Before the lowering of water level of the lake Sevan the annual fish hunting consisted almost equally of trout and carp (accordingly 50 % and 40 %). In this time period the portion of whitefish in annual hunt portion was 0.29%. In the initial period of water level lowering of the lake (1939-1962), because of the artificial increase of the watercourse of the river Hrazdan, the morphometric and hydrodynamic indices, temperature regime of the lake Sevan were changed.
Since the beginning of 1940s the number of trout began to reduce, but in the mid-1960s due to the drying of spawning places in the lake the regeneration conditions of trout were deteriorated sharply. Some appropriate conditions were created for regeneration of whitefish in this time period and since of 1960 the stocks of whitefish are growing making in 1965 up 40% of annual fish hunting. The portion of trout reduces up to 27.5%, the portion of yellowfish reduces up to 32%. Sevan yellowfish is spawning in the lake as well as in in the rivers flowing into the lake, because of reduction of spawning places in the lake basin the conditions for breeding of yellowfish are violated and in result of that the resources are reduced.
In the lake trout stocks continue to decline due to the growth of peat, in result of which trout extraction has been banned since 1976, in 1978 it was included in the USSR Red Book, in 1987 the trout together with Gokcha barbel (Barbus goktschaicus) were registerted in the Red Book of Armenia. The number of whitefish in this time continues to rise and in 1970s its industrial biomass reaches 12000-13000 tons. In the end of 1980s and in the beginning of 1990s the stocks of whitefish reaches to the maximum quantity making 16000-18000 tons.
Since the early 1980 s the number of carp in the lake began to grow rapidly.
Currently only whitefish and carp are extracted from the lake. In addition, whitefish makes up more than 80% of total hunting. From 4 subspecies of the trout in the lake Sevan there are only egg laying forms in the river: Salmo ischchan gegarkuni and Salmo ischchan aestivalis. The population of Salmo ischchan aestivalis is currently on the verge of extinction