Research Technique May Help Save Maui's Dolphins
New Research Technique May Help Save Maui's Dolphins
The Department of Conservation is to trial satellite-tracking, a technique never before used on New Zealand dolphins, to help save the critically endangered Maui's dolphin from extinction.
Satellite-linked transmitters will be trialled on three South Island Hector's dolphins off Banks Peninsula to assess the technique's suitability for the closely-related Maui's dolphin, which lives off the North Island west coast.
Department of Conservation Auckland conservator Rob McCallum said this research method had the potential to reveal where the dolphins range and how far they travel offshore - information urgently needed to protect Maui's dolphins from fishing related threats.
"Our efforts to save New Zealand's rarest dolphin are being hampered by what we don't know about them. We need to find out if Maui's dolphins move outside the current set netting closed area. If so, we need solid evidence to show this and to determine how much of their time they spend in different areas."
"Satellite tracking shows great promise in helping to answer this question. It can give real-time information about where dolphins go, day and night, in all weather conditions and in a relatively short time frame."
Mr McCallum said other research methods currently in use such as aerial survey, acoustic devices and genetic studies, contributed to the picture of dolphin distribution but did not give all the information needed.
"Surveys are good for studying dolphins where you expect to find them, which runs the risk of giving a selective and incorrect picture of their total movements."
Satellite tracking has been used successfully overseas on other small dolphins and porpoises where it has sometimes revealed surprising results. Harbour porpoises in the Bay of Fundy, Canada, once thought to rarely leave their home coves, were shown to travel extensively out into the Atlantic Ocean, for example.
"Overseas researchers are questioning why New Zealand isn't using this technique to find out what is really going on with Maui's dolphin," said Mr McCallum.
Recently Maui's dolphins have been seen off New Plymouth, up to 100 kilometres south of the closed set netting area, but an aerial survey failed to spot the dolphins.
"With less than 150 Maui's dolphins left, we need to consider all means available to find out what we need to know to save this dolphin. We can't afford to wait," he said.
The custom-made satellite tags for the trial are one of the smallest and most streamlined marine mammal transmitters ever built. The tags are the length of two match boxes laid end-to-end and weigh about 50 grams (the weight of three 50 cent pieces).
Mr McCallum said the technique was not without risks, which is why it was being trialled first on the more numerous Hector's dolphins. The three month trial will start shortly.
A team of international and New Zealand experts including marine mammal scientists and a specialist veterinarian will conduct the trial.
The trial has been approved by Massey University's animal ethics committee and will be subject to strict conditions under a marine mammal research permit, which includes a comprehensive risk assessment.
The department has consulted with interested groups and has the full backing of Ngai Tahu to carry out the trial on the Banks Peninsula dolphins.
* Maui's dolphin is found only along part of the west coast of the North Island and is listed by the IUCN (The World Conservation Union) as "critically endangered".
* The dolphin used to be known as North Island Hector's dolphin but research has shown the North and South Island dolphins are separate sub-species.
* Fisheries regulations ban set netting within four nautical miles of the North Island west coast from Maunganui Bluff (north of Dargaville) to Pariokariwa Point (north of New Plymouth). Set nets are also prohibited in the Manukau Harbour entrance.
Questions and Answers on Satellite Tagging Trial
1. Satellite tagging is unnecessary - can't other methods such as aerial and boat surveying, acoustic devices etc give the information needed about dolphin distribution?
All methods have strengths and can illuminate part of the puzzle we are seeking answers to but they all have specific weaknesses.
Aerial survey is likely to remain the backbone of our research efforts but satellite tagging is the only method that can give continuous real-time data about the dolphin's movement - day and night and seasonal - within a short timeframe.
Aerial surveys and photo identification are limited to daylight hours and calm conditions and the dolphins can only be identified when they are close to the surface. Getting enough sightings can be difficult with such a small population (<150 dolphins).
We've conducted one trial using PODs (acoustic devices) which did not yield sufficiently positive results. We intend to conduct another trial with PODs because it shows potential for use in harbours where waters are calmer and the dolphins are more likely pass near the devices. But its value in the open sea is likely to remain questionable.
With less than 150 Maui's dolphins left, we need to try all means available to find out what we need to know to save this dolphin (this includes aerial survey, genetic sampling, observer programmes etc). We can't afford to wait.
2. Satellite tagging is invasive and poses unnecessary risks to the dolphins.
The proposed satellite tagging technique trial has been thoroughly risk assessed. Any risks to the dolphins of capture and tag attachment will be minimised through careful risk management and strict contract service standards for the expert team that will carry out the trial.
A highly experienced international team will carry out the trial. The team includes marine mammal scientists with extensive experience in capture and tagging and satellite telemetry, and a world leading specialist veterinarian.
The vet will monitor the animals' heart rate and stress levels. If a dolphin gets too stressed it will immediately be returned to the water.
Satellite tagging has been used successfully on small dolphins and porpoises overseas. The trial on Hector's dolphins will test its effectiveness on this species and assess potential risks.
The trial has been approved by an independent animal ethics committee (Massey University) and must meet research permit conditions under the Marine Mammals Act.
3. The accuracy of the ARGOS satellite's position is not reliable giving poor accuracy of dolphin positions.
Problems experienced with accuracy of satellite tagging previously are not relevant to this trial. The tags proposed to be used on Hector's dolphins (the SPOT-3 with Cricket 0.5 watt transmitter) are state-of-the-art and more accurate. This tag at NZ latitudes can give positions estimated at plus or minus 350 metres. The trial will test the position accuracy - this is one of its purposes.
4. There is evidence of dolphin dorsal fin damage from loss of tags in a study in North America between 1998 and 2000 - this could happen to Hector's dolphin?
The satellite tags used in the North American study used technology and fastening methods that are now out dated.
The tags proposed for the trial on Hector's dolphin are state-of-the-art and are attached with nylon coated pins to protect the dorsal tissue. They are designed to corrode and release from the animal (after 130 days). The tags should not damage or disfigure the dorsal fin.
5. How will you know the dolphins are all right after the transmitters stop transmitting?
The dolphins will be monitored as long as the transmitters continue to transmit but once they stop the dolphins may be difficult to find. The tags are designed to drop off after three months.
Banks Peninsula Hector's dolphins are observed and individually identified on a regular basis so the chance of subsequent sightings of the tagged dolphins is higher than for Hector's populations on the west coast of the South Island.
The only proven method of marking dolphins is freeze branding, which the department will not do.
6. Why three dolphins?
The trial needs to include enough individuals to obtain a valid result and three is thought to be the minimum number to yield this. The trial is a study of the technique and the technology and not designed to yield information on the Banks Peninsula Hector's dolphin population.
7. Is it true you will have to tag one-third of the entire Maui's population to get statistically significant results? If not, how many?
We don't know how many Maui's dolphins would need to be tagged. Some scientists suggest it could be as low as ten but we won't know until we can evaluate the research technique on Hector's dolphins. This is the reason we are conducting a trial.
8. Why doesn't DOC have a recovery plan for Maui's dolphin?
DOC doesn't yet have enough basic information about the
Maui's population and its distribution to provide the basis
for a recovery plan. We have an internationally peer
reviewed research strategy which poses the key research
questions and outlines the methods that could yield this