Food poisoning, not wanderlust, may have inspired early Polynesian wayfarers to undertake risky voyages across the Pacific to Hawai'i, New Zealand and Rapa Nui, according to new research.

Using archaeological evidence, prehistoric climate data and recent reports of ciguatera poisoning from the consumption of contaminated reef fish, researchers at the Florida Institute of Technology theorize that climate conditions conducive to ciguatera outbreaks may have occurred in French Polynesia between A.D. 1000 and 1450 — an active period of Polynesian voyaging and colonization.

"Notwithstanding the adventurous spirit of people of the distant past, we suggest that when ciguatera fish poisoning became chronic, people migrated out of necessity," said a study by Teina Rongo, a doctorate student at the university's Department of Biological Sciences, and his faculty advisers, professors Robert van Woesik and Mark Bush.

Heavy reliance on a fish-based diet makes Pacific Islanders particularly vulnerable to ciguatera poisoning, which affects between 50,000 and 500,0000 people annually in tropical and subtropical regions. It is estimated that up to 90 percent of cases go unreported.

In Hawai'i, where ciguatera is less common, 32 cases were reported last year, according to the state Department of Health.

Rongo, a Maori from Rarotonga in the Cook Islands, noted that modern-day ciguatera outbreaks resulted in mass migrations of Cook Islanders to Australia and New Zealand, including many low-income families that supplement their daily protein with fish.

"In fact, the theory originated from my experience in the Cooks, when I noticed families that I used to fish with growing up were relocating to New Zealand when ciguatera began in the 1990s, and fishing drastically declined while the consumption of imported goods increased," he said in an e-mail to The Advertiser. "Past populations did not have these alternative food sources, as ciguatera rendered their main source of protein inedible."

Fish become contaminated when they inadvertently ingest microscopic algae containing ciguatoxins. The toxins become progressively concentrated as smaller fish are devoured by larger fish, until they reach particularly high concentrations in large predatory reef fish such as barracuda, grouper, snapper, mullet, jacks, mackerel and triggerfish.

Humans who consume contaminated fish may suffer nausea, vomiting, diarrhea, excessive sweating, head-ache, muscle aches, weakness, itching, a "pins-and-needles" burning sensation and a reversal of temperature sensation. Ciguatera poisoning is rarely fatal and symptoms usually clear in one to four weeks, but can last for years.

Although the environmental factors affecting ciguatera poisoning are complex, Rongo and his fellow researchers believe they found a link between ciguatera events in recent decades and negative phases of the Pacific Decadal Oscillation — a pattern of climate variability in the Pacific Ocean with phases that persist from 20 to 30 years. A negative phase brings a cooler climate to French Polynesia favorable for ciguatera.

Studying data from ice cores and lake records from the Andes mountains in South America, coral cores and oceanic deposits, "we went back in time" and found such climate conditions likely occurred in the region between A.D. 1000 and 1450, Rongo said.

The climate factors coincide with archaeological evidence showing abrupt changes in fishing practices and dietary preferences in the post-1450 period, possibly in response to ciguatera events, Rongo said. Fish bones and hooks recovered from domestic waste dumps and excavations indicate that islanders were catching and eating fewer nearshore fish, which are at higher risk of ciguatera contamination, in favor of offshore varieties.

Rongo said his theory in no way diminishes the achievements of adventurous Polynesian voyagers.

"Polynesians were excellent wayfarers. Their superb navigational skills and advanced canoe technology would have made it easy for them to set out to discover new lands when ciguatera was encountered for the first time in French Polynesia," he said.

"We realize this theory is difficult to prove or disprove, however, in offering this perspective, we hope that it will be a stepping stone for other researchers, particularly in archaeology, to further examine the influence of ciguatera on the movements of past populations."

His study appeared online May 18 in the Journal of Biogeography.