800s, the development of steam-powered vessels and the exploding harpoon ushered in the modern era of commercial whaling. Fast-swimming Balaenoptera species, such as the rorquals (blue, fin, sei, Bryde’s and minke whales) were now within the realm of commercial whalers. It did not take long for whalers to decimate species after species, starting with the largest and working their way down the list, to “commercial extinction” (the point at which it is no longer financially viable to continue the hunt).

However, the public perception that all large whales are endangered is wrong. The truth is that most large whales are no longer commercially hunted and many are recovering from past exploitation—with major exceptions being the North Atlantic and North Pacific right whale (E. japonica) species. The real serious conservation problems now lie with several of the smaller cetacean species. The vaquita (Phocoena sinus), Indus susu (Platanista gangetica minor), North Island Hector’s dolphin (Cephalorhynchus hectori maui) and Atlantic humpback dolphin (Sousa teuszii) are some of the most severely endangered species.

In recent decades, the direct killing of whales and dolphins has become much less important, and the indirect deaths of dolphins and porpoises in particular have increased dramatically. There is now no doubt that more cetaceans die incidentally in fishing nets each year than from any other threat, including whale and dolphin hunting.

In the last few decades, we have also seen the development of other major threats to these animals in the form of habitat degradation, environmental contamination, noise pollution (including naval sonars), and even live captures for captive display and research. Despite a number of populations of cetaceans in specific regions being annihilated by humans (e.g., the Atlantic gray whale by commercial whaling), it is only recently that an entire cetacean species has gone extinct at the hands of humans. However, several other species, such as the vaquita in Mexico and Northern Hemisphere right whales, are now on the verge of that same fate.

The baiji, found only in the Yangtze River and some connected lakes in China, was declared to be probably extinct in 2007, after an extensive survey of nearly their entire known range turned up no sightings or acoustic detections. Besides incidental deaths in fishing gear and problems of severe pollution, the baiji suffered from general habitat loss and degradation. Their environment was severely degraded from rapid modification of the river for human use, with little or no concern for its original inhabitants. The Chinese Government had been warned of this for decades and ignored the pleas of the outside world.

The vaquita porpoise leads a precarious existence in the northern Gulf of California, Mexico. This small porpoise species is declining due to being caught as incidental bycatch in gillnets.

A 2015 survey estimated the vaquitas at about 60 individuals. In 2018, the population is estimated at less than 30 individuals.  The Mexican government has taken the situation seriously, and in June 2017, they announced a permanent ban on gillnets in the vaquita’s range. Although they are still dying in illegal gillnets, set to catch another endangered species, the totoaba fish. The totoaba  swim bladder commands extraordinarily high prices (sold for as much as $10,000 on the black market, according to a report from the Environmental Investigation Agency). It is sold in Asia as a coveted aphrodisiac and used for ailments from liver disease to arthritis. The vaquita is in serious trouble and the gillnet ban is essential for the vaquita to survive in its natural habitat and is what scientist and conservation organizations have been requesting for many years.

One thing that is important to remember about endangered species is that some “Endangered Species Lists” include species mainly for political reasons, and their legal status listing may not be accurate. Thus, there is a difference between Endangered (the official status listing, with a capital E) and endangered (the true status of a species, with a lower-case e). For example, the sperm whale is listed as Vulnerable by the International Union for the Conservation of Nature (IUCN) and Endangered by the US Government, yet it is globally distributed, numbers in the hundreds of thousands and many populations are quite healthy. Thus, the sperm whale is not really endangered.

Nonetheless, several cetacean species, and many other populations, are genuinely in danger of extinction in the next decade or two. This is a sad statement on the depths of human greed and carelessness for the natural environment. It is my hope that this article will help people appreciate the diversity and fragility of the world’s marine mammals, and will inspire them to work towards their long-term protection.

Clarifying endangered isolated populations vs. entire species, a quote from Dr. Jefferson:

"The gray, sei, blue, and fin whale species are not endangered on a global scale, but isolated populations of these species have been severely depleted and face some danger of extinction. Sadly, there have probably been several cetacean populations that have been exterminated by humans before they were even documented by scientists. In fact, even today for most species of cetaceans, global population structure is very poorly known."

For additional reading about Endangered Species of Cetaceans:

JEFFERSON, T. A., M. A. WEBBER and R. L. PITMAN. 2015. Marine Mammals of the World: A Comprehensive Guide to Their Identification – 2nd Edition. Academic Press/Elsevier, 616 pp.

REEVES, R. R., B. D. SMITH, E. A. CRESPO and G. NOTARBARTOLO DI SCIARA. 2003. Dolphins, Whales and Porpoises: 2002-2010 Conservation Action Plan for the World's Cetaceans. IUCN - The World Conservation Union, 139 pp.

REEVES, R. R. 2009. Conservation efforts. Pp. 275-289 in Encyclopedia of Marine Mammals (Second Edition) (W. F. Perrin, B. Würsig and J. G. M. Thewissen). Academic Press.

SCHIPPER, J., and many, many others. 2008. The status of the World's land and marine mammals: Diversity, threat, and knowledge. Science 322:225-230.

TURVEY, S. T., R. L. PITMAN, B. L. TAYLOR, J. BARLOW, T. AKAMATSU, L. A. BARRETT, X. ZHAO, R. R. REEVES, B. S. STEWART, K. WANG, Z. WEI, Z. ZHANG, L. T. PUSSER, M. RICHLEN, J. R. BANDON and D. WANG. 2007. First human-caused extinction of a cetacean species. Biology Letters 3:537-540.

ISAAC, N. J. B., S. T. TURVEY, B. COLLEN, C. WATERMAN and J. E. M. BAILLIE. 2007. Mammals on the EDGE: Conservation priorities based on threat and phylogeny. PLoS ONE 2:published online (doi:10.1371/journal.pone0000296).

TURVEY, S. 2008. Witness to Extinction: How We Failed to Save the Yangtze River Dolphin. Oxford University Press, 234 pp.

To learn more about Endangered Cetaceans through the Internet visit:

• NOAA Fisheries Office of Protected Resources
  www.nmfs.noaa.gov
• Whale and Dolphin Conservation Society
  www.wdcs.org
• American Cetacean Group
  www.acsonline.org
• Save The Whales
  savethewhales.org

Irrawaddy Dolphins Disappearing from the Mekong River

Isabel L. Beasley, Ph.D.

As a result of intense competition with humans for freshwater resources, freshwater Irrawaddy dolphin populations are some of the most endangered of all cetacean species. Irrawaddy dolphins, Orcaella brevirostris are found in localized coastal/estuarine regions around Southeast Asia, with riverine populations in the Mahakam (Indonesia), Ayeyarwady (Myanmar) and Mekong (southern Laos, Cambodia and Vietnam) River systems. The Irrawaddy dolphin subpopulation in the Mekong River (hereafter referred to as the “Mekong dolphin population”) was classified as “Critically Endangered” by the World Conservation Union (IUCN) in 2004, and is thought to be declining rapidly.

The Mekong dolphin population is now restricted to the upper 190km (190km = 118.06 miles) of the Cambodian Mekong River, from Kratie north to the Laos/Cambodian border. Photo-identification studies have shown that the total population was an estimated 127 individuals in 2005, as may now be as few as 86 individuals. The main problems facing the population are unsustainable newborn mortalities; accidental gillnet entanglement; and dolphin-watching tourism.

During dedicated studies conducted from 2001-2005, only two calves were known to survive past the first few weeks of life (these two calves were born in January 2004 and were still alive as of April 2005); all other newborns observed in the river were found dead within weeks of being sighted. These unsustainable newborn mortalities have continued in recent years, with 16 newborns found dead in 2006 and nine in 2007. WWF-Cambodia now have a dedicated Mekong dolphin veterinary program in an attempt to determine cause of death, however no definitive answers have yet been found.

As with many cetacean populations gillnet entanglement is a known problem, and has contributed to at least half the known adult mortalities. In 2005, the Cambodian Government decreed that the Kratie to Lao/Cambodian border river stretch would be a gill-net free area, in a well-intentioned attempt to conserve the remaining dolphin population from a major source of anthropogenic mortality. Unfortunately, there was no prior consultation with the local communities along the river, who commonly use gillnets for subsistence fishing. Additionally, no alternative livelihoods were provided (except independently by a local Cambodian NGO in only two villages), or gear modification trials conducted, before this legislation came into effect. These well-enforced initiatives have inevitably alienated the local people, despite the communities’ positive perceptions towards dolphins and demonstrated willingness to participate in small-scale management efforts previously initiated by dolphin conservationists.

Dolphin-watching tourism occurs in two areas of the river, and based on results of other dolphin-watching studies around the world are no doubt having significant impacts on targeted populations. Irrawaddy dolphins inhabit the same small deep-water pools for most of their lives (some pools no larger than 2km x 2km, 2km = 1.24 miles). The noise and harassment from daily dolphin-watching tourism in small motorised boats affects all dolphins inhabiting the small, confined pools, and may be one of the factors responsible for the high newborn mortality. As an example, In Kampi Pool near Kratie Township, there are at least 20 small boats operating in the 1 km x 1 km (1km = 0.62 miles) pool during the dry season. There is minimal management of this tourism; no educational/awareness information provided to tourists; no benefit to the targeted dolphin groups; and despite outside appearances, very little revenue goes back to the local community. An international awareness campaign is therefore planned to encourage international and national tourists to view the dolphins from land (easily viewed during the dry season), rather than hiring boats to view them.

Additional large-scale conservation concerns for the Mekong dolphin population result from various sources of habitat degradation (e.g., large scale dam construction; contaminants from industry and agriculture; and conversion of natural habitat to farmland), disease, reduced prey, and loss of genetic diversity. Even with the most comprehensive management plan accepted by all stakeholders, dolphins will not survive in the river if adequate habitat is not available. Dolphins rely on deep-water areas during the dry season and annual fish migrations to replenish fish stocks. The construction of dams along the mainstream lower Mekong River (particularly southern Laos or Cambodia), will no doubt substantially increase the risk of the Mekong dolphin population’s extinction.

On a more positive note, dedicated efforts to conserve the remaining population are continuing by WWF-Cambodia, with recent assistance and advice from the IUCN Cetacean Specialist Group and associated researchers. If it is not already too late to conserve the remaining dolphin population, with effective in-situ conservation and management, Irrawaddy dolphins could serve as a flagship species for conservation of the Cambodian Mekong River stretch from Kratie to the Lao/Cambodia border, which is a biologically diverse, highly important ecosystem for a number of endangered flora and fauna species.