Doubtful Sound bottlenose dolphin: Threat management discussion paper
IntroductionSubmitted 4 September 2007: The New Zealand Conservation Authority considers that an immediate and precautionary approach needs to be taken to protect the bottlenose dolphin.
Date of submission: 4 September 2007
Submitted to: Department of Conservation
New Zealand has taken a world-leading position both nationally and internationally with respect to the conservation and protection of marine mammals. There has been a decline in the number of dolphins present in Doubtful Sound for more than a decade.
The New Zealand Conservation Authority considers that an immediate and precautionary approach needs to be taken to protect these animals.
- It is important that firm measures, reflecting the best information currently available, are put in place as soon as possible. While more efforts are required to fully identify the factors contributing to the population decline, it is important that actions to address the situation are not delayed.
- All stakeholders need to be involved in the protection and on-going conservation of this population.
- Restrictions on vessel movements within Doubtful Sound need to be implemented.
- The Marine Mammal Care Code should be formally adopted and enforced.
The establishment of marine mammal sanctuaries is justified to further protect this population.
Cetacean research both in New Zealand and internationally has shown that vessels have an impact on dolphin populations. It is the NZCA view that all vessels and their operators need to be part of the solution – regardless of whether the vessels are motorized or not, recreational or research, commercial or tourist, or for management. It is important that all vessels are subject to the same conditions and restrictions where they may come in contact with the dolphins – the dolphins are unable to distinguish between an encounter with a recreational boat or with a research boat.
In order for long-term sustainable use of Doubtful Sound consistent with the preservation of a viable dolphin population, all parties need to be engaged and their knowledge and experience built into the solutions that are developed.
Research in Doubtful Sound has identified areas where important resting and socializing activities occur. The establishment of marine mammal sanctuaries in at least some of these areas appears to be a logical step in reducing pressures on the dolphin population (e.g. in Crooked Arm, Bradshaw Sound).
General comments on the discussion document
The decline in the bottlenose dolphin population in Doubtful Sound from 69 to 56 individuals within a 12 year period (1994-2006) coupled with a high rate of still-births is serious, and it is appropriate that the Department of Conservation is seeking to both inform interested parties and seek engagement in identifying solutions and possible “management options which could slow or even possibly prevent this decline”.
Unfortunately this Discussion document raised a number of questions and did not provide sufficient information to assess the current context or the way in which the situation has altered in the period since 1994.
There is no information provided for comparative purposes on the birth rates and rates of still-births of other bottlenose dolphin populations; even within the wider Fiordland context. It is therefore not known whether the experience in Doubtful Sound is within the normal range for bottlenose dolphins.
Boating operations on Doubtful Sound
- There is no information provided in this Discussion Document on how boating on Doubtful Sound has changed since 1994. Although one presumes that use of the fiord by vessels has increased, no data are provided.
- Some information is provided about current boat operations but this focuses on tourist operations. Only a restricted amount of information is provided about recreational use and there is no mention of research vessels, Department of Conservation vessels servicing staff and operations within the Sound, commercial vessels (other than tourist vessels). Nor is there information on how use of the Doubtful Sound complex may have changed over time.
- The limited amount of data provided is not expressed in a manner than is easy to compare. It may be more helpful to have numbers of recorded encounters with dolphins or numbers of sightings as well as hours of boat time on Doubtful Sound (as one presumes that boat operators do not necessarily see all dolphins that come within within 300-400 m of their vessels, the distance within which there is apparently an effect on dolphins).
- The establishment of marine reserves and marine protected areas within the fiord is not referred to in this document. Has the establishment of these areas increased general tourist visitation – either private individuals or through diver charters, excursions? Has this had an impact on overall visitor and vessel numbers?
Effects of boating operations
Information is provided about definitions of interactions between dolphins and vessels, and of the impacts of the research vessels on dolphin behaviour.
- It is stated that over 70% of boat interactions observed during a 1999-2002 study violated the Marine Mammal Protection Regulations 1992. There is no information on whether the situation in 2007 has changed from that observed in 1999-2002.
