Decline of fruit-loving tambaqui fish could damage Amazon forests

By Lewis Smith
March 23 2011
The dramatic decline of a fruit-eating fish reputed to be among the most delicious freshwater species in the world could have severe consequences for the health of the Amazonian forests, researchers have found. Tambaqui, which have slumped by 90 per cent since the 1970s because of overfishing, have been found to disperse seeds a greater distance than almost any other animal. Experiments in Amazonian flood plains with radio-tracked tambaqui, which can grow to more than 3.5 feet long and weigh more than 88lbs, showed that they can deposit seeds almost 3.4 miles (5.5km) from where they were swallowed. Only the Asian elephant and the African hornbill have been shown to be able to transport seeds further in their guts than the South American fish. The bird and the elephant take them about four miles (6.5km). The fish is able to take the seeds long distances because it holds them in its gut for long periods, typically two or three days and up to 12 – by contrast, seeds can pass through the hornbill in a matter of minutes. But the slump in numbers of the tambaqui, Colossoma macropomum, reduces its ability to deposit seeds and it is feared the consequence will be to damage the range, distribution and genetic variety of plants in the Amazonian wetland, especially trees and lianas. “We don’t really know what the role of the fish is, relative to the other seed dispersing species, but my guess is they are very important in maintaining diversity,” said Dr Jill Anderson of Duke University, in the US. “They could be really important in structuring this community.” … During the 1970s tambaqui were so numerous that they were an “extremely commercially important” species in the Amazon and in the Manaus fish market in Brazil they comprised up to 40 per cent of all the fish on sale. In the last 40 years, however, tambaqui populations have fallen by 90 per cent. The average size has also fallen, with further potential to “compromise long-distance seed dispersal” because, the study showed, the bigger fish are able to transport seeds further. …