An international team of scientists has discovered that a large, commercially important fish from the Amazon Basin has become extinct in some local fishing communities. The team compared mainstream bioeconomic theory -- which policymakers have depended on in order to protect fish populations -- with the lesser-known "fishing-down" theory, which predicts that large, high-value, easy-to-catch fish can be fished to extinction.

"Bioeconomic thinking has predicted that scarcity would drive up fishing costs, which would increase price and help save depleted（耗尽的） species," said study leader Leandro Castello, an assistant professor of fisheries in Virginia Tech's College of Natural Resources and Environment. "If that prediction were true, extinctions induced by fishing would not exist, but that is not what has happened."

The research was conducted with arapaima（巨滑舌鱼）, a 10-foot long fish that can weigh more than 400 pounds.

"Arapaima spawn on the edges of floodplain forests and come to the surface to breathe every 5 to 15 minutes, when they are easily located and harpooned（用鱼叉叉） by fishers using homemade canoes," said Caroline C. Arantes, a doctoral student in wildlife and fisheries science at Texas A&M University and an expert on fish biology and fishery management.

The giant fish dominated fisheries in the Amazon a century ago, but three of the five known species of arapaima have not been seen for decades, said Donald J. Stewart, professor in the College of Environmental Science and Forestry at the State University of New York at Syracuse, who recently discovered a new species of arapaima.

The research was based on interviews with 182 fishers in 81 communities who were selected by their peers as being experts and on fish counts in 41 of the fishing communities, accounting for 650 square miles of floodplain area.

The results indicate that arapaima populations are extinct in 19 percent of communities, depleted (approaching extinction) in 57 percent, and over-exploited in 17 percent.

The results are reported this week in the journal Aquatic Conservation: Freshwater and Marine Ecosystems.