The World’s Largest Trout: A Mongolian Expedition

David Gilroy
Taos High School
Café Scientifique New Mexico, Taos


David Gilroy took us on a journey to the back country of Mongolia to explore the unique habitat of the world’s largest trout — which grows up to six feet long! David wove a compelling story of the science of fish population studies, foreign culture, mis-haps, and adventure.


More about the trout

The taxmen, also known as siberian taimen and world’s largest trout, is a species of fish in the salmon family.In Mongolia, the taimen is found in both the Arctic and Pacific drainages, specifically the Yenisei/Selenga, the Lena, and the Amur River Basins. The taimen lives in flowing water and is only occasionally found in lakes, usually near the mouth of a tributary. The taimen is not anadromous, but does show increased movement rates during the spawning season.

Coloration varies geographically, but is generally olive green on the head blending to reddish brown in the tail. Adipose, anal, and caudal fins are often dark red. The belly ranges from nearly white to dark gray. The taimen is one of the largest salmonids in the world. Most mature fish caught weigh from 33 to 66 lbs. The average length is from 28 to 47 in. The maximum size is not assured, but supposedly a fish caught in the Kotui River in Russia in 1943 with a length of 83 in and a weight of 231 lb is the largest size recorded. The maximum length is about 59 to 71 in. The IGFA world record is 92.5 lb or 41.95 kg with a length of 156 cm. It can reach at least 55 years of age.

Hands on Activity

Students were able to explore the procedure of determining species’ numbers by population sampling. Attendees were divided into two groups: the field scientists and “the fish.” With fishing rods (made of sticks, string and baited with marshmallows) our scientists lured in their “fish”, determined their species, recorded their size, sex, etc. and released them back into the wild. Using mathematical formulas they calculated the fish species’ population.