Officials at the National Chambal Sanctuary (NCS) suspect that ghariyals came in contact with excess heavy metals when they consumed a fish called Kahawai, mostly found in Yamuna. The fishes entered Chambal from Yamuna as both the river meet in the Pachnada locality of the Etawah district, they added.

IVRI doctors maintained that winters usually reduce the immunity power of ghariyals. As there was a sudden drop in temperatures in December, their immunity power declined, resulting in their deaths, the doctors added.

Sources in the IVRI and NCS said that the dead ghariyals were above 10 years of age, and have therefore consumed heavy metals for a long time.

However, District Forest Officer, NCS, G Sudhakar Rao said: “We can’t confirm the reason behind the death of the ghariyals at this point of time. We are still waiting for reports from other centres.”

NCS officials had sent the fins of the dead fish found in one of the dead ghariyals for further tests. It has also sent samples of water and sand from both Yamuna and Chambal to IVRI for tests.

According to NCS officials, Yamuna contains heavy metals because of the presence of several factories on its banks in Agra and Ferozabad.

During the last two weeks, the NCS and the Madhya Pradesh government have recovered 52 dead ghariyals in the Chambal river area. According to official records, 30 of these ghariyals were recovered in Uttar Pradesh while 22 were found in Madhya Pradesh.

The death came under scrutiny after NGO Society for Conservation of Nature spotted two dead ghariyals near Chambal and informed the forest officials.