A network of fish ponds supported a
permanent human settlement in the seasonal drylands of Bolivia more than
one thousand years ago, according to a new study published May 15, 2019
in the open-access journal PLOS ONE by Gabriela
Prestes-Carneiro of Federal University of Western Para, Brazil, and
colleagues. The study is the first to document the full range of fish
species likely kept in these constructed ponds, and provides new
insights into how humans modified the savannah environment to cope with
the months-long droughts that characterize this region of the Amazon
Basin.
The Llanos de Mojos region in central Bolivia is a vast plain which
receives flooding rains from October to April, and then virtually no
precipitation the rest of the year. Beginning about 500 AD, humans began
to create monumental earthen mounds in the region, on which permanent
settlements were established. One, called Loma Salavtierra, located more
than 50 kilometers from the nearest major river, has become an
important archaeological site. Previous work has established the
existence of a series of shallow ponds rimmed by low earthen walls and
connected by canals, which are believed to have captured rainfall and
stored it throughout the dry season, potentially built to serve multiple
purposes including water storage, drainage, and fish maangement.
In the current study, the authors conducted osteological and taxonomic identifications on the remains of over 17,000 fish found in midden piles at the site with the aid of a comparative collection. They identified more than 35 different taxa of fish, with four types of fish predominating: swamp-eels, armored catfish, lungfish, and tiger-fish, all of which are adapted to conditions of low oxygen and fluctuating water levels, as would be expected to arise in the ponds during the long dry period between annual rains.
Together with evidence of similar pond networks elsewhere in the region, the authors suggest that their results point to the use of these ponds for harvesting fish year-round, far from any rivers, permanent natural ponds, or other open-water habitat. Further studies will be needed to investigate fish storage and holding activities, and whether these activities changed in response to precipitation and landscape fluctuations.
The authors add: "The savanna, in contrast to the large Amazonian rivers, presents a distinct set of fishing habitats where humans likely established specific fishing strategies."
In the current study, the authors conducted osteological and taxonomic identifications on the remains of over 17,000 fish found in midden piles at the site with the aid of a comparative collection. They identified more than 35 different taxa of fish, with four types of fish predominating: swamp-eels, armored catfish, lungfish, and tiger-fish, all of which are adapted to conditions of low oxygen and fluctuating water levels, as would be expected to arise in the ponds during the long dry period between annual rains.
Together with evidence of similar pond networks elsewhere in the region, the authors suggest that their results point to the use of these ponds for harvesting fish year-round, far from any rivers, permanent natural ponds, or other open-water habitat. Further studies will be needed to investigate fish storage and holding activities, and whether these activities changed in response to precipitation and landscape fluctuations.
The authors add: "The savanna, in contrast to the large Amazonian rivers, presents a distinct set of fishing habitats where humans likely established specific fishing strategies."
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