The almost instant popularity of whalewatching at Kaikoura persuaded the Department of Conservation to undertake a number of research initiatives, to establish a scientific basis for the management of whalewatching.
One of the Department's first priorities was to commission a comprehensive review of the international literature on whale responses to anthropogenic sounds. This review (Reeves 1992) confirmed that most overseas studies have focused on baleen whales and some small toothed whales and that very little information is available on sperm whales.
The Royal New Zealand Navy was also contracted to provide technical advice to the Department of Conservation on underwater noise produced by tourist operations (Defence Scientific Establishment 1992, Trial Analysis Unit 1992 a,b).
Background ambient noise averages around 60 decibels in New Zealand waters and well over 70 decibels in north-eastern Pacific waters. Noise generated from tourist boats and aircraft is not greatly dissimilar from the levels that cetaceans normally have to cope with (Figure 3) (Defence Scientific Establishment 1992).
One of the most significant conclusions reached by the Navy's acoustic specialists relates to the transmission of noise from air to water. Noise arrives at the sea's surface radiating out from its source (Figure 4). Inside an angle of approximately 131 sound penetrates the water with some reflection from the surface. Refraction at the air-water interface disperses the sound as shown in Figure 4. Beyond 131, however, sound is mostly reflected from the sea's surface and sound transmission into water is considerably reduced. Although sea conditions will influence sound transmission into water, the model described above shows that aircraft noise should not generally be a problem for whales and dolphins provided aircraft keep clear of an envelope shaped like an inverted 13' cone above the animals (Figure 5).
In other words, aircraft should not fly directly over marine mammals at low altitudes, but rather circle them at a distance. This model, with built-in safety margins, has been used to determine the minimum aircraft approach distances in the regulations. Figure 5 also demonstrates that marine mammals will probably not be able to hear an aircraft approaching until it is suddenly overhead. Sudden noises can startle cetaceans, reinforcing the need for aircraft not to fly directly over pods of dolphins or whales.
Sudden noise is similarly a concern with respect to the operation of vessels in the vicinity of cetaceans. Noise can travel considerable distances underwater and whales and dolphins will be aware of an approaching boat from a long distance away. Sudden noise changes through boats abruptly altering course or speed are known to startle sperm whales at Kaikoura. Even placing motors in and out of gear can elicit a negative reaction. Accordingly, the regulations prohibit vessels from making sudden or repeated changes in speed or direction.
Besides the literature review and assessment of sound transmission through sea water, two specific field projects have been commissioned by the Department of Conservation to assess the impact of marine mammal watching on sperm whales at Kaikoura.
In 1990, a post graduate student from Canterbury University spent several months monitoring sperm whale surface behaviour in the presence and absence of whale watch boats (MacGibbon 1991). A further study was undertaken in 1992 by a team of researchers from Oxford University led by Dr Jonathan Gordon (Gordon et al, 1992). The latter study investigated underwater acoustic behaviour as well as surface behaviour. Gordon (1992) confirmed MacGibbon's earlier findings with respect to the surface response of sperm whales to whale watch boats. Responses are highly variable between individual whales. On average, however, whales appear to spend shorter periods on the surface and have shorter ventilation intervals when boats are around. Ventilation rates also seem to be more variable when boats are present.
Gordon (1992) also found that the acoustic behaviour of sperm whales immediately after diving was significantly different when boats were present, although, overall, sperm whale vocalisations appeared to be unaffected by the presence or absence of boats.
Some very obvious signs of whales being disturbed by whale watch boats were observed, notably whales diving without 'fluking-up' (Figure 6) (MacGibbon 1991; Gordon et al 1992). Such shallow dives are thought to be evasive manoeuvres and generally occurred when boats failed to follow the regulations.
Since 1993, Drs Steve Dawson and Elisabeth Slooten of Otago University, in association with a number of their students, have been conducting a long-term study of the Kaikoura sperm whale population. The study is focused on individual identification, growth rates and the development of acoustic survey techniques, but it has also provided information on the seasonal distribution and behaviour of sperm whales that is of relevance to management of whalewatching operations.
The sperm whale research to date has only been able to answer some of the questions relating to the impact of whale watching vessels at Kaikoura. It has demonstrated that whale watching causes some changes in the surface behaviour of sperm whales. Provided the regulations are adhered to, the impacts seem to be relatively undramatic (Gordon 1992), suggesting the current regulations are providing sperm whales with a reasonable degree of protection from whale watching vessels.
Nevertheless, the Department continues to adopt a very precautionary approach to any increased whale watching effort at Kaikoura. No further permits have been granted since 1989, despite numerous applications, nor have the existing operators been allowed to increase their number of trips. There has, however, been a trend for larger and quieter vessels to be employed in whale watching activities, thus delivering more passengers but having less potential impact on the behaviour of whales.
Until recently, research on the impacts of marine mammal watching has focused on sperm whales at Kaikoura. However, the rapid growth of the marine mammal tourism industry in New Zealand has led to the recent development of field projects to assess the impact of tourist boats and swimmers on dolphin behaviour. A workshop convened in Kaikoura in February 1992 concluded that dusky dolphin behaviour and social structure makes them vulnerable to disturbance on the surface. A research programme has since been established at Kaikoura (Barr, Slooten and Wursig, 1994), which involves observing the dolphins from a vantage point on a high cliff and plotting their movements in the presence and absence of tourist vessels on a theodolite interfaced with a laptop computer. The study forms the basis of an M.Sc. thesis (Barr in prep), the results of which should be available later this year.
Swimming with bottlenose and common dolphins is now well established in the Bay of Islands, one of the country's most popular tourist spots. A two-year research programme (Constantine and Baker 1994) is due for completion in June 1995. A photo-identification catalogue has been developed during the programme and the research so far (Constantine in prep) has shown that the number of bottlenose dolphins which frequent the Bay of Islands is far larger than had originally been believed, and that most of them are only resident within the Bay for short periods of time. This work is undertaken under contract to the Department of Conservation, and also forms the basis of an M.Sc. thesis. The research has also identified specific dolphin responses to approaches by boats, which essentially reinforce the approach method required by the Marine Mammals Protection Regulations (Annex 1).