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Impact of Livestock Grazing and Climate Change on Biodiversity of the Eastern Shore Tributaries

Amar Dulmaa, Bud Mendsaikhan, Enkhtaivan Sanaa and Tsegmid Bokhchuluun

The main objective of this study is to identify the impacts of land use and climate change in the tributary valleys of Lake Hövsgöl on the species composition and biological diversity of aquatic organisms such as diatoms, aquatic invertebrates and fishes.

Diatom study

Diatoms are important representatives of primary producers in aquatic habitats. Accordingly, the diatom communities encountered are the result of environmental conditions so diatom communities reflect the human and livestock impacts. In June to August of 2002-2004, 325 diatom samples were collected from the benthic habitats: epilithon, epipelon, epipsammon and epiphyton and analyzed for diatom species richness dominance, and species relative abundance. 424 diatom taxa from 65 genera were identified from the periphyton. Whereas diatom species are few, relative abundance is higher in Borsog and Dalbay Rivers. In contrast, diatom species is higher, relative abundance is lower in Turag, Shagnuul, and NoyonRivers. Genera with the greatest taxonomic richness are Cymbella (10 taxa), Eunotia (10 taxa), Fragilaria (18 taxa), Gomphonema (20 taxa), Navicula (38 taxa), Nitzschia (31 taxa). The Achnanthidium minutissimum may prove useful as an indicator of human and livestock impacts with a significantly higher abundance in Turag. Average relative abundance of Synedra ulna, fresh water indicator, in different in Borsog and Dalbay rivers than other rivers. Canonical correspondence analysis (CCA) was used to explore the relationship between diatom assemblages and measured environmental variables. A result of community analysis was very different stream assemblages based on the similarity in species composition between stream assemblages. The highest percentage of motile diatoms was found in Noyon and Shagnuul River. We can estimate riparian soil erosion by motile diatoms percentage. If percentage of motile diatoms more, we can say more riparian soil erosion is there.

In result of the study, the distribution of 42 species in 15 genera and a genus Diatomella balfourina were added to the Mongolian diatom flora. Also an unknown species included in genus Gomphonema was identified. Global climate warming, pasture use and overgrazing are influenced on biodiversity loss and diatom species composition. In current years, in the some rivers of eastern shore LakeTurag River have already influenced by human and livestock impacts. Hovsgol, moderate disturbance is observed due to high livestock-grazing level. Further, indicator diatom species of polluted water are spreading in addition on fresh water, sensitive species. Though diatom species diversity is appeared higher, if these ecological conditions continue for long term, it might be possible that only few polluted water indicator species leave by their toleration, diatom diversity and bioproduction decrease and diversity of feeding insects on diatom also decrease. All statistical results are view Borsog and Dalbay rivers are freshwater,

The study has been continuing and it seems hopeful to record many new distributions, new species and prepare diatom local training set.

Fish study

A total of 10 species of freshwater fish belonging to 9 genera have been recorded in the Lake Hövsgöl and its tributaries. In the tributaries of the lake Hövsgöl fishes, which are typical to the Siberian water bodies, predominated, including lenok (Brachymystax lenok), Roach (Rutilus rutilus), Perch (Perca fluviatilis) and Spiny Loach (Cobitis melanoleuca). Only the Hövsgöl grayling (Thymallus nigrescens) is endemic at lake Hövsgöl and the Arctic Cisco or Baikal Omul (Coregonus autumnalis migratorius) was introduced in 1956 (Dashdorj. A).

The objectives of fish study are to define the impacts of nomadic pasture activities use and climate change on the distribution of fish species, spawning success, survival of young, changes in fish diets and population differences. Six valleys were established to study the spawning patterns, ecological condition in the spawning grounds, and spawning behavior and their food diet. Fish studies were done longitudinally along the streams. Fish were collected between 2002 and 2005 at 18 sites in streams.

The spawning of Salmonids at the sites was largely determined by temperature, oxygen and hydrological condition and gravel bottom substrates. The lenok, the Hövsgöl grayling, the roach, the perch, the minnow (Phoxinus phoxinus), stone loach (Barbatula toni) and spiny loach are spring and summer spawners fish. Fish spawning habitat occurs in places with the good hydrological, water chemical and biological conditions. Annual air temperature in this of the region has warmed by about 1.5°C. This factor was influence on spawning process of Salmonids species. The upper sites of some rivers were dryed during the spawning period. This drying does appear to have affected fish spawning and migration. Spawning of Salmonids began in Sevsuul, Turag, Noyon and Dalbay Rivers end May an average temperature 6.3-7.8°C, and in Shagnuul and Borsog Rivers spawning began in mid June. For the spawning substrate and habitat the tributary of the Borsog and Dalbay are roach, perch and burbot (Lota lota) types, the Noyon and Turag are lenok and grayling types, Sevsuul and Shagnuul are spiny loach types. Lower river levels tended to reduce the effects of temperature increases were negatively affected for Salmonids.

The percentage recruit spawners in the river sites were different during the reproductive period. The low recruitments in the Shagnuul River determined that drains the valley with the most intensive grazing were attributed to high concentration of sedimentation and salinity, hardness and lower river level, based on temperature and low concentration of dissolved oxygen. The spawning season in May-June the lenok were mainly of ages 6-9, the Hövsgöl grayling was of ages 3-6, the perch and roach were older in age >9+. The percentage recruit spawners in the river sites were different during the reproductive period. The lenok population had slow growth rates, similar for six populations. Almost fish of this lake are very limited by spawning habitat and hydro logically unstable streams play an important part in regulating of fish migration.

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