Cephalorhynchus hectori 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Cetartiodactyla Delphinidae

Scientific Name: Cephalorhynchus hectori (van Beneden, 1881)
Infra-specific Taxa Assessed:
Common Name(s):
English Hector's Dolphin, New Zealand Dolphin, New Zealand White-front Dolphin, White-headed Dolphin
French Dauphin d'Hector
Spanish Delfín de Héctor, Tunina de Héctor
Taxonomic Notes: The North Island subpopulation of Hector’s Dolphin was recognized recently as a subspecies, Cephalorhynchus hectori maui (Baker et al. 2002), and it has been assessed separately. This subspecies is sometimes referred to as Maui’s Dolphin (not Maui’s Hector’s Dolphin).

Assessment Information [top]

Red List Category & Criteria: Endangered A4d ver 3.1
Year Published: 2013
Date Assessed: 2008-07-01
Assessor(s): Reeves, R.R., Dawson, S.M., Jefferson, T.A., Karczmarski, L., Laidre, K., O’Corry-Crowe, G., Rojas-Bracho, L., Secchi, E.R., Slooten, E., Smith, B.D., Wang, J.Y. & Zhou, K.
Reviewer(s): Brownell Jr., R.L. & Cooke, J.
This species is considered to be Endangered A4d due to an ongoing and projected decline of greater than 50% over 3 generations (approx. 39 years, Slooten et al. 2000) considering both the past and the future. It is also important to consider that although its extent of occurrence and area of occupancy likely exceed the thresholds for criteria B1, B2 and D2, Hector’s Dolphin has the most limited range of any marine cetacean other than the Vaquita (Phocoena sinus). In a population viability analysis, the estimated rate of decline was 74% over 3 generations where the time period under consideration was from 1970-2009 (Slooten 2007). The main cause of population decline is ongoing bycatch in fisheries.
Previously published Red List assessments:

Geographic Range [top]

Range Description:Hector’s Dolphin is endemic to New Zealand, and it has one of the most restricted distributions of any cetacean (Dawson and Slooten 1988; Dawson 2002). They are most common off the South Island and the west coast of the North Island. There are at least three genetically separate populations in the South Island, and a single small North Island population (C. h. maui - Baker et al. 2002).

The map shows where the species may occur based on oceanography. The species has not been recorded for all the states within the hypothetical range as shown on the map. States for which confirmed records of the species exist are included in the list of native range states.
Countries occurrence:
New Zealand (North Is., South Is.)
FAO Marine Fishing Areas:
Pacific – southwest
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Studies of mitochondrial and nuclear DNA show that North Island Hector's dolphins are genetically distinct from any of the South Island subpopulations, with no overlap of maternal lineages between them (Pichler et al. 1998). Such differences over such a small geographic scale have not been observed in any other genetic studies of marine mammals (Dawson et al. 2001).

Recent surveys indicate that the South Island Hector’s dolphin populations collectively number about 7,270 individuals (CV = 15.8%) (Dawson et al. 2004; Gormley et al. 2005). The North Island subspecies is estimated to number about 111 (CV = 44%), and that population’s abundance and range appear to have been declining rapidly over the past 30 years (Slooten et al. 2006b; Dawson et al. 2001).
Current Population Trend:Decreasing
Additional data:
Number of mature individuals:7381-7381
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:The habits and biology of Hector's dolphin have been well studied in the last couple of decades, and this is undoubtedly the best-known species of the genus (Dawson 2002). It is found in shallow coastal waters, almost always within about 15 km of shore and <100 m deep, strongly concentrated in shallow, turbid waters close to shore in summer months and dispersing more widely in winter (Slooten et al. 2006a). Photo-identification studies have demonstrated that at least some individuals are resident in small areas (about 30 km of coastline) year-round (Slooten et al. 1993). No two sightings of an individual have been more than 106 km apart (Bräger et al. 2002).

Hector's dolphins feed on several species of small fish and squid (Dawson 2002). The diet is more varied on the east coast of the South Island (8 species make up 80% of the diet) than on the west coast (only 4 species make up 80%).

