Dolphins In Danger

Forest and Bird, Issue 296, 1 May 2000, Page 36

Dolphins In Danger

TISH GLASSON

reports on the threatened populations of Hector’s dolphin.

small grey flicker ran through the of the surf, just beyond the breakers. Instantly a school trip lunch stop, at Waikawa Harbour in eastern Southland, comes alive with excited youngsters who have just seen their first wild Hector’s dolphins. Unlike most places in New Zealand, dol-phin-watching in Porpoise Bay at the head of the harbour is easily accessible. Just walk along the beach and keep your eyes open. You can even swim with them from the beach, or rather let them swim with you. Southland people and ‘surfies’ who use the bay have known about the dolphins for many years. Now free dolphin-watching is on the backpackers’ grapevine and in the popular guidebooks. Concerns have been raised that increased visitor numbers in summer might disturb the small pod of 50 or so animals. Charter-boat operator Ivan MacIntosh says the dolphins swim with people in the surf because that is where the animals’ food is. The dolphins don’t like the swimmers, he says. One business offered wet suits and kayaks for hire to passengers from shuttle bus services, and did not have a marine mammalwatching permit. This put pressure on the dolphins because people were in the water with them most of the day, Ivan MacIntosh says. ‘Continual contact, that is the problem... that’s what the Hector’s get’ He has heard people standing on the beach comment that

the dolphins don’t really like people much. ‘We tell the ones who get upset to write to DoC... there’s got to be planning at Porpoise Bay, for sure. A local resident and voluntary guardian of the dolphins is Nancy Gee who says the district is getting a lot more tourists, mostly on day trips. Most visitors are in their 20s and 30s and many go into the water to swim with the dolphins in the bay. ‘Swimmers need to be aware there are protocols for meeting dolphins in their own environment. Splashing is a sign of aggression to dolphins. If swimmers want the animals to come close, it is better to stand still. Curiosity will gradually get the better of them, she says. ‘Generally people are pretty good. I say something to them and they soon find out it is not the way to behave, Nancy Gee says.

In Australia, at Monkey Mia north of Perth and at Tangaloom, Queensland, studies of these kinds of interactions showed a need for regulations. Strict controls have been put on visitor access and behaviour in places where people can approach dolphins easily from the shore. No one in Southland wants so much visitor pressure on the Porpoise Bay pod that the dolphins disappear. ll dolphins in New Zealand are proby the Marine Animals Act, which is administered by the Department of Conservation. DoC has issued two marine-mammal watching permits in the Waikawa area, one shore-based and the other for Ivan MacIntosh’s charterboat operation. There are presently no plans to introduce the Australian type of controls

for people swimming with dolphins from the beach. The Murihiku area manager for DoC, Dave Taylor, says the approach the department is taking is one of ‘education’. However, he acknowledges there are some issues which still needed to be resolved. ‘We're certainly looking at putting quite a lot of resources into that pod and we're mindful that some of the commercial interests are pushing the barriers; he says. DoC has had a paid warden at Porpoise Bay during this summer. Hector’s is the rarest type of dolphin and occurs only around the coast of New Zealand. A study programme by Dr Steve Dawson of the marine studies department at Otago University was investigating the species. Dr Dawson and his students were monitoring Hector’s dolphin numbers in Canterbury, the West Coast, Otago and Southland. (Auckland University was studying the small population on the west coast of the North Island.) An MSc student, Lars Bejder of Denmark, studied the Porpoise Bay pod in the summers of 1995-96 and 1996-97. Population counts were done by aerial surveys and from a specially adapted boat belonging to Dr Dawson. These counts have shown just how small the total population of Hector’s dolphin is. ‘We believe there are about 400 Hector’s between Timaru and Long Point (Fiordland), Dr Dawson says. "The population in Otago and Southland is tiny’ One major problem is the very slow breeding rate of Hector’s dolphins. They mate in late spring and calve, a year later, from then until about February. It is difficult to know exactly what the gestation period is, but scientists estimate it to be between 10 and 12 months. Only one calf is born at a time and at best Hector’s only give birth once every two years. The more usual rate is once every three years and population growth is estimated to be two percent annually. If a population of 100 animals had two deaths from natural causes during a year, a two percent reproduction rate is barely sufficient to keep the population stable. Hence the pod of 50 individuals in Porpoise Bay is particularly vulnerable and in the summer of 1998-99 only one calf was seen in the bay. This summer (1999-2000), two new calves have been seen, and last year’s baby has returned as a yearling. Recently, DNA studies have been used to establish the relationships between the various populations. Tissue samples were taken from dead dolphins caught in gill nets or washed up on beaches. The DNA of museum specimens has also been sampled.

Fortunately Hector’s dolphins are inquisitive enough to allow the approach of a boat they know. This allows researchers to collect a small tissue sample from a live dolphin, by gently scratching its back with a plastic potscrub attached to a pole. This gives enough skin cells to do a DNA test, similar to the sort used by forensic experts investigating crimes. The dolphins don’t appear to be upset by this procedure, Dr Dawson says. These DNA studies show the southern population of Hector’s dolphin is quite separate from those off Canterbury. In fact they seem more closely related to those on the West Coast. No Hector’s dolphin have been recorded on the Tasman Sea coast of Fiordland, so mixing of the two groups must be extremely rare, he says. DoC has been very responsible in taking a cautious approach in its management policies for the Porpoise Bay pod, according to Dr Dawson. Hopefully, kids on school trips through the Catlins area will be able to continue to experience the thrill of meeting the world’s smallest, rarest marine mammal in its own home.

Hector’s dolphin now a ‘threatened species’ n an early executive action, the new Minister of Conservation, Sandra Lee, has declared Hector’s dolphin a ‘threatened species. Under the Marine Mammals Act, the Minister must now improve protection for Hector’s dolphin, and see its popul;ation recover to ‘non-threatened’ within 20 years. Forest and Bird has responded by calling for a ban on set netting in areas frequented by Hector’s dolphin. ‘Hector’s dolphin is one of the rarest marine dolphins and is highly susceptible to being caught in set nets, according to Barry Weeber, a conservation officer with Forest and Bird. 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, he says. ‘New Zealand must protect each population to meet its international commitments under the Biodiversity Convention. The North Island west coast population is most at risk with less than 100 dolphins found in the latest survey. Conservationists fear that set netting could cause the extinction of this North Island population of Hector’s dolphin. ‘Urgent management action is required now rather than waiting for further research; says Barry Weeber. ‘Given the level of set netting off the west coast of the North Island and the small size of the dolphin population there, it is critical that action be taken this year. ‘It should be a priority to establish a marine mammal sanctuary out to 10 kilometres off the coast between the Hokianga Harbour and the Wanganui River. ‘The removal of set nets from this area would be a major advance in the protection and rebuilding of this critically depleted population. Forest and Bird also supports a major expansion of the existing Banks Peninsula Marine Mammal Sanctuary to cover the coast from Timaru to Motunau Island in North Canterbury. Set nets bans are also needed in the South Island west coast waters.