Cephalorhynchus hectori ssp. maui

– Critically Endangered

Taxonomy

Kingdom:

ANIMALIA

Phylum:

CHORDATA

Class:

MAMMALIA

Order:

CETACEA

Family:

DELPHINIDAE

Scientific Name:

Cephalorhynchus hectori ssp. maui

Infra-specific Authority:

Baker, Smith & Pichler, 2002

Synonym/s:

Cephalorhynchus hectori (van Beneden, 1881) (North Island subpopulation)

Common Name/s:

English

—

MAUI'S DOLPHIN, NORTH ISLAND HECTOR'S DOLPHIN

Taxonomic Notes:

Baker et al. (2002) described the subspecies Cephalorhynchus hectori maui from the North Island of New Zealand based on morphological and genetic evidence. The nominal subspecies is restricted to the South Island. This taxon was previoulsy treated on the IUCN Red List as the North Island subpopulation of C. hectori.

Assessment Information

Red List Category & Criteria:	CR C1, D ver 2.3 (1994)
Year Assessed:	2000
Assessor/s:	Slooten, L. & Taylor, B.L. (Cetacean Specialist Group)
Evaluator/s:	Reeves, R. & Taylor, B.L. (Cetacean Red List Authority)
Justification:	The population of Maui's Dolphin could plausibly number fewer than 100 individuals. An age structured model (Slooten et al. 2000) indicates that approximately 50% of Hector’s Dolphins are mature individuals. Therefore, it is likely that there are fewer than 50 mature individuals, thus qualifying this subpopulation as Critically Endangered (criterion D). The population clearly numbers fewer than 250 mature individuals, with a continuing decline over two generations greater than 20% (criterion C1). Using the model described in Martien et al. (1999) the estimated decline over two generations (26 years) is 61-76% for the Maui's Dolphin population, with the range covering uncertainty in population growth rate

Geographic Range

Range Description:	Hector's Dolphin is endemic to New Zealand waters. The North Island subspecies (Maui's Dolphin) is restricted to the west coast of the North Island of New Zealand, between Dargaville and Kawhia (Dawson and Slooten 1988, Russell 1999). Previous sightings off the east coast of the North Island (e.g., Russell 1999) mean that either there used to be a much larger contiguous population or that a separate subpopulation on the North Island has already been lost. Studies of mitochondrial and nuclear DNA show that Maui's dolphins are genetically distinct from any of the South Island populations (Pichler et al. 1998). Every sampled individual (n = 11) in the contemporary North Island population has a single maternal lineage that has not been detected in the South Island (n = 97). In addition, these animals have unique microsatellite alleles at three of the ten loci surveyed. A further four loci have alleles that are either fixed or at high frequency, yet are rare in South Island populations. Such differences over such a small geographic scale have not been observed in any other genetic studies of marine mammals. For example, two populations of Commerson's Dolphin Cephalorhynchus commersoni show less genetic difference, yet are separated by 8,500 km. The North Island subpopulation is therefore considered a subspecies (Baker et al. 2002).
Countries:	Native: New Zealand (North Is.)
FAO Marine Fishing Areas:	Native: Pacific-southwest

Population

Population:

On the basis of surveys conducted in 1984-1985 Dawson and Slooten (1988) estimated that the total population of Hector's dolphins was 3-4,000 individuals. The Maui's Dolphin population was estimated as 146 individuals (95% confidence interval 55-269) in 1985 (Dawson and Slooten 1988). The results of recent surveys suggest the population has declined to fewer than 100 individuals (Russell 1999) and that the range has been reduced.

An age structured model (Slooten et al. 2000) indicates that approximately 50% of Hector’s Dolphins are mature individuals. It is very plausible that fewer than 100 individuals remain in this population regardless of the survey used. Because only half are expected to be mature, it is plausible that fewer than 50 mature individuals remain.

Population Trend:

Habitat and Ecology

Habitat and Ecology:

Maui's Dolphin are found in inshore waters (Dawson and Slooten 1988). They are most common within about 5 nautical miles of shore.

System:

Marine

List of Habitats:

9.1	Marine Neritic - Pelagic
10.1	Marine Oceanic - Epipelagic (0-200m)

Threats

Threats:

The main threat to Maui's Dolphin is entanglement in gillnets (Dawson 1991, Slooten and Lad 1991, Dawson and Slooten 1993, Martien et al. 1999). Models that use current abundance together with entanglement rates and historical and current fishing effort indicate a high risk of population decline, and suggest that gillnet entanglement since 1970 has resulted in the Maui's Dolphin population declining to a third of its size before gillnet bycatch began (Martien et al. 1999). Additional threats include pollution, disease, vessel traffic (Stone and Yoshinaga 2000) and habitat modification.

List of Threats:

1	Habitat Loss/Degradation (human induced) (ongoing)
4.1.1.3	Accidental mortality - Bycatch - Fisheries-related - Entanglement (ongoing)
6.3	Pollution (affecting habitat and/or species) - Water pollution (ongoing)
8.5	Changes in native species dynamics - Pathogens/parasites (ongoing)
10.4	Human disturbance - Transport (ongoing)

Conservation Actions

Conservation Actions:

The New Zealand Marine Mammals Protection Act (MMPA) prohibits deliberate killing or injury of marine mammals. Bycatch in fishing gear is not illegal but by law can be regulated. Hector's Dolphin are listed as threatened under New Zealand legislation, bringing its classification in line with the previous IUCN listing of the species as Vulnerable (VU).

List of Conservation Actions:

1.2.1.2

Policy-based actions - Legislation - Development - National level (in place)

Bibliography

Bibliography:

Baker, A.N., Smith, N.H. and Pichler, F.B. 2002. Geographic variation in Hector's dolphin: recognition of new subspecies of Cephalorhynchus hectori. Journal of The Royal Society of New Zealand 32: 713-727.

Dawson, S.M. 1991. Incidental catch of Hector's dolphins in inshore gillnets. Marine Mammal Science 7(3): 283-295.

Dawson, S.M. and Slooten, E. 1993. Conservation of Hector's dolphins: The case and process which led to establishment of the Banks Peninsula Marine Mammal Sanctuary. Aquatic Conservation: Marine and Freshwater Ecosystems 3:207-221.

Dawson, S.M. and Slooten, E. 1998. Hector's Dolphin Cephalorhynchus hectori: Distribution and abundance. Reports of the International Whaling Commission, Special Issue 9:315-324.

Martien, K.K., Taylor, B.L., Slooten, E. and Dawson, S. 1999. A sensitivity analysis to guide research and management for Hector's dolphin. Biological Conservation 90:183-191.

Reeves, R.R., Smith, B.D., Crespo, E.A. and di Sciara, G.N. (compilers) 2003. Dolphins, Whales and Porpoises: 2002-2010 Conservation Action Plan for the World's Cetaceans. IUCN/SSC Cetacean Specialist Group. IUCN, Gland, Switzerland and Cambridge, UK.

Russel, K. 1999. The North Island Hector's dolphin. MSc thesis, University of Auckland, New Zealand.

Slooten, E. and Lad, F. 1991. Population biology and conservation of Hector's dolphin. Canadian Journal of Zoology 69:1701-1707.

Slooten, E., Fletcher, D. and Taylor, B.L. 2000. Accounting for uncertainty in risk assessment: Case study of Hector's dolphin mortality due to gillnet entanglement. Conservation Biology. 14:1264-1270.

Stone, G.S. and Yoshinaga, A. 2000. Hector's dolphin (Cephalorhynchus hectori) calf mortalities may indicate new risks from boat traffic and habituation. Pacific Conservation Biology 6(2): 162-171.

Citation:	Slooten, L. & Taylor, B.L. 2000. Cephalorhynchus hectori ssp. maui. In: IUCN 2007. 2007 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Downloaded on 28 August 2008.
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