Introduction
Conservation of genetic diversity is critical for the continual survival
of the fisheries industry and plays a pivotal role in the socio-economic
development of our nation. Owing to the challenges associated with the
ever-increasing demands for resources and the need to conserve fresh
water bodies, the onus for ecological conservation now lies with local
and regional biodiversity regulators and policy-makers. This demands a
decisive shift from piecemeal steps to a comprehensive and practical
multidisciplinary approach for conservation gambits (Adrian et
al ., 2019). The fisheries segment provides employment to 14 million
individuals in India, and a lack of species conservation could have
serious ramifications on employment in the sector. Conservation plans to
perk up the declining wild fish populations have been delayed by an
unstable taxonomy.
Mahseer is a popular game and food fish of India. It provides
unparalleled recreation to anglers from all over the world as a sport
fish superior to the salmon. However, anthropogenic activities such as
dam-building and over-fishing have adversely affected the Mahseerpopulation across the country. Once an abundant species, theMahseer population has been decreasing in natural waters and the
different Mahseer species are now either categorized as
“threatened” or “endangered”. Moreover, T tor has been
recently classified as a data deficient species (Rayamajhi et
al. 2018);
there is, therefore, an urgent need to validate the conspecificity of
the species from the river Mahananda (northern Bengal) with records
of T. tor from other parts of India. However, the presence of
only a few haplotypes of Mahseer species (Tor tor ),
indiscernible morphological features, and paucity of research on
accurate classification (Jayaram, 1999) have led to confusion in
accurate taxonomic classification of this fish.
The advent of molecular biology and DNA markers has helped the progress
of pisciculture by enabling the study of genetic variability, breeding
patterns, institution of parentage identifying strain and species and
high-resolution genetic linkage maps.
As genetic markers are important tools for the study of fish species and
population characterization, the development of molecular methods has
permitted genomic analysis and made the analysis of existing variations
possible. Similarly, gene frequencies of mitochondrial genes are also
indicative of phylogeny and close associations. Cytochrome oxidase
I (COI) , a mitochondrial gene, is a popular target for species
identification and barcoding; it has been reported that approximately
98% of reported marine fish species can be identified by COIbarcoding. This approach has been employed to catalogue and record fish
in many geographic regions (Asgharian et al. , 2011; Aquilinