Testing for toxins in kaimoana

Dr Dave Taylor of the Cawthron Institute in Nelson explains how concern from iwi over the discovery of tetrodotoxin in grey side-gilled sea slugs has led to further research – testing for toxins in kaimoana. Dave outlines how samples were tested on the Coromandel Peninsula and tells us how tetrodotoxin has been detected in small doses in pipi.

Transcript

DR DAVE TAYLOR
Further research that’s developed from the discovery of the toxin in sea slugs has been based around the concerns that these toxins might get into kaimoana that people collect off beaches in New Zealand. So with our research partners the Hauraki Māori Trust Board, we put a research proposal to Ngā Pae o te Māramatanga to look at the risks to kaimoana from these toxins that are in the sea slugs. In doing that, we set out to take samples from sites on the Coromandel to test for toxins or this tetrodotoxin in particular.

We collect samples in a number of different ways. First of all from different places on the shore, whether it be in the intertidal area and also subtidally, so we have to dive sometimes to get samples. We also try and trap different types of seafood for testing for this tetrodotoxin.

The testing has been going on for a year now, and we’ve been taking samples monthly from two sites on the Coromandel Peninsula – one on the east coast and one on the west coast of the Coromandel Peninsula – and our sample collector Dave Hamon has been sending those samples down to Cawthron for testing monthly. And initially for the first couple of months, everything came back negative for tetrodotoxin. Then after a while, we started getting trace amounts of the toxin in pipi from one site on the Coromandel at Whangapoua. 

And that of course initially raised some alarm bells with us, so we wanted to check that those results were significant, and so we had multiple samples sent up for the following months. And those also tested positive, so we then started informing people that care should be taken when collecting pipi from Whangapoua.

Tetrodotoxin has never been found in a bivalve before, and of course because people do eat pipi, it is of some concern. The levels are however extremely low, so you would have to eat about 5 kilograms of pipi flesh to die, which is a lot of pipis. So while we told people to exercise caution, we don’t think it’s a particular risk to humans.

Obviously the local iwi on the Hauraki Peninsula have been informed, and they are concerned that this toxin is in the pipi. There is some anecdotal evidence that this may have occurred before. So they understand that there are times when pipi might need to be avoided or eaten in low amounts.

Acknowledgements:
Wildfish Export Ltd
Destination Northland
Crown copyright, Department of Conservation
Hauraki Māori Trust Board