Despite concern over the conservation status of many Mongolian salmonids and the
importance of their ecological role in Mongolia’s aquatic ecosystems, little is known
about their basic biology. Hovsgol grayling (Thymallus nigrescens) is endemic to Lake
Hovsgol, Mongolia and listed as endangered on the Mongolian Red List. Baikal grayling
(T. baicalensis) and lenok (Brachymystax lenok) are found in lakes and rivers throughout
the Selenge drainage. A detailed study of the age and growth of these three salmonids
was conducted based on 1,682 samples collected from July 2006 to July 2013 in Lake
Hovsgol, its outlet the Eg River, and one of the Eg’s largest tributaries, the Uur River.
Our results suggest that Hovsgol grayling in particular can reach a much older maximum
age (17 years in our samples) than previously believed based on aging from
scales. Female Hovsgol grayling were heavier at a given length than their male counterparts.
Lenok had a greater average length-at-
age
in Lake Hovsgol compared to the
rivers and greater weight-at-
length
in the warmer Uur River than in the Eg; female
lenok from the rivers had a greater average length-at-
age
than their male counterparts.
This study provides critical new information for the management and conservation
of these threatened salmonid species in Mongolia.
