Recent data on biology and ecology of peled Coregonus peled which was introducing into Ulaagchny Khar Lake in Western Mongolia in early 80^th are presented. Based on the data 2011–2014 the population consists up to 16 age groups. Some of biological traits of peled were decreased during the naturalization period due to feed resources depletion and diet shifting. Compared the first decade of acclimatization in 2011–2014 size and weight were decreased in 3–6 times in different age groups and age of maturity was slided from age 1+ to 3+. The notable interannual differences of absolute and relative fecundity are established. Since second year of life peled diet shifts from zooplankton to benthic invertebrates. Adult fish have a diet largely dominated  by Gammarus lacustris troughout the year.