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Set netting may cause extinction of NI dolphin

Forest and Bird Protection Society PO Box 631, Wellington

Media Release - Wellington - 15 February 2000

Hector's Dolphin Petition Supported

Conservationists fear that set netting may cause the extinction of the North Island population of Hector's dolphin.

The Forest and Bird Protection Society today called for a ban on set netting in Hectors dolphin areas and said it supported the petition of the New Zealand Whale and Dolphin Trust.

Society spokesperson, Barry Weeber, said Hector's dolphin was one of two endemic marine mammals found in New Zealand waters and was internationally recognised as a threatened species.

"Hector's dolphin is one of the rarest marine dolphins and is highly susceptible to being caught in set nets. Hundreds of these unique dolphins have been caught in set nets over the last 15 years."

Mr Weeber said the Society is calling for a prohibition on set netting in areas where the dolphins live.

"We are pleased to be able to join with the Whale and Dolphin Trust and Otago University students in campaigning for the future of one of the world's rarest dolphins."

Mr Weeber said there are three genetically distinct populations of the dolphin: on the North Island's West Coast and on the western and eastern coasts of the South Island.

"In each of these areas dolphins have been found washed ashore with marks consistent with being drowned in set nets."

"New Zealand must protect each population to meet its international commitments under the Biodiversity Convention. The West Coast North Island population is most at risk with less than 100 dolphins found in the latest survey."

Mr Weeber said urgent management action is required now rather than waiting for further research.

"Given the level of set netting off the West Coast of the North Island and the small size of the dolphin population there, it was critical that action be taken this year."

Mr Weeber said it should be a priority to establish a marine mammal sanctuary on the West Coast of the North Island between Hokianga Harbour and the Wanganui River out to 10 km off the coast.

"The removal of set nets from this area would be a major advance in the protection and rebuilding of the critically depleted West Coast North Island population."

Mr Weeber said Forest and Bird also supported a major expansion of the existing Bank's Peninsula Marine Mammal Sanctuary to cover the coast from Timaru to Motunau.

"Set nets bans were also needed in the South Island west coast waters where dolphins were being killed."

For further information contact Barry Weeber (04)385-7374.

February 1999 Background information on Hector's Dolphin

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 set nets since at least 1980. Red lists or red data books of threatened species have been prepared for almost 30 years by IUCN. 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 the Wanganui River. 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 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 set nets deaths (Martien et al, 1999).


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 sets nets and trawl nets but the vast majority of the reports are from set nets. Around Banks Peninsula sets 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 set nets, a legal requirement of the Marine Mammal Protection Act. It wasn't till a scientific observer programme was undertaken of set 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 set 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 set-netting is banned all year round and recreational fishing is prohibited between 1 November and the end of February.

This restrictions on set netting has almost eliminated set 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 set nets.

Other areas:

Dolphins have been reported drowned with marks attributed to set 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 set nets?

The fishing industry is continuing to propose an increase in the catch limit for elephant fish (a shark) which is caught by set nets for the quota management area that includes the East Coast of the South Island. The Minister of Fisheries previously rejected a proposal to increase the catch by 50% because of concern over dolphin deaths.

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 to confirm this during which up to 100 dolphins could drown.

This would require an 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 1-2 individuals a year being killed by set nets from both recreational and commercial fishers (Dawson and Slooten, 1993). For the smaller West Coast North Island population no set nets deaths can be accepted.

Urgent management Action Needed:

Given these uncertainties and the risk to the dolphin, in particular the West Coast North Island population, Forest and Bird see only one option that is banning set nets where Hector's dolphin live.

Urgent management action should be taken to reduce Hector's dolphin deaths from set nets by:

1. Establishing a marine mammal sanctuary on the West Coast of the North Island to protect the critically endangered and genetically isolated population found there. This should run from Wanganui to the Hokianga and extend 10 km offshore.

2. Expanding the Banks Peninsula Marine Mammal Sanctuary to include the area from Motunau to Timaru with a total ban on commercial and recreational gill netting in the extended sanctuary.

3. Further research by the Department of Conservation aimed at developing more marine mammal sanctuary's and a ban on set netting to protect the dolphin populations on West Coast of the South Island and in Southland.

4. Rejection by the Minister of Fisheries of proposals to increase the elephant fish catch limit.


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.

Barry Weeber Senior Researcher Royal Forest and Bird Protection Society PO Box 631 Wellington New Zealand Phone 64-4-385-7374 Fax 64-4-385-7373

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