Abstract
Cetacean tourism has grown rapidly over the preceding decades, requiring careful and considerate management. Akaroa Harbour, Aotearoa New Zealand, is a core use area for Hector’s dolphins (Cephalorhynchus hectori) at Banks Peninsula, where this endangered and endemic species has been studied intensively since 1984. Here, Hector’s dolphins are exposed to some of the highest levels of tourism in New Zealand, including dolphin watching, swim-with-dolphin, cruise ship, and recreational vessel traffic. I analysed 2,335 sightings from 8,732 kilometres of survey effort via kernel density estimation to determine hotspots for dolphins within the harbour and assess stability in distribution over twenty years. A clear, southward shift in distribution occurred between 2005 – 2011 and 2012 – 2015, coinciding with a fourfold growth in annual cruise ship visits to Akaroa Harbour following the 2011 Canterbury earthquakes. The spatial overlap in core habitat between these two periods was just 24% and sightings rate analyses provided further evidence of a distributional shift in correlation with levels of cruise tourism. In order to quantify potential anthropogenic drivers of dolphin distribution, I developed and tested a novel, cost-effective, autonomous monitoring method to accurately quantify fluctuations in vessel traffic at Akaroa during summer 2019 – 2020. This time-lapse camera methodology, in combination with satellite tracking of commercial vessels, proved capable of accurately tracking relative levels of vessel traffic at multiple time scales. 59,296 images were analysed, accurately estimating fluctuations in vessel traffic (highest around midday, on weekends, and in January), total levels of vessel traffic in core dolphin habitat (mean = 40.51 vessels per day), and vessel speed in still images. Dolphin tourism trips composed a significantly larger proportion of vessel traffic during 2019 – 2020 than observed during 2005 – 2008, with generalised additive models (GAMs) revealing cruise ship presence directly led to more such trips. The effect of vessel traffic parameters on distribution during 2019 – 2020 was investigated using a moored passive acoustic recorder at a dolphin hotspot. GAMs revealed that increasing motor vessel traffic, cruise ship presence, and high levels of dolphin tour vessel traffic led to decreases in daily dolphin detections. Findings suggest that Hector’s dolphins at Akaroa have been displaced from core habitat over both short and long time scales in relation to tourism parameters. It must be asked whether cumulative human pressures on the harbour environment have reached unsustainable levels for this taonga species. Future research is warranted to investigate relationships between tourism and population parameters. Management should act with precaution using available tools.