Dear Marmamers, I’m happy to let you know that our new paper on the first genetic confirmation of a Hector’s dolphin in the northeast of North Island/ Te-ika-a-Māui Hector's dolphins in Aotearoa New Zealand is now published in Aquatic Conservation. We also summarise the other genetically confirmed instances of a Hector’s dolphins around the North Island, which is outside their normal range, and compare three different opportunistic sampling methods for collecting DNA for subspecies identification.
The paper is free to access here: https://onlinelibrary.wiley.com/doi/epdf/10.1002/aqc.70439 Below is a lay summary of the work. Genetics is the only way to tell the difference between a Hector’s and a Māui dolphin, as they are impossible to tell apart visually or acoustically. In 2023 and 2024, two Cephalorhynchus dolphin sightings occurred in the northeast Te-ika-a-Māui/North Island, well outside the known ranges of both Hector's and Māui dolphins. These sightings included a pair of dolphins, likely an adult and juvenile, in Tīkapa/Firth of Thames, Hauraki Gulf, and a solitary dolphin in the Waitematā Harbour, Tāmaki Makaurau/Auckland. Genetic analysis of the adult Firth of Thames dolphin confirmed it as a Hector's dolphin, and microsatellite genotyping assigned it with very high confidence (>99%) to the East Coast Te Waipounamu/South Island population, marking the first confirmed Hector's dolphin record in East Coast Te-ika-a-Māui/North Island waters. The Waitematā dolphin's subspecies could not be determined. Combined with eight previously identified Hector's dolphins sampled around the North Island, the results show these wandering individuals in the North Island originate from both the West Coast and East Coast South Island populations, rather than a single source. The study, led by the University of Auckland - Waipapa Taumata Rau and supported by the Department of Conservation - Te Papa Atawhai, also compared three opportunistic sampling methods. Skin biopsy sampling was the clear standout — it produced a full genetic profile of the Firth of Thames adult, making it the only method capable of pinpointing population of origin. Scrubby (sloughed-skin) sampling, taken from the juvenile Firth of Thames dolphin, yielded only a short, low-quality sequence sufficient to identify it as a Hector's dolphin. Seawater sampling for environmental DNA (eDNA) failed at both encounters, despite one sample being collected close to the adult dolphin. This contrasts with other studies where eDNA has worked well around larger dolphin groups. This underscores that biopsy sampling should be prioritised for extralimital sightings, as it remains the only reliable way to confirm both subspecies and population of origin, that is, information essential for conservation decision-making. Ngā mihi Emma Carroll
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