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Rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta fario) are popular salmonid species that are reared for sport and recreational activities worldwide. In India, they were introduced and successfully established in the late 19th and early 20th centuries by the European settlers. However, until now, no studies have analysed the genetic integrity of wild trout populations in India. Therefore, this study aimed to analyse the genetic integrity of the wild rainbow trout populations from south India, one wild rainbow trout population from north India, and one wild brown trout population from north India. Genetic diversity studies revealed low genetic diversity in all the population with genetic bottlenecks in two trout populations from south India and disruption of alleles in the populations from north India. The results showed that the south Indian trout populations are in a comparatively poor condition than the north Indian trout populations, and stocking efforts have recently been carried out to enhance the genetic diversity of south Indian trout populations. [ABSTRACT FROM AUTHOR]

Rainbow trout, Oncorhynchus mykiss (Walbaum, 1792), is a popular cold-water fish widely distributed and farmed globally. In the nineteenth century, rainbow trout were introduced into India, and since then, it has gradually spread and established itself as one of the most prevalent non-native fish. In Southern India, rainbow trout were introduced from New Zealand in 1909 in the Ooty region of the Western Ghats, followed by introductions in other coldwater regions in the Peninsular uplands such as Munnar and Kodaikanal. Continuous introductions were done from various geographical locations at different periods to increase O. mykiss stocks in the Peninsular upland regions. Despite being regularly introduced in the streams of Munnar, Ooty, and Kodaikanal of Southern India, they still have not become self-sustaining, and genetic diversity has been suggested as a potential underlying factor. Therefore, this study aimed to resolve these questions and explore the structure and origin of Southern Indian stocks by conducting a population genetic study. The Y-linked marker of the trout stocks sampled from Munnar, Ooty, and Kodaikanal was compared with that of the native populations from North America. The results showed less proportion of inter-population genetic variation, suggesting that Southern Indian stocks were derived from multiple origins of population, with a great majority of parental populations belonging to the coastal rainbow trout from North America. This study revealed no considerable genetic differences among the Southern Indian stocks and reported the major ecotype as the Steelhead trout, Oncorhynchus mykiss irideus (Gibbons, 1955). [ABSTRACT FROM AUTHOR]