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Teina Rongo’s theory of migration

Monday November 20, 2017 Written by Published in Local
Dr Teina Rongo and Susan De Love Miguel of the National Museum discuss the display of ancient fi sh hooks discovered in Aitutaki. 17111020 Dr Teina Rongo and Susan De Love Miguel of the National Museum discuss the display of ancient fi sh hooks discovered in Aitutaki. 17111020

Having had a nasty bout of ciguatera poisoning for the seventh time, you’d think Dr Teina Rongo would have learned his lesson once and for all about eating reef fish.


The problem is, he has a real penchant for eating a variety of the gilled delicacy - grouper, snapper, mullet and trevally, among other reef fishes.

With no known cure, the symptoms of ciguatera poisoning alone are enough to put you off trying to achieve your daily intake of Omega-3. Victims suffer from neurological symptoms such as hallucinations and nightmares and just about everything else - from itching to paralysis and cardiovascular complications.

Then there’s the gastrointestinal problems, such as diarrhoea and vomiting. Severe cases of ciguatera can lead to death.

All you can do to get over it, he says, is rest up with “supportive treatment”, such as a saline drip in hospital if necessary, natural herbal remedies, or, you can simply “get over it”.

At least getting sick all those times has paid off. It has resulted in Rongo’s ground-breaking research proposing a link between ciguatera poisoning to the great Polynesian migration around 700-1000 years ago to colonise the far reaches of the Polynesian triangle from Hawai`i, Rapa Nui (Easter Island), to New Zealand.

It’s all part of a wider body of research that links ciguatera poisoning in the Cook Islands and climate variability that favours cyclone formation and other reef disturbances.

Since he first donned a cap and gown back in 2011 to receive his Ph.D. from the Florida Institute of Technology in Biological Sciences (Marine Biology), Rongo has received world-wide recognition for his findings.

Recently, he addressed a small gathering at the National Museum, following their display of 800-year-old fish hooks discovered in Aitutaki.

Rongo’s publication in 2009 suggested that even centuries ago, people learned through trial and error which fish were higher risk for ciguatera poisoning. And archaeological evidence of their dietary transition from larger predatory reef fish species to smaller fish. And shifts in associated fishing technology to catch these species, such as the pearl-shell fish hooks on display to weaker shell hooks made out of Turbo snail (ariri) also found in the middens. This suggests, he says, that people were attempting to avoid contracting ciguatera poisoning.

The presentation was also streamed on Facebook live for many more people to tune into his interesting theories.

“The great voyaging that ended up colonising New Zealand, Hawai`i and Rapa Nui came from theories which ranged from warfare, resource overexploitation, advances in canoe technology and climate change among others,” he says.

But none examined factors that may have affected the main source of protein for Polynesians, which is fish. It is important to find and understand ciguatera in the past, because it can help us understand the problem today. 

“I also looked into archaeological evidence and found indications of ciguatera poisoning happening during the period of the great Polynesian migration. If you take away fish from the diet, there are limited alternatives for protein, especially on atoll islands which are the most dominant island formation in the eastern and central Pacific.”

At any rate, Rongo says, ciguatera is as old as time, and even Captain Cook documented it during his travels.

He says centuries ago, his forefathers were skilled at traditional navigation and voyaging. And Rongo says it was just as easy as Cook Islanders today carrying a New Zealand passport and taking off in a jet whenever they want. He says his ancestors could pack up and leave in their canoes just as easily.

So what is the link between a cyclone event and the cause of ciguatera poisoning?

Rongo says that there is strong correlation between ciguatera and climatic cycles such as the El Niño Southern Oscillations (El Niño and La Niña). He found that the incidence of ciguatera increased during a period when El Niño events were high during the 1990s to mid-2000s in the southern Cook Islands, and this link is largely the result of higher frequency of reef disturbances from coral bleaching and especially cyclones. These disturbance events open space for the opportunistic microscopic plant responsible for the production of ciguatera toxins to establish.

However, during a La Niña period, fewer fish were poisoned. This was because reef disturbances were fewer as there were fewer cyclones and other associated events that open reef space.

Rongo suggests that 700-1000 years ago, similar climatic conditions were prevalent that would have caused ciguatera, prompting that major exodus south to New Zealand recorded in Polynesian history.

In recent times, most of the serious cases of ciguatera poisoning in the Cook Islands have been reported in Rarotonga and Aitutaki. Consequently, around 71 per cent of the resident population has excluded fish from their diet, particularly reef fish, says Dr Rongo.

“We have seen an increase in consumption of pelagic fishes (eg tuna) which are not affected by ciguatera poisoning. Since pelagic species are expensive, people from the lower income bracket of the population are not able to afford them.”

Rongo has also linked ciguatera fish poisoning to the depopulation of Cook Islands in modern times, particularly around the 1990s when ciguatera poisoning was at its peak.

“During this time, a large number of people migrated to New Zealand and Australia due largely to the financial crisis that the country was going through. But if you look at the people that moved away, particularly from the lower income bracket of the population, this was the group of people that relied heavily on marine resources to supplement their diet.”

At the same time, Dr Rongo’s study showed a shift away from a seafood diet generally in Cook Islands.

“Prior to ciguatera poisoning there was a lot of seafood in the diet of residents. But when ciguatera was at its height, there was a shift away from seafood towards imported goods – a trend that has continued to present day. Some people don’t even touch fish anymore,” says Rongo.

He adds the Cook Islands is entering a period where the climate is oscillating toward a situation unfavourable for the establishment of the organism that causes ciguatera poisoning.

This climate cycle is called the Pacific Decadal Oscillation, which has two phases – positive and negative, that shifts every 15 – 30 years. The positive phase gives rise to a higher frequency of El Niño events where the probability of cyclone formation and coral bleaching is high, while the negative phase linked to more La Niña events brings the opposite effect for the southern Cook Islands.

“We have entered into the negative phase, meaning more La Niña events that would bring conditions not conducive to the growth of ciguatera organisms.”

This is evident in hospital records, as cases of ciguatera have continued to decline to an all-time low in the southern Cook Islands since the five major cyclones in 2005.

Over a decade ago, Rongo felt a calling to study the disease that was pervading his “playground”, Rarotonga’s reefs.

He says he grew up in a family that did a lot of fishing, and in primary school he’d rush home to get on the reef with other kids in the community and fish for small groupers. But when ciguatera became prominent, he says his playground was being abandoned.

He watched as kids started to turn away from fishing as a pastime and eating fish as a dietary staple, in doing so losing the traditional knowledge critical for managing marine resources.

Rongo divides the population into two groups, which he terms the pre-ciguatera generation and the ciguatera generation. The ciguatera generation, he says, didn’t grow up eating fish and didn’t acquire a taste for it, and did not grow up comprehending the value of the resource.

“I wanted to understand ciguatera so I could help our people return to fishing as a way of life in the face of climate change as well as pressures to develop our nation for economic gain. Traditional fishing in a sustainable way helps us reconnect to our environment to foster the appreciation and valuing of our resources, which leads to better management strategies,” he said.

So he embarked upon a decade’s worth of study, first earning a Bachelor’s and then a Master’s at the University of Guam, and reaching the culmination of his study with a doctorate degree.

Rongo’s Ph.D. dissertation was focused on ciguatera and what triggers it in the Cook Islands, how it features in Cook Islands history, and its wider socioeconomic implications.

Rarotonga is said to have had the highest number of ciguatera cases in the world and that’s just what the record reflects. Seventy percent of cases are not reported to medical authorities.

Rongo says when ciguatera was at its peak, it cost the Cook Islands economy around $1.5 million per annum in losses, including lost revenue from fish sales.

Rongo’s research also examined areas of Rarotonga lagoon which are most likely to host ciguatera carriers. Although ciguatera was reported from all locations around Rarotonga, he found that wider lagoons like those in Nikao, Ngatangiia, and Titikaveka that are not as prone to considerable water movement provided the ‘ideal’ environment for ciguatera-carrying organisms to settle comfortably on the reef.

“The organisms are opportunistic and they’re not good competitors”, he says, “They need disturbance events to clear the way for them.”

People tend to blame land-based activities like pig farming for causing the proliferation of ciguatera, but Rongo says nutrient run-off is not the likeliest culprit.

While he does not discount this claim, he admits it is as yet unsupported in the ciguatera literature.

“In the past, people had more pigs because they were living subsistence lifestyles. Every house had a pig tied up next to the stream. Today you don’t find this to the scale of the past.”

Rongo says the decrease in ciguatera could lead to one of two socioeconomic situations - either the ciguatera generation has shifted so far away from subsistence living that it will not re-adjust, or people will return to fishing and put pressure on the resource.

He says the danger of the latter situation is that greater numbers of people will target the fish species that have been determined through trial-and-error least likely to carry ciguatera. Overfishing certain species, of course, has the potential to upset a finely-balanced ecological system.

 “We need to manage our fish resources better,” he said.

“We seriously need to raise the awareness of our marine issues in the community and especially among our youth. Perhaps teaching the ciguatera generation how to fish again using our traditional fishing methods that are proven sustainable and environmentally friendly will reconnect them to their environment, and increase their appreciation of their resources. 

“There has been a noticeable decline in reef fish recruitment along with coral reef health throughout the Cook Islands in the last few decades, and climate change impacts are exacerbating the problem. Efforts that lead to better management of our marine resources is far more important now than ever.”

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