author(s)
Mohd Danish, Pooja Badoni, Karma Rinya, Supravat Maity, Anjan Chowdhury and Tushar Subhra Khanra

abstract
Fish as a group, apart from its nutritional value from a biodiversity point of view, has the highest species diversity among all vertebrate taxa. Fishes exhibit enormous diversity in size, shape, biology and in the habitats they occupy. Fishes form a highly successful group of animals comprising more than 30,700 species inhabiting all seas, rivers, lakes, canals, dams, brackish water, estuaries and all places wherever is water. Major carp species contribute very significantly in total fish production of our country. Labeo rohita and and Cyprinus carpio var. communis are one of the most important culture species in aquaculture system and facing the problem of inbreeding in captive stocks and problem of overexploitation in wild stocks resulting reduction in level of heterozygosity and genetic diversity thereby it is important to analyze genetic structure of these species in order to devise and aid for their stock management and conservation. Unintentional inbreeding is a common default practice in hatcheries. A molecular marker is a site of heterozygosity for some type of silent DNA variation not associated with any measurable phenotypic variation. Such a “DNA locus,” when heterozygous, can be used in mapping analysis just as a conventional heterozygous allele pair can be used. Genetic variation in a species enhances the capability of organism to adapt to changing environment and is necessary for survival of the species. Various molecular provide different scientific observations which have importance in aquaculture practice recently such as: 1) Species Identification 2) Genetic variation and population structure study in natural populations 3) Comparison between wild and hatchery populations 4) Assessment of demographic bottleneck in natural population 5) Propagation assisted rehabilitation programmes.