Responses of South Island Hector's dolphins (Cephalorhynchus hectori hectori) to vessel activity (including tourism operations) in Akaroa Harbour, Banks Peninsula, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Marine Biology at Massey University, Auckland, New Zealand
For over 25 years, tour operators have been undertaking view and swim-with-dolphin
trips in Akaroa Harbour off Banks Peninsula, east coast South Island, New Zealand.
Following the international exponential growth in the commercial dolphin-based
tourism industry, Akaroa Harbour is now a key eco-tourism destination in New
Zealand with 32 daily permitted trips targeting Hector’s dolphin (Cephalorhynchus
hectori hectori). Such a high number of trips is of particular concern given that this
species is not only endemic but also endangered. Our current understanding of the
effects of tourism activities on Hector’s dolphins in Akaroa Harbour is far from
satisfactory. To ensure the sustainability of the economically-important and rapidlygrowing
dolphin-based tourism industry, there is an urgent need for sound scientific
evidence on which to base management decisions.
One of the challenging issues with the assessment of tourism impacts is the lack of
baseline data. Prior to beginning the evaluation of the effects of disturbance on this
population, data relating to the occurrence and demographics of Hector’s dolphins, as
well as vessel traffic in Akaroa Harbour, were collected from land-based platforms
during three consecutive austral summers (November and March), commencing in
2005. Examination of Sighting Per Unit Effort (here number of dolphin sightings per
hour) and the dolphin fine-scale spatial distribution confirmed an inshore-offshore
migration and, in the case of the latter, higher density patterns between the Kaik hills
and the harbour entrance. However, no specific area was associated with a particular
behaviour or nursery groups. The majority of groups consisted of adults only (91.2%,
n = 2,000) and comprised mainly 2-5 individuals (83.2%). Group size varied with
behaviour, being larger when socialising. Activity budgets within two outer bays were
very comparable to Akaroa Harbour, except for socialising.
In the harbour, Hector’s dolphins only spent a small proportion (14%) of their day
(0600-1800 hr) in the absence of vessels. Vessel traffic in the harbour consisted
mainly of recreational vessels (72.9%) although commercial vessels represented
70.4% of observed encounters and interacted twice as long with the dolphins. No
displacement was evident and as a result, Hector’s dolphins might compensate for
high vessel traffic levels by adjusting their behavioural budget.
To determine the effects of tourism activities on Hector’s dolphins’ behavioural
budget, focal-group follows using a scan sample methodology were conducted from
land-based stations and analysed using Markov chain models (n = 330 sequences).
Vessel presence affected the activity budget of Hector’s dolphins by changing
transition probabilities, bout durations and the time taken to return to a behavioural
state once disrupted. Both diving (inferred foraging) and travelling were significantly
disrupted by vessel interactions. The addition of one of more vessels during an
encounter further disrupted diving.
Responses of Hector’s dolphins to swim attempts were assessed from commercial
tourism vessel trips (n = 420). The method of approach and swimmer placement
affected the dolphins’ behaviour, with a reduction in avoidance when regulations were
adhered to, i.e. using line abreast and around methods. Dolphin responses to swim
encounters were also correlated with the number of successive attempts, dolphin
group size and initial behaviour. Although Hector’s dolphins appear to be more
tolerant of the presence of swimmers over time, some level of sensitisation to
seasonally high levels of vessel interactions was also detected. The effects of swim
encounters could potentially be exacerbated by the use of stones as an auditory
stimulant. Specifically, swimmers who used stones had a greater probability of close
and sustained approaches by dolphins than those who sang or simply floated on the
surface of the water.
Based on opportunistic photo-identification surveys (n = 254), 46% and 44% of the 50
identifiable individuals were infrequently and occasionally recorded interacting with
commercial tourism vessels, respectively. It was also estimated that individuals using
Akaroa Harbour are exposed to the highest level of cetacean-based tourism in New
Zealand. This implies that dolphins that are frequent users of the harbour are likely to
be more exposed to intensive tourism pressure. The high resighting rate of some
individuals further suggests that frequent users are unlikely to discontinue using the
harbour, even though they face increased human disturbance.
Data presented here reveal the nature and the susceptibility of Hector’s dolphins to
tourism activities, warranting the continuation of a moratorium on new permits.
Furthermore, a reduction in daily trip numbers should be considered. Ongoing
monitoring of this population’s response to tourism activities, combined with an
integrated and adaptive approach to management, gives the best chance of ensuring
the sustainability of the industry.