Threats [top]

Major Threat(s): Hector’s dolphin faces serious pressures from human activities given its limited coastal distribution. The main threat to the species in general is entanglement in gillnets (Dawson 1991; Slooten and Lad 1991; Dawson and Slooten 1993; Martien et al. 1999; Secchi 2006; Slooten 2007; DOC and Mfish 2007), with trawl fisheries also causing some mortality. Amateur gillnetting (as opposed to commercial gillnetting) is a significant part of the problem (Dawson and Slooten 2005). Sixty percent of all dead Hector’s dolphins for which cause of death could be determined, had died as a result of gillnet entanglement (DOC and Mfish 2007). Risk analyses for Hector’s and Maui’s dolphins indicate that recent levels of mortality are unsustainable (Slooten and Lad 1991; Martien et al. 1999; Slooten et al. 2000; Burkhart and Slooten 2003; Slooten 2007; DOC and Mfish 2007). This conclusion is robust to the uncertainty in abundance, mortality, and vital rates (Slooten et al. 2000; Slooten 2007). The most recent population viability analysis indicates continued population declines (Slooten 2007). Additional threats include pollution, disease, vessel traffic, and habitat modification (Stone and Yoshinaga 2000).

Conservation Actions [top]

Conservation Actions: The species is listed in CITES Appendix II.

The entire range is within New Zealand waters, and therefore national conservation measures are discussed here. The New Zealand Government has created two protected areas to promote the conservation of C. hectori, and it is thought that these areas have contributed to reduced mortality in recent years. The Banks Peninsula Marine Mammal Sanctuary was established in 1988 under the Marine Mammals Protection Act to protect Hector’s dolphins. The 1,170 km² sanctuary extends 70 nautical miles alongshore around the Banks Peninsula to the Rakaia River and out to 4 nautical miles offshore (Dawson and Slooten 2005). Its effectiveness has been compromised by the interests of sports and commercial fishermen and by the fact that the dolphins’ offshore distribution extends beyond the protected area (Dawson and Slooten 1993). At Banks Peninsula the dolphins are found further offshore than elsewhere, probably because the bathymetry there slopes more gradually. Up to 65% of the dolphins in the area occur outside the sanctuary boundaries in winter months (Slooten et al. 2006a).

The protected area established for Maui’s dolphins stretches for 210 nautical miles along the west coast of the North Island out to 4 nautical miles offshore. Although this area was closed to gillnetting under the Fisheries Act in 2003, gillnetting has continued inside the harbors, and trawling is restricted only within the first nautical mile offshore (Slooten et al. 2006b).

Discussions between the Ministry of Fisheries and Department of Conservation are currently (early 2008) underway to develop a more comprehensive management plan. A continuing high level of bycatch mortality indicates that stronger protection from entanglement in commercial and recreational fisheries is needed. Protected areas, reduced gillnet fishing effort and changes in fishing methods have been recommended as necessary to ensure the species’ long-term persistence (e.g. Martien et al. 1999, Burkhart and Slooten 2003, Slooten 2007; DOC and Mfish 2007). Meetings of stakeholders have concluded that fishery mortality must be reduced to zero to allow the North Island subspecies to recover (Dawson et al. 2001; Slooten et al. 2006a). Several other small subpopulations (100 individuals or fewer) are at a similar risk from entanglement (Burkhart and Slooten 2003; Slooten 2005). Recent surveys (Dawson et al. 2004, Slooten 2005, Slooten et al. 2006a,b) indicate that restricting gillnet fisheries to waters >100 m deep would have a major benefit in terms of reducing bycatch. In waters <100 m deep it would also be advisable to institute observer programs on any trawl fisheries that operate in Hector’s dolphin habitat.

Citation: Reeves, R.R., Dawson, S.M., Jefferson, T.A., Karczmarski, L., Laidre, K., O’Corry-Crowe, G., Rojas-Bracho, L., Secchi, E.R., Slooten, E., Smith, B.D., Wang, J.Y. & Zhou, K. 2013. Cephalorhynchus hectori. The IUCN Red List of Threatened Species 2013: e.T4162A44199757. . Downloaded on 20 September 2018.
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