Mahseer is a group of fish species that are well known as food and game fishes. The taxonomy of the mahseer species is confusing owing to the morphological variations and habitat adaptation. Detailed karyomorphological investigations have been carried out in seven species of mahseer, using karyotyping, Ag-NOR and fluorescent staining techniques. The basic diploid chromosome number (2n), in all mahseer species, was observed to be 100; however, the karyotype formula varied among the species, which were recorded as: 20m + 14sm + 22st + 44t (fundamental arm number, FN = 134) in Tor khudree; 22m + 24sm + 24st + 30t (FN = 146) in Tor mussullah; 12m + 22sm + 14st + 52t (FN = 134) in Tor putitora; 20m + 24sm + 24st + 32t (FN = 144) in Tor tor; 20m + 30sm + 24st + 26t (FN = 150) in Tor chelynoides; 20m + 20sm + 20st + 40t (FN = 140) in Tor progeneius; and 20m + 18sm + 14st + 48t (FN = 138) in Neolissochilus hexagonolepis. Silver staining of the chromosomes revealed the presence of multiple nucleolar organizer regions (NOR) in these mahseer species. The highest number of NORs was observed in T. tor (four pairs of chromosomes), whereas the other six species possessed Ag-NOR signals on only two pairs of chromosomes. Although chromomycin A(3) (CMA(3)) staining induced bright fluorescence signals on same Ag-NORs sites, with CMA(3), one additional signal was observed on the p arm of subtelocentric chromosomes in T. tor, T. chelynoides, T. progeneius and N. hexagonolepis, which may indicate the presence of inactive NOR in these species. The information on cytogenetic profile of these mahseer species is discussed in the light of cytotaxonomic implications and understanding the karyoevolution of these fish species.

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The recent climate change and anthropogenic activity affects the agricultural land/soil as well as aquaculture sector via salinization of the aquatic zone. The present study aimed to investigate the effect of salinity on genetically improved farmed rohu, Labeo rohita popularly known as Jayanti and evaluation of its physiological response towards combating salinity stress. Genetically improved rohu (Jayanti) fingerlings were reared in laboratory condition at different salinities 2, 4, 6, 8 and 10 ppt to assess the effect of salinity on survival for the first time in India. The study revealed that the Jayanti rohu fingerlings could tolerate salinity upto 8 ppt range. The survival rate of the fingerlings varied from 100%, 95%, 80% and 75% at 2, 4, 6 and 8 ppt salinities, respectively and 100% mortality occurred at 10 ppt. The survival rate was significantly higher in lower salinities than other acclimation salinities. The hematological parameters analysis depicted that blood parameters were affected by increase in salinity beyond 6 ppt. The histological analysis reported mild lesions on gills of fishes exposed to higher salinities at 8 ppt. The present study revealed that exposure to salinity moderately affects the survival and physiological response of genetically improved rohu and thus the potential of the improved rohu “Jayanti” to tolerate salinity levels upto 8 ppt. These results suggest that there is great prospective for culturing selectively bred rohu (Jayanti) species in low saline areas or salt affected areas with good survivability and open new avenues for further research and development.