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Hector’s Dolphins – Saved From Extinction

North Island Hector’s Dolphins – Saved From Extinction

Forest and Bird congratulates the Minister of Fisheries, Pete Hodgson and the Minister of Conservation, Sandra Lee, on their initiative to save the North Island Hector’s dolphins.

“There are only about 100 North Island Hector’s dolphins left and the Ministers’ decision is a major step forward in saving the dolphins,” said Eric Pyle, Forest and Bird’s Conservation Manager.

“The removal of gill nets from this area is a major advance in the protection and rebuilding of this critically-endangered dolphin population,” said Mr Pyle. A survey in 1999 for the Ministry of Fisheries confirmed that Hector’s dolphins are caught in gill nets on the West Coast of the North Island along with other dolphins and seals.” Mr Pyle said the prohibition of set nets will also protect penguins and shags which are also drowned in set nets.

Forest and Bird also supports an observer programme for trawlers. “It is important to have observers on trawlers in the area, because trawlers pose a threat to the dolphins too.”

Forest and Bird acknowledges the efforts the commercial set-netters made to develop solutions to this issue. “At the end of the day set netting in the dolphins’ range poses a substantial threat to the dolphins,” said Mr Pyle.

Forest and Bird is now recommending that part of the area from which set nets have been prohibited should be established as a marine mammal sanctuary.

Mr Pyle said the Society also welcomed the current consultation measures to protect Hector’s dolphin in the East Coast of the South Island and in Southland.

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Notes to Editor:

Hector’s dolphin is the world’s smallest and possibly the rarest marine dolphin with a population of 3-4,000. They occur only in New Zealand’s inshore waters and are rarely found more than 8 km from the coast.

Hector’s dolphin was gazetted late last year by the Minister of Conservation as a threatened species under section 2(3) of the Marine Mammals Protection Act 1978.

The dolphin is classified as a vulnerable threatened species in the most recent IUCN-World Conservation Union listings of globally threatened animal species (1996) . This listing is based on its small population size and the large number of dolphins drowned in gill nets since at least 1980. The Cetacean Specialist Group of the Species Survival Commission of IUCN, the world scientific experts on cetacean conservation, have assessed Hector’s dolphin as a threatened species of vulnerable status using the agreed threatened species criteria.

The dolphins mainly occur around the South Island but an additional population lives on the West Coast of the North Island between the Kaipara Heads and near New Plymouth. The main populations are found between Motunau and Timaru on the East Coast of the South Island, on the West Coast of the South Island, and in Foveaux Strait-Te Waewae Bay area in Southland.

Genetic work carried out by Auckland University indicates there are at least three relatively distinct populations of Hector’s dolphins (Pichler et al 1998) - East Coast South Island, West Coast South Island, and West Coast North Island. This means that each population must be managed separately when considering human impacts. The West Coast of the North Island population has been reduced to around 100 individuals between Taranaki Bight and the Manukau Harbour. Current research indicates that the west coast populations have been declining due to gill nets deaths (Martien et al, 1999). A survey by the Ministry of Fisheries of commercial gill netters confirmed they catch Hector’s dolphin, as well as other dolphins and seals. A workshop in May agreed that for the North Island population to recover less than one dolphin per five years would have to drown in gill nets.

Biology
About 95 percent of the population is found around the South Island. Dolphins live to around 20 years old with females calving at 7-9 years old and males reaching sexual maturity from 6-9 years old. Females appear to calve only once every two to four years. Hector’s are probably the world’s smallest dolphin with a mature length of 119-145 cm and weighing up to 58kg.

Fisheries impacts:
Hector’s dolphins have been recorded drowned in both gill nets and trawl nets but the vast majority of the reports are from gill nets. Around Banks Peninsula gill nets were estimated to drown over 230 dolphins between 1984 and 1987 (Dawson and Slooten, 1993).

Both commercial and recreational fishers have failed to report Hector’s dolphin deaths in gill nets, a legal requirement of the Marine Mammal Protection Act. It wasn’t till a scientific observer programme was undertaken of gill net and trawl vessels off the Canterbury coast that the true level of dolphin deaths was confirmed. As the previous Minister of Conservation, Nick Smith, said “What makes me particularly angry is that fishermen have for years failed to report fatalities and denied there was a problem”.

