The Feeding Behaviour of Fish from the Upper Lake Baikal Watershed of the Eroo River in Mongolia

Abstract

The upper Selenge watershed in Mongolia is home to some of the world’s unique fish species. In this study we determined the feeding behaviour of selected fish species collected from the main stream of the Eroo River and two of its upstream tributaries, the Sharlan and Bar Chuluut rivers. Using stable isotope (carbon and nitrogen) measurements combined with qualitative and literature information, we determined that taimen ( Hucho taimen ) and pike ( Esox luceus ) were the top predators in the Eroo River. They received a substantial amount of their energy from other fish species as well as terrestrial derived sources. Percent presence of biota in lenok ( Brachymystax lenok ) stomachs demonstrated they eat zoobenthos, invertebrates, fish, and terrestrial rodents. Siberian dace ( Leuciscus baicalensis) , a small forage fish collected from the Sharlan and Bar Chuluut rivers demonstrate these fish eat periphyton, zoobenthos and terrestrial invertebrates. In the Bar Chuluut tributary, lenok eat a combination of foods including zoobenthos and other fish species, while arctic grayling ( Thymallus arcticus ) fed primarily on zoobenthos. Percent frequency analysis showed the two game fish species collected from the Bar Chuluut tributary fed primarily on zoobenthos (85 % for lenok and 80 % for grayling), with 28 families and 10 orders represented in their stomachs. Interviews with families suggested local people fish for a variety of species and that there has been a decline in the catch of taimen and sturgeon ( Acipenser baeri baicalensis ) over time. Since fishing was poor below highly disturbed areas (e.g. mine sites), local people fished above mine locations or in areas least impacted by these anthropogenic impacts.

Keywords

• gold mining
• Lake Baikal
• Mongolia
• Selenge River