Sept. 16 (UPI) -- Aquaculture has deep historical roots in China. New analysis of ancient fish bones suggest humans in China were managing carp aquaculture as long as 8,000 years ago.
Scientists published their findings this week in the journal Ecology and Evolution.
There is historical evidence of carp farming. The Shijing, the oldest existing collection of Chinese poetry, describes carp being raised in a pond as early as 1140 BC. Other East Asian historical records mention carp being reared in artificial ponds and paddy fields during the first millennium BC.
When scientists discovered fish bones at an Early Neolithic Jiahu site in Henan Province, China, they suspected the carcasses evidenced an aquaculture operation. The archeological site has previously revealed evidence of rice and pig domestication, as well the early development of fermented beverages and bone flutes.
For the latest research, scientists analyzed the body-length distributions among the hundreds of fish fossils recovered at the Early Neolithic Jiahu site. Scientists found different fish fossil collections corresponding to different Neolithic periods. The researchers compared the body-length distributions from each period to one another, as well as to the body-length distributions among modern carp raised in Matsukawa Village, Japan.
The distributions of the later two Neolithic periods showed a single unimodal pattern of body-length distribution peaking close to carp maturity. In other words, the bones suggest the fish were farmed and then harvested when the fish were fully grown.
The fish bones from the earliest Neolithic period, dating from 6200 to 5700 BC, revealed a different pattern, one with two peaks -- a bimodal distribution. The first peak corresponded with sexual maturity and the second correlated with physical maturity.
"In such fisheries, a large number of cyprinids were caught during the spawning season and processed as preserved food," researchers wrote in the journal Nature. "At the same time, some carp were kept alive and released into confined, human regulated waters where they spawned naturally and their offspring grew by feeding on available resources. In autumn, water was drained from the ponds and the fish harvested, with body-length distributions showing two peaks due to the presence of both immature and mature individuals."
Scientists also analyzed the species distribution among the ancient fish fossils. Despite its name, the common carp is usually outnumbered by crucian carp in East Asian lakes and rivers, but at the Early Neolithic Jiahu site, researchers found more common carp remains than crucian carp bones.
Based on the latest findings, researchers hypothesized that aquaculture developed over the course of three stages.
First, Neolithic farmers began fishing marshy areas where carp gather during spawning season.
Next, farmers began managing the marshes by digging channels to influence water levels and circulation, allowing the carp to spawn and for juvenile fish to be easily harvested.
Eventually, the operation mandated total human management, including the construction of artificial spawning beds for reproduction, as well as the use of artificial ponds to rear adolescents.
Scientists have yet to find paddy fields at Jiahu, but researchers suspect the evolution of carp aquaculture was linked with the development of wet rice agriculture. The study's authors hope further research will reveal connections between the two systems of sustenance.