The fish surveys were conducted to estimate the fish distribution, densities and spawning condition in the streams of the Borsog, Dalbay, Sevsuul, Noyon, Shagnuul and Turag valleys along the eastern shore of Lake Hovsgol. During the research period we surveyed three sites in each of the six survey streams.
For each species, we have recorded the following information:
- Total, Fork and Standard Length (morphological measurements of the fish were taken to nearest mm)
- Weight (record weight to nearest gram 0.1g)
- Sex (examine gonads visually and determine stage of maturity and determine whether the gonads are in early development, late development, ripe and running, or spent)
- Collect additional biological tissues (scales and otholiths)
- Growth rate of the fish
For each sample we recorded the following information:
- Gear type used for fishing (electrofishing, nets, gill net)
- Hydrological and water chemistry conditions and shallow water habitat characteristics
- Complete data sheet with species, date of sampling, fish condition, location and any other relevant conditions.
Fish Distribution and Species Composition
The Ichthyofauna in this area is very poor in number of species. A total of 10 species of 8 families of fish have been recorded in Lake Hovsgol and its tributaries. They are Brachymystax lenok (Asian Trout), Thymallus arcticus arcticus (Arctic Grayling), Thymallus arcticus nigrescens (Hovsgol Grayling), Rutilus rutilus (Roach), Phoxinus phoxinus (Common Minnow), Perca fluviatilis (Eurasian Perch), Cobitus melanoleuca (Spiny Loach), Barbatula toni (Stone Loach). The Baikal omul, Coregonus autumnalis migratorius, was introduced to the lake but is not well established.
Upper sites of the streams have mountainous character and river channel has not developed and stream velocity ranged from 1.01-1.5 m/s and the middle sites of each streams have well created water channel and stream velocity ranged from 0.3-0.6 m/s and lower sites of the streams have a steppe character and stream velocity ranged from 0.1–0.4 m/s. The spawning ground length area is different in each of the selected survey streams. The upper site of the Turag and Dalbay have an average depth of 20-50 cm, and are characterized by medium sized gravel bottoms, and the current is suitable for the spawning of Lenok and grayling. Lenok and Arctic grayling generally start spawning from mid-May to early June in cold water (from 6-10°C)
Relative abundance of the assemblage was determined as number of individuals per unit effort in the catch. According to spawning results, Borsog River and Dalbay River are Roach and Perch types, the Noyon and Sevsuul are lenok and minnow types, and the Sevsuul River and the Turag River have grayling and spiny loach type streams.
The Hovsgol National Park covering 838.070 hectares and adopted at the state protected area in 1995. No fishing is allowed in the following special protected areas-rivers on the study streams: Borsog, Dalbay, Sevsuul and Noyon. Shagnuul and the Turag are special fishing area and Turag is a very good place for sport fishing. The Asian trout (Brachymystax lenok) and two subspecies of grayling are of fairly great and increasing sport fishing interest in fishery. During the spawning time when fish migrated to the rivers, local people caught a large number of fish. Poaching has the most effect on the mortality during the fish spawning period. We saw during the spawning period for one day; four people who caught more than 6240 grayling. The number of foreign tourists who are interested to travel to Mongolia and the local tourist who catch fish from the lake increases every year.
With the increase in the number of foreign tourists the local residents are very interested in selling smoked fish to the tourist camps, as well as fresh fish. There is only one ranger for the three northern study valleys. There are limits and control on the quantity of fish removed. In addition, there is almost no fee applicable to the fishers, although allowed by Hunting Law of Mongolia.
Our main interest has concerned the “lake-river form” of the populations inhabiting Lake Hovsgol. They perform massive spawning migrations into the tributaries of the lake system, mainly into the eastern shore rivers. Some survey stream substrates are poor for spawning or the stream may go dry. From the survey streams, the upper sites of Turag and Dalbay Rivers have large amounts of medium-sized cobble (100-128 mm). This substratum is suitable for Salmonid spawning. The mid-site of the Dalbay and Turag Rivers have a relatively high abundance of fry of Asian trout, grayling and minnow, the water temperature and feeding behaviors are suitable for the growth of fry.
Regression analysis revealed a significant relationship (p<0.0001, r2=0.45) between fish abundance and water temperature, the water temperature appears to play a minor ecological role in the egg development. The biomass in pools and raceways at the sites found mean depth explained 80% of the variation in biomass. The logarithm of abundance (biomass) was significantly correlated with depth (p<0.0001, r2=0.77).
The fish distribution pattern in habitats in lower sites was not similar. The highest density and biomass was observed in lower sites of the Dalbay River and the lowest was in the Shagnuul River. The estimated of biomass at the lower sites are at the high and upper sites are at the low and range reported for fish interactions and hydrological condition and peculiarities of habitat, which suitable for spawning ground and riparian vegetation and grazing impact. At 18 sites to range from 0.019-0.137 kg/m2.
In Lake Hövsgöl, Asian Trout generally reach maturity in 5 years. The young of the maturity year-class dominated during the spawning. The maturity females and males sex ratio was constant. Eggs from average weighted (1136 g) Asian Trout herring are 3.2 and 4 g/100 eggs. Number of eggs of Asian Trout in a Turag River and in a Sevsuul River tended to be higher than at the other sites. The Turag is highly productive river, but personal observation and interviews with local anglers get that during the spawning time in this river very high poaching. With shallow water anglers very often caught fish and often focusing on larger species. It’s negatively influenced for reproductive of the young of the young species.