- It is postulated that boat interactions have a significant energetic cost which may result in reduced reproductive success – while we accept that this is a serious risk, there are no data provided to evaluate the extent of the increase in boating pressures in Doubtful. If boat use of the fiord needs to be restricted, should it be returned to 1994 levels, 1999 levels…? What is the level that is deemed appropriate and acceptable?
- There is no information on how many hours of research boat and observational time were spent at each of the three levels of “observational intensity” and on other purposes. It is critical that any scientific permits for vessel use are reviewed. Although the document asserts that “decreasing the amount of research conducted will impact the ability to make informed decisions to protect the dolphins” it does not appear to be further information on dolphin behaviour that is required – but rather information on boat visits, vessel operator behaviour and the changing uses of the fiord – as well as on food web dynamics and environmental variability. It appears that a great deal of observational research has already been carried out on the very small dolphin population in this fiord.
- There may be other factors contributing to the decline in the dolphins - by putting limits on boat interactions, New Zealand will be having regard to research which has traction internationally including with the IWC. If there is no improvement in the population subsequently we will know that that boat interactions generally were not the critical factor and meanwhile further research can take place into other aspects or look more closely at different types of boat interaction effects.
The paper states “Boat interactions are identified as a key cause linked to the decline of the bottlenose dolphin population in the Doubtful Sound complex”. This section then goes on to state that alongside options for increasing the protection of dolphins which are discussed later in the document “an understanding of other threats facing this population and a clear strategy to address these threats must be established”.
- Boat strikes – is there any evidence for these in Doubtful Sound?
- Food sources – there has been detailed research on food webs in Doubtful Sound by University of Otago workers (Wing and co-workers) – is any of this research of relevance to this question – and is there any evidence that food sources/supplies have altered since 1994?
- Freshwater Discharge – given that only 1/3 of the freshwater input to Doubtful is from natural runoff, rainfall and discharges, is there any evidence that would suggest that the increased outfalls which have been enabled by the new tunnel from Manapouri will be deleterious? if the precautionary principle is employed in Doubtful Sound in order to secure this dolphin population should increases in outflows be restricted? what data would enable such decisions to be made? is research on food webs and food supply of dolphins currently underway?
- Disease – is there information about Brucella in other bottlenose populations in New Zealand – or elsewhere? Is there information on the rates and changes in rates of still births in other bottlenose populations?
- Gene Pool –research has been undertaken and the results supplied to Department of Conservation on the genetics of bottlenose populations in New Zealand, including Fiordland populations. If our understanding is correct, it would have been helpful to have had such information available to the public and interested parties in this topic.
- Climate variability – what data are available on seawater temperature, salinity, productivity in the water of Doubtful Sound and adjacent oceanic waters in the period 1994-2007 – have any changes been observed? have there been any noticeable impacts of El Nino/La Nina events on conditions experienced in Doubtful Sound or adjacent oceanic waters? There have been a number of oceanographic and physical/chemical studies in this fiord and no data summarizing this knowledge is cited or provided.
The New Zealand Conservation Authority urges that actions are taken promptly to increase the effective protection of the population of dolphins in Doubtful Sound with a view to halting its decline and enabling its recovery to healthy and sustainable levels. The situation justifies a precautionary approach being taken which will demonstrate to all interested parties that the situation is recognised as serious and there is a will to take resolute action. When and if additional data comes to hand that suggests that other measures are required or would be more appropriate then those adopted now can be reviewed.
The Fiordland (Te Moana o Atawhenua) Marine Management Act 2005 and the establishment of the Guardians of Fiordland established a new model for the management of resources in New Zealand which put emphasis on preservation, protection and sustainability for long-term benefit ahead of immediate benefits. The New Zealand Conservation Authority advocates the application of the model to the Doubtful Sound dolphins and other marine mammals to no lesser degree than it has been to the fishery.
- Discussion document: Doubtful Sound bottlenose dolphin (PDF, 1005K)
- Bottlenose dolphins
- Effects of tourism on behavioural ecology of bottlenose dolphins of northeastern New Zealand (PDF, 326K)