This is the fourth blog in the Protecting ’Hector’s series – a deep dive into a collaborative research project trying to find out how we can coexist sustainably with this rare taonga species.
Tucked on the south side of Te Pātaka o Rākaihautū (Banks Peninsula) is the peaceful and unique Akaroa Harbour, home to the world’s smallest, and one of New Zealand’s most at threat dolphin species, the Hector’s dolphin.
DOC is working alongside local tour operators, Rūnanga, researchers and the regional council to study the impacts of cruise ships, dolphin tourism and general vessel traffic in the Akaroa Harbour.
Researcher Will Carome describes their methods for tracking boat traffic in Akaroa Harbour.
Latching the gate behind me I walked out past undulating paddocks of cattle and vegetation, as the view opened to the expanse of the iridescent Akaroa Harbour. Underneath manuka, kōtukutuku, and blue sky, I plodded along the Banks Peninsula Track to Nine Fathom Point to change the memory card and check the power supply of our automated camera.
A dolphin hot spot
Midway between Akaroa town and the open ocean, a sloping headland, sprinkled with sheep, manuka, and gorse, juts into the eastern margin of Akaroa Harbour. Multiple studies have shown the waters off this headland, known on nautical charts as Nine Fathom Point, to be important to Hector’s dolphins.
Our research group has found dolphins here more often than not for the last thirty years. While this hotspot has been stable, in our last installment we revealed that the distribution of dolphins has shifted southward during the last decade.
This shift suggests dolphins may have been displaced from previously important habitat, possibly related to levels of boat traffic. To test this hypothesis, we needed to accurately measure both vessel traffic and dolphin presence over time.
How does one measure a boat?
Previous research has tracked boat traffic at Akaroa Harbour using a theodolite, a surveyor’s instrument that can be used to determine the GPS position of objects in view. This requires a dedicated team and painstaking hours of watching, waiting, and fastidiously recording measurements. While it is a breathtaking view, spending days on the hillside was going to cost us valuable time surveying for dolphins on the water.
Which data was more important to collect? Fortunately, we didn’t have to choose.
We enlisted the help of a clever multiskilled expert at Otago University? Hamish Bowman, to develop a specialised camera system to keep an eye on the boat traffic while we were out looking for dolphins.
Counting boats in the digital age
We mounted a point-and-shoot camera in a weatherproof housing on a steel frame. Fueled by solar panels, a custom-built controller instructed the camera to capture an image from Nine Fathom Point every two minutes for all of summer 2019 – 2020.
Collaboration with DOC and the local tour operators also allowed us to collect high-resolution data on each dolphin tourism vessel from customised GPS tracking systems. This allowed for us to keep a close eye on the dolphins while automated computers kept watch of the boats… at least during field season.
Come March 2020, I returned to Dunedin with forty thousand photographs in tow while the camera kept snapping away through Lockdown. While some picked up baking or yoga during this period of isolation, I dug into counting and categorising boats. We’re not far off from training computers to do this for us, but for now these tasks rely heavily on graduate students.
Big data from a big dataset
Not only did we demonstrate the value of a new application of an automated camera system, but the data also gave us some really important insights. We observed an increase in dolphin tourism as a share of overall vessel traffic at Nine Fathom Point since 2008, with more tours on days with cruise ships in the harbour.
We were also able to infer that general traffic has likely increased at Nine Fathom Point, with over fifty boat trips on average passing each day in January.
Our observations at Nine Fathom Point suggest that pressure on the local dolphin population from boats, especially tour boats, has increased over time.
Might pressure from boat traffic, including dolphin tourism and cruise ships, be influencing where dolphins choose to be in the harbour?
To get closer to the answer, we put out a device programmed to listen for dolphins in the area. Tune in for our next installment to find out.