Stingrays in the Bay of Plenty

Stingray spotting in the Bay of Plenty


Next time you’re wandering down the Strand, around the wharves or at the Tauranga marina, keep your eyes peeled for stingrays. If you see one, research student Helen Cadwallader would love to hear about it.

Helen is mad about stingrays and is applying her knowledge to find out more about these largely un-researched, important marine creatures.
She is now one year into her PhD at Waikato University. And she is encouraging people in the Bay to get behind the research and report any stingray sightings. With the help of ‘citizen scientists’ – citizens who voluntarily support science research projects by reporting wildlife sightings – researchers can gather much more data and cover a more expansive area than they could as just a small team.

“Having the community’s help with sightings will make a huge difference to our monitoring programme,” she says. “The more data we can get, the better we’ll be able to understand how and if ray populations move in and out of the harbour and where they congregate.”

Impact of urbanisation

Helen, 28, is from Welshpool in Wales and has made Tauranga her home while she spends the next few years on her research. Her workplace is the busy Coastal Marine Field Station in Sulphur Point, home to the University’s marine and coastal research division.

She says while scientists have studied stingrays in remote marine habitats, so far very little is known about rays in urban environments and especially in New Zealand. Helen’s ground-breaking research will specifically look at the impact of urbanisation on ray populations.

“Our population is growing massively, especially in Tauranga, and this has a huge effect on the coastal and marine environment. We want to find out if coastal changes are having any effect on populations. If ray numbers decline, it causes a negative effect on other marine organisms. Rays provide food for orca and control carbon and nitrogen in the sediment. They’re a really important part of the harbour ecosystem.”

Helen will also take biopsies to check differences in rays from both the urban harbour environment and rural areas. She’ll be looking at levels of harmful chemicals. They may be higher in urban stingrays as a result of the time they spend in developed areas. Current monitoring shows low levels of heavy metals in sediment and molluscs – the preferred ray food source. But the effect of bio-accumulation (toxic build-up) in rays could be hiding a much bigger environmental problem. No research has yet investigated this in New Zealand.

Rays come from the same family as sharks – they evolved as a flat shark. But are more at risk of extinction than sharks. And we know a lot less about them. Like sharks, they are threatened because they grow slowly, mature late and have few young.

Discovering the unknown

Helen gets excited about rays and sharks in the same way other scientists are fascinated by bugs or black holes. As a child her family spent holidays at the coast where she loved exploring rockpools. So it was no surprise to her parents when she embarked on a biology degree in 2007.

“I love finding out about things nobody knows about yet. It really is discovering unknown territory and I love getting other people interested in what I’m doing. I’ve always been a shark and ray person, so I find the research fascinating, and I enjoy getting outside and doing hands-on science.”

In 2011 she spent three months in NZ volunteering in dolphin research before returning to Wales to complete her Masters degree in marine biology, specifically researching parasites in thresher sharks. She’s lived in Tauranga since the end of 2013, apart from a short working stint back home, and began her PhD last year.

Summer tagging

Starting in November, the next field season will involve tagging up to 50-60 rays during the summer, to track their movements. Do they stay in the harbour all year or do they move to and from deeper waters? And if so, why? Helen hopes to find answers to these questions during her research. She says that’s where the community can help out by reporting ray sightings.

Helen places two tags on each ray – one with a number on it. Ray spotters can go online to report the number (if seen) and colour of the tags, and location of the sighting. “Even if you see a ray without a tag, we still want to know about it, as this gives us more data about ray numbers and where they are congregating.”

Rays tagging in the Bay of Plenty

Helen aims to complete her PhD in early 2019, and has plans to stay in New Zealand and continue with post-doctoral research. “I love it here, and there is still so much research to do. This is a perfect location because of ray populations congregating in both the urban and more remote environments. It makes for a really good contrast.”

Report a Ray

If you see stingrays in and around Tauranga Harbour, researchers would love to know:

  1. Go to
  2. Report the tag colour, and number if you can see it.
  3. Report the location (if no tags, just report the location).

Thanks! Your report is helping scientists gather important data about stingrays in the Bay of Plenty.

Words Millie Freeman | Images Supplied + Savant Creative