Science: Sophisticated Polynesian fish ponds fed a dense population on Hawaii
Scientists hope to recreate Polynesian food ingenuity on Hawaii. Will Harvie reports.
Polynesians on Hawaii developed elaborate aquaculture and agricultural systems, including fish ponds, that fed a dense population before European arrival, a visiting scholar said.
"They were a sustainable way of creating food for the population and quite a beautiful engineering design," said Dr Kiana Frank, an assistant professor at the Pacific Biosciences Research Center at the University of Hawaii, Manoa. She visited New Zealand recently.
Fish ponds were constructed in estuaries. Dykes built of rock and earth enclosed part of an estuary and sluice gates allowed fresh and salt water – and the nutrients they carried – to enter and exit with the tides.
The gates also allowed young fish, especially mullet, to enter the ponds and eat micro-organisms that the Polynesians encouraged.
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Fish could not escape through the narrow gates, due to clever design. They grew to maturity and were harvested, although some were allowed to bolt out to sea to grow further and breed.
These ancient Hawaiians "actively manipulated" the flow of nutrients from either fresh or sea water by combining detailed phenomenological observation with prudent land management, Frank said.
Estimates put the Hawaiian population before the arrival of Captain James Cook in 1778 somewhere between 200,000 and 1 million. In 2015, the Pew Research Center estimated there were 683,000 native Hawaiians when Cook arrived.
Te Ara, the Encyclopedia of NZ, puts the Maori population at about 80,000 at 1841.
If population estimates are uncertain or wrong, the size of each island group is not. Together all of the islands of Hawaii amount to 16,636 square kilometres, while New Zealand is 268,021 sqkm.
So the Hawaiian population density was much higher and the Polynesians there needed advanced food systems to survive, Franks said.
Considerable knowledge has been lost, however.
It's believed about 488 fish ponds were in production across the Hawaiian islands, but only 14 remain.
Most were filled with sediment as farming practices changed inland after the arrival of Europeans.
"There's a big movement in my community to deconstruct the knowledge that our ancestors captured," Frank said.
This included the microbiology of the fish ponds – Frank's field and one of her research interests – as well as archaeology, marine and fish sciences, and the lore handed down in poems, chants and traditional knowledge, she said during an interview at the University of Canterbury's Aotahi School of Maori and Indigenous Studies.
"Countless generations of data are stored in our 'oleo noʻeʻau (wise sayings)," she wrote. For example, pala ka hala momona ka wana translates to "when the hala (fruit) is ripe, the urchin is fat".
Other sayings include "when the sugarcane flowers, the squid comes forth" and "when the wiliwili tree blooms, the shark bites".
Franks believes these direct observations can help contemporary researchers understand pre-contact Hawaiian estuaries and seas. "As a scientist, I'd like to use contemporary tools and science to understand these stories and names," she said.
"I am very passionate about bridging science and indigenous culture (because to me, they are one an the same) and elevating the level and perception of 'science' in the community by engendering indigenous scientists that have deep connections to their place and the kuleana to protect them," she wrote. Kuleana can be roughly translated as responsibility.
As a microbiologist, Frank is collecting water samples from fish ponds and running "census" tests to "see what's there, what it's doing and how fast".
"This research provides a data-rich context to support and evaluate Native Hawaiian methodologies for restoring fish ponds," she wrote
In time, she hoped to return the the fish ponds' microbiology to pre-contact shape – or something close – which would assist with the ponds revival.
She has also spent time understanding indigenous cropping systems, another method that pre-contact Hawaiians used to feed a dense population. Often upland from the sea, these systems were highly productive, not reliant on external inputs, and required little or no fallow periods.
It's thought they used a sophisticated system of companion planting to maintain production, she said.
Hawaiians had intensified cultivations on virtually every area with adequate soil fertility, she wrote.
Franks got her PhD in molecular cell biology from Havard, where her research focused on microbial activity in undersea hydrothermal vents, which may be "analogs of the first living systems to evolve on Earth and ecosystems on other planets".
She jests that her education and work have taken her from ocean depths to the coast to the sides of volcanoes.