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A 10ft (3m) long fish which used to dominate the Amazon river has been fished to extinction
in a number of areas, scientists have revealed. Arapaima populations were found to be extinct
in eight of the 41 communities studied, and extremely low on average.
Fishermen were trained to count the fish as part of a large-scale survey.
Researchers concluded that the effects of fishing on tropical fish was worse than previously
thought. Study results are reported in Aquatic Conservation:
Freshwater and Marine Ecosystems. Arapaima can weigh more than 28st 8lb (181kg)
and are among the largest freshwater fish in the world.
They are air-breathing and come to the surface every five to 15 minutes, making them easy
to catch. Their size means they are highly sought after
and are landed by fishermen using harpoons and gillnets.
A century ago the giant fish dominated fisheries in the Amazon but the researchers say overfishing
has dramatically reduced their numbers. Previously, bio economic theory predicted
that fishing does not cause extinctions because fishermen inevitably move away from depleted
resources. Scientists, led by Dr Leandro Castello, from
Virginia Tech, US, wanted to know how healthy the arapaima populations in the Lower Amazon
region were. They also wanted to find out whether these
fisheries supported bio economic predictions or the alternative fishing-down theory which
predicts that large, high-value, easy-to-catch fish will be fished to extinction.
The researchers interviewed 182 fishermen, who were considered to be "experts" on fisheries
by their colleagues, in 81 communities covering 401.5 square miles (1040 kilometres squared)
of Amazonia floodplains. Fish counts were also carried out in 41 of
those communities where interviews had been carried out. Eight fishermen were trained
to count the arapaima at the moment they surfaced for air.
The census revealed that arapaima populations were depleted in 57% of the survey area, locally
extinct in 19%, over-exploited in 17%, and well-managed in just 5%.
In 2% of the communities they were un-fished. In addition to the census results, more than
three quarters of the fishermen questioned said that arapaima numbers had decreased in
recent years. Almost a quarter of the fishermen in each
community fished arapaima regardless of the population's status.