Carcasses of 23 dolphins found in Amazon town lakes
Researchers from the Federal University of Amazonas (Ufam) have found 23 carcasses of pink river dolphins and tucuxis in lakes in Coari, Amazonas state. The municipality borders Tefé, where more than 150 animals have died since September. Most of the carcasses were in an advanced state of decomposition.
A report released Friday (Oct. 27) by the Mamirauá Sustainable Development Institute, the Chico Mendes Biodiversity Conservation Institute (ICMBio), and Ufam states that most of the carcasses are of pink river dolphins, as was the case in Tefé, adding that samples of the dead animals are being collected for analysis in a bid to understand the cause of the deaths. The high temperature of the water is seen as the main hypothesis.
“In addition, water temperature sensors are being installed, and water samples have been collected,” the document reads.
In Tefé, researchers from the Mamirauá Institute continue to monitor the pink river dolphins and tucuxis in lake Tefé, as well as its water. Teams of professional volunteers are assisting the monitoring activities and taking turns with local researchers.
“With the level of the lake still very low, there is still a chance that the temperature of the lake’s water will rise again, much to the detriment of the animals living there. Over the last few days, the water temperature at monitoring point P1 has remained high at between 36 and 37.7°C,” the report notes.
Causes
To prevent further deaths of dolphins in warmer portions of lake Tefé, the researchers set up an isolating cordon to lead the dolphins to deeper areas of the lake, where the temperature is lower.
Even though the high temperature remains the most likely cause, the experts are not ruling out other possibilities—like water contamination or diseases in the animals. In addition to the high temperatures measured in the lake in the afternoon, there is also a wide variation in water temperature during the day, ranging from 28°C to 38°C on a daily basis.
“We have had 17 individuals evaluated with histological analyses and so no evidence has been found of an infectious agent as the primary cause of mortality. The molecular diagnosis (PCR) of 18 individuals also gave negative results for the infectious agents Morbillivirus, Toxoplasma, Clostridium, Mycobacterium, and Pan-fungal, associated with mass deaths,” the text reports.
