efe-epaBy Carlos A. Moreno Rio de Janeiro

Brazil successfully completed an Amazonian manatee reintroduction program in the past few days, releasing a record 12 of the aquatic mammals into the wild.

The Amazonian manatee (Trichechus inunguis), an endangered species, is the smallest species of manatee.

The operation marked the largest release of manatees into Amazonian rivers as part of a program to increase the species' numbers.

Amazonian manatees are found in the Amazon River and its tributaries in Brazil, Peru, Ecuador, Bolivia, Colombia, Venezuela and Guyana.

The animals released into the wild - five males and seven females - ranged in age from 3 to 16, weighed an average of 120 kilos (264 pounds) and measured up to two meters (6.5 feet).

The species, which is protected in Brazil, can weigh up to 500 kilos (1,100 pounds) and measure three meters (about 10 feet).

"The process of reintroduction into the wild was carried out completely successfully. The animals were released and we left a scientist in the region to conduct initial monitoring," a National Amazonian Research Institute (INPA) spokesman told EFE.

The manatees were released in the Piagaçu-Purus reserve, located about 173 kilometers (107 miles) from Manaus, the largest city in the Amazon and the site of INPA's headquarters.

The INPA had already reintroduced 23 manatees into the wild in the past 10 years, all of them at Piagaçu-Purus, which is located close to the headwaters of the Purus River.

Fishermen in the area have been trained to help protect the endangered species.

"With the latest ones, we have now released 35 animals in the reserve, which we are told are still alive and in the region, at least those wearing (radio transmitter) belts. Of the 12 (manatees) reintroduced on this expedition, four had belts," the INPA spokesman told EFE.

The animals were transported to the region last Friday aboard a ship equipped with three giant water tanks and released between Saturday and Sunday.

INPA personnel wrapped up the expedition on Monday after activating the radio transmitters that will allow scientists to track the manatees.

In 2008, the INPA implemented a program to rescue, rehabilitate and reintroduce Amazonian manatees into the wild.

The marine mammals are often injured when they are caught in fishing nets, and sometimes the animals are found in the possession of fishermen and poachers.

The 12 manatees released into the wild had been raised in special tanks at the INPA complex and had been rescued from poachers or following accidental captures, biologist Diego de Souza, who runs the reintroduction program, said.

"The rescued calves are rehabilitated in INPA's fiberglass tanks. Usually, these animals have lost their mothers to hunters or been left trapped in nets," Souza, a specialist on freshwater species, said.

Project coordinator Vera da Silva said the reintroduction program was essential for boosting the population of a species listed as "vulnerable" to extinction.

"These are tame animals that move slowly, making them easy targets for poachers. To restore the population of this species, which is very important for the balance of aquatic systems, we have been conducting the reintroduction program for 10 years," Da Silva said.

Amazonian manatees were hunted for decades for their skins, meat and oil.

Deforestation and environmental degradation in the Amazon have also affected the marine mammals' numbers.