The Tuul River is no longer a home for animal life due to water contamination caused by human related activities. Numerous dead fish have been found on the river bed for a one kilometer area near Marshall Bridge.

A survey to determine the cause of fish loss was made by a specialist scientist in water resources and usage from the Institute of Geology, B.Mendsaikhan and veterinarians bacteriology of the State Central Veterinary Laboratory, N. Munkhgerel and B.Batzorig. A professor from the Department of Zoology and Ecology of the National University of Mongolia, Kh.Munkhbayar and P.Erdenetushig conducted an inspection to determine the reason for the death of frogs in the river.

The survey said that a 1.8-2.5 meter deep and 25-30 meter wide pool caused the death of numerous fish and frogs. The researchers said that a stagnant habitat instead of flowing water created at the bottom of the pool was the reason of the fish deaths.

The habitat of the Tuul River is so contaminated for life forms that even hydrobiots are no longer able to survive.

According to the survey fish and frogs that entered the pool last autumn became stuck there and died due to lack of oxygen.

The slowing of the flow of the Tuul River occurred in 2012, depth of ice was lowered to 10-23 cm less than the annual average. This water level lowering is explained by gravel mining companies along the river.

Such factors played a big role in the destruction of the habitat of life forms in the Tuul River.