In the 1997-8 a Department of Conservation observer programme on commercial vessels recorded the deaths of six Hector’s dolphins. Observers covered only 89 of 351 fishing days. “I remain cynical that fishermen claim there were no deaths during the 262 days when observers were not present,” former Conservation Minister Nick Smith said. It is clear that neither commercial nor recreational gill netters are reporting deaths of Hector’s dolphin.

Past Management Action:
Banks Peninsula:
In response to dolphin deaths in the 1980s the Banks Peninsula Marine Mammal Sanctuary was established late in 1988. It covers an area of 1140km2 around Banks Peninsula from Rakaia River to Sumner Head. The Sanctuary extends 4 nautical miles offshore and commercial gill-netting is banned all year round and recreational fishing is prohibited between 1 November and the end of February.

This restriction on gill netting has almost eliminated gill net deaths in the sanctuary but dolphins are still being killed north and south of the Sanctuary. Forest and Bird considers the sanctuary should be extended to include the area from Motunau to Timaru where a significant number of dolphins have been drowned in gill nets.

Other areas:
Dolphins have been reported drowned with marks attributed to gill nets around Taranaki and on the West Coast of the North Island. No management action has been taken to protect Hector’s dolphin in these areas.

More gill nets?
The Minister of Fisheries has agreed to an increase in the rig and elephant fish catch on the East Coast of the South Island. Both species are caught by gill nets. The proposed limit of seven animals is arbitrary and was agreed without consultation with the Minister of Conservation as required by section 15 of the Fisheries Act 1996.

The fishing industry is arguing that the use of pingers (noise generating devices) on nets can reduce dolphin deaths. To work pingers must not fail (they are battery powered), the right frequency must be used, the dolphins must not habituate to them and many pingers must be used per net. It is unclear whether they will work and it could take 6 years of independent observation to confirm this during which up to 100 dolphins could drown if used on the East Coast of the South Island.

This would require a dedicated observer programme. A recent International Whaling Commission (IWC) Sub-committee meeting on cetaceans raised concern at “pingers being deployed without any apparent attempt to either test their efficacy nor to monitor their effects”. They noted that “harbour porpoises and short-beaked common dolphins are the only cetacean species for which properly designed studies..have been conducted to evaluate pinger effectiveness. Nevertheless, some bycatch has occurred in nets with active pingers during experiments and seatrials”.

The IWC Committee was also concerned that dolphins could become habituated to the pingers so that, while there may be an initial drop in deaths, the rate may increase over time as dolphins get used to the pingers. This seems to have occurred with harbour porpoises where the main trial has taken place.

Previous work has indicated that the dolphin population at Banks Peninsula can only withstand around 1 individuals a year being killed by gill nets from both recreational and commercial fishers (Dawson and Slooten, 1993). For the smaller West Coast North Island population no gill nets deaths can be accepted.


References:
Department of Conservation and Ministry of Fisheries (1994) Review of the Banks Peninsula Marine Mammal Sanctuary: A paper for public comment. June 1994. Canterbury Conservancy Misc Report Series No 3. 34p.
Department of Conservation (comp) (1992) Banks Peninsula Marine Mammal Sanctuary Technical Report, July 1992. Canterbury Conservancy Technical Report Series 4. 84p.
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 Vol 3: 207-221.
(1996) Down-under dolphins – the story of Hector’s dolphin. Canterbury University Press. 60p.
Dawson S M, Read A and Slooten E (1998) Pingers, Porpoises and Power: Uncertainties with using Pingers to reduce bycatch of small cetaceans. Biological Conservation 84: 141-146.
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.
Pichler F B, Dawson S M, Slooten E and Baker C S (1998) Geographic isolation of Hector’s dolphin populations described by Mitochondrial DNA sequences. Conservation Biology 12:676-682.
Slooten E and Lad F (1991) Population biology and conservation of Hector’s dolphin. Canadian Journal of Zoology 69: 1701-1707.


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