A long‐term shift in the summer distribution of Hector’s dolphins is correlated with an increase in cruise ship tourism

Abstract

Before the 2020 COVID‐19 pandemic, cruise ship tourism had been one of the fastest growing segments of global tourism, presenting a range of potential impacts. At Akaroa Harbour, Aotearoa New Zealand, the number of annual cruise ship visits more than quadrupled following earthquake damage to Ōtautahi Christchurch's Lyttelton Port in 2011. Akaroa Harbour is an area of core use for endangered and endemic Hector’s dolphins (Cephalorhynchus hectori). Dolphins here are exposed to some of the highest levels of cetacean tourism in Aotearoa New Zealand. Relationships were examined between growth in cruise ship visits, as well as tours focused specifically on dolphins, and long‐term trends in summer distribution of Hector’s dolphins at Akaroa Harbour, from 2000 to 2020. Core use areas for Hector’s dolphins within the harbour were quantified via kernel density estimation using data from 2,335 sightings from over 8,000 km of standardized survey effort. Data were allocated into four periods based on varying levels of tourism. Dolphin habitat preference varied over time, with the greatest change occurring between 2005–2011 and 2012–2015. When comparing these periods, the spatial overlap of core habitat was less than 24%. Dolphin distribution shifted towards the outer harbour after 2011 and has remained relatively consistent since. The observed shift in distribution coincided with the more than fourfold increase in annual cruise ship visits to Akaroa Harbour. Several pressures related to cruise ship tourism are likely to have influenced habitat preferences of dolphins. Further investigation into causal factors of the observed shift is warranted. In the wake of the COVID‐19 pandemic, the future of cruise ship and wildlife tourism is in flux. Our findings suggest that the future re‐development of this industry should follow a precautionary approach, with the onus on industry to provide evidence of sustainability before proceeding.

Vessel traffic influences distribution of Aotearoa New Zealand's endemic dolphin (Cephalorhynchus hectori)

“…Increased cruise, recreational, and dolphin tourism traffic resulted in fewer dolphin detections at Nine Fathom Point. These results support the hypothesis that the influx of cruise ships, and related increases in tourism, have contributed to a shift in dolphin distribution observed during the last decade (Carome et al, 2022). Dolphins may be shifting from areas of importance for foraging (e.g., Brough et al, 2020) to inferior habitat during times of high vessel traffic.…”

“…Additionally, habitat-related variables, such as current profiles or substrate, were also controlled for in this sampling regime. Nine Fathom Point is at the northern extreme of contemporary core habitat for dolphins at Akaroa Harbor (Carome et al, 2022), suggesting that displacement to more suitable habitat would be southward. Furthermore, extracting characteristics of dolphin clicks, such as frequency of foraging buzzes (Brough et al, 2020), could further elucidate potential impacts of vessels on these dolphins.…”

“…Furthermore, Akaroa experienced a more than fourfold increase in annual cruise ship visits during summer 2011-2012, following earthquake damage to Otautahi's Lyttelton Port (Wilson et al, 2015). The influx of cruise passengers extended the peak tourism season and is correlated with a shift in distribution of Hector's dolphins during the last decade (Carome et al, 2022).…”

Finite mixtures in capture–recapture surveys for modeling residency patterns in marine wildlife populations

“…Changes in the presence of such dolphins in an area may reflect changes in driving features such as habitat quality, prey distribution, or anthropogenic disturbance. The year 2020 was the COVID‐19 pandemic, with changes in ecological conditions and human pressures on coastal marine waters (Carome et al., 2022). Although difficult to assess, the influence of these factors on the number of transient individuals cannot be ruled out, as several dolphins may have been induced to reduce their mobility toward the study area by improved conditions in their native habitat.…”

A Quieter Ocean: Experimentally Derived Differences in Attentive Responses of Tursiops truncatus to Anthropogenic Noise Playbacks before and during the COVID-19-Related Anthropause

“…While the dolphins tested in our study sought out the anthropogenic noise source, not all dolphins respond similarly. The increased presence of cruise ships over a decade have shifted Hector’s dolphin ( Cephalorhynchus hectori [ 74 ]) distributions towards the dolphin’s normal outer habitat away from the inner harbor where cruise ships dock [ 75 ]. This may be due to the presence of cruise ships themselves more so than the noise levels.…”