Feeding ecology of lenok (Brachymystax lenok), Hovsgol grayling (Thymallus nigrescens) and Baikal grayling (Thymallus baicalensis) from the Eg-Uur Watershed, Mongolia

Abstract

The Eg-Uur Watershed of Northern Mongolia is home to several unique salmonid species which are believed to be declining due to the rapid industrial development currently taking place in Asia. We used a combination of stomach contents and stable isotopes of carbon and nitrogen to examine the degree of dietary niche overlap of lenok, Baikal grayling and Hovsgol grayling in lake and stream habitats of the Eg-Uur Watershed. Lenok and grayling exhibited vertical partitioning of prey resources despite differences in prey availability between lake and stream habitats. Within stream habitats, prey availability was positively related to diet overlap, suggesting that competition is involved in the resource partitioning we observed. Our analysis also revealed the presence of specialist planktivores within the Hovsgol grayling population. The results from this study provide a baseline description of prey utilization and partitioning between lenok and grayling (Thymallus spp.).