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.

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.

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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.

 

 

 

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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