Monday June 22, 2009

Weirs have long been used as a means to collect fish by indigenous people throughout North America. Recently, archeologists discovered a large rock tidal weir used to harvest fish on the receding tide.  More remarkable, archeologists are currently studying perhaps the largest fish weirs ever constructed, and what researchers have described as a “vast network of fish weirs, ponds, canals, and causeways to harvest fish and other aquatic resources.”  Some believe the ability to harvest and rear fish may have supported a large human population in the Amazon, much larger than without these capabilities, and much larger than previous believed existed.
The artwork in the beginning of this video is an attempt by the research team to accurately depict the people and landscape more than 300 years ago. The second part of the video shows a fish biologist cleaning a more modern Alaskan Weir, which is used to monitor anadromous fish, such as salmon and steelhead. Alaskan Weirs are a means of sampling fish without blocking the river, since the weir collapses under the weight of boats and other watercraft, allowing them to pass freely over the top. An underwater camera photographs each fish that passes the weir during clear water conditions, and an infrared camera scans each fish during turbid water conditions.
Earthmovers of the Amazon Charles C. Mann
Photographs by Clark L. Erickson. Painting by Dan Brinkmeier.

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