Bioenergetics Models for Mongolian Salmonids: Lenok and Arctic Grayling Derived from Streamside Metabolism Measurements

The Eg-Uur River ecosystem in northcentral Mongolia provides an opportunity to study salmonid species in a system relatively undisturbed by human influences other than climate change. These species are currently imperiled in Mongolian waters, with Arctic Grayling (Thymallus arcticus) listed as near-threatened, Lenok (Brachymystax lenok) listed as vulnerable, and Taimen (Hucho taimen) listed as endangered on the Mongolian red list (Ocock et al. 2011).  Air temperature records demonstrate that in the last 40 years Northern Mongolia’s rate of warming is 3 times the northern hemisphere average.  Despite alarming trends in air temperatures, little is known of the thermal ecology of these species. Due to the threat of climate change to these species the objective of our study was to quantify metabolic costs for these species from streamside routine metabolic measures and derive bioenergetics models that can be used to assess potential climate change responses.  Streamside measurements of metabolism were remarkably consistent with expectations from measures of other salmonids gathered under more closely controlled laboratory conditions.  Metabolism increased exponentially with temperature for both species.  The resulting preliminary bioenergetics models suggest these species are already experiencing temperatures near their upper levels for growth during summer and conditions are expected to deteriorate with warming.