Date of this Version
Erforschung biologischer Ressourcen der Mongolei (2012) band 12: 231-243.
In connection with the planned establishment of a coregonid fishery and the construction of a specialized hatchery in the area of Western Mongolia a study was undertaken with the aim of studying some parts of the reproductive biology of population of Coregonus peled inhabiting the lake Ulaagchnii Khar (Zavhan aimag). This species was introduced into this Mongolian lake, originally lacking any fish stock, in the period from 1980–1982. 11,230 fish were collected and examined during the periods from 1993–1999 and 2005–2011 and consisted partly of the fish originating from imported and introduced larvae and partly of the individuals belonging about 25th generation, already born in the lake. Most of the parameters studied, such as absolute size, weight, population dynamics, reproduction biology, food analyses, and body fat percentage were taken during observations and collections made during the vegetation period (November – December and first half of January), when the minimum daily waters temperature drops to 4°C or less. The sex ratio is fairly balanced when all material from all collection events is considered. During the period of peak-spawning, females predominate. The average individual standard length of spawners was 400 mm in males and 420 mm in females; the average weight 700 g in males and 900 g in females. Nevertheless, all parameters studied tended to decrease slightly through time, which is evidently a result of the gradually increasing numerical density of the fish and of the corresponding decrease in quantity of food available in the lake. In Khuisiin Naiman Nuur (Aimag Övörchangaj) fish became sexually mature at the age of 2+, and exceptionally, at the age of 1+, at the minimum total length 323 mm and minimum weight 295 g, respectively. The gonadosomatic index of mature females ranged from 9.0 to 25.0 %, and the mean absolute fecundity averaged 58,060 eggs.