Taimen are the world’s largest freshwater salmonid and their historic range included Central Asia, Mongolia, China, Siberia, the Russian Far East, Japan and the Korean Peninsula. Records suggest that 6.5-feet long / 200-pound (2m/90kg) behemoths once prowled these rivers.
This unique fish is incredibly slow-growing, long-lived (up to 40 years), and late to reach sexual maturity at between five and seven years). Taimen are apex predators, existing on a scale different from nearly all other freshwater species. Most scientists estimate that the healthiest Mongolian rivers contain no more than twenty adult taimen per kilometer. If one considers that these same stretches of river likely hold hundreds or thousands of lenok and grayling, taimen are found at a very low population density. Today, giant trophy taimen over fifty-inches (1.25m) are even more widely dispersed. Sadly, only a handful of these great fish inhabit even the best of taimen watersheds.
Taimen populations in Mongolia are threatened by poaching, habitat loss due to mining, overgrazing, other development activities, as well as unsustainable recreational fishing practices. In 2012 the IUCN added taimen to their Red List of Threatened Species, finding:
In Mongolia, H. taimen distribution has decreased by about 60% since 1985 suggesting a population decrease of at least 50% (Ocock et al. 2006). For this assessment, we estimate range loss (estimated as extent of occurrence, or EOO, between 1980 and 2008) to be 19.1%. There are continuing declines in the quality of habitat (due to mining) and in the number of mature individuals. It is suspected that the population will decrease by over 60% in the next 20 years as demand increases from China and Russia and from non-catch and release angling (Ocock et al. 2006). In Mongolia, fish have disappeared from rivers near town centres and downstream of mining areas. Stable populations still occur in more remote areas but these populations are vulnerable as mining, overgrazing, and fishing become more common in Mongolia.
Their complete report may be found at www.iucnredlist.org/details/188631/0