Massive Fishery Resurfaces in Amazon.

An aerial view of part of Bolivia's Amazon features a curious network of zigzag and straight lines cutting across floodplains. A close-up view reveals the lines to be the remains of an earthworks project that includes a fishery operated by native peoples of the Baures region before Spanish conquest, a new study finds.

The discovery casts light on engineering and environmental know-how that originated among Amazonian groups at least several thousand years ago, proposes Clark L. Erickson of the University of Pennsylvania in Philadelphia.

"The people of Baures converted much of the landscape into an aquatic farm," Erickson contends. "Rather than domesticate the species that they exploited, [they] domesticated the landscape."

It took ingenuity and planning to build the 326-square-mile web of causeways and fish-catching devices, or weirs, Erickson reports in the Nov. 9 NATURE. The weirs trapped fish that migrated to and spawned in the savanna during seasonal flooding.

Inhabitants of the region also dug large holes near the fish traps to store water for the dry months, Erickson says. These artificial ponds contained fish, attracted game, and nurtured palm trees that bore edible fruit, he proposes.

Native South American groups still build fish weirs, although they usually construct them in year-round bodies of water. The savanna structures studied by Erickson are longer, more numerous, and more densely packed than modern fish weirs. Radiocarbon dating puts some bits of burned wood from the weirs at 300 years old, providing a minimum age for the earthworks.

The Baures weirs are 3-to-6-feet wide, with earthen sides rising 7 to 20 inches. Every 30 to 100 feet, the channels bend in a sharp angle that contains a funnel-like opening. Several prehistoric Baures communities may have used interconnected fish weirs and causeways for water management as well as fish catching, Erickson suggests.

The Baures fishery adds to prior South American evidence of prehistoric irrigation canals, dams, and dikes, comments anthropologist Peter Stahl of the State University of New York at Binghamton.

Fish farming and root-crop cultivation (SN: 10/28/00, p. 280) are prehistoric practices that might be adapted to tropical areas today in place of "reckless felling of the rainforest," remarks Warwick Bray, an independent archaeologist in Herts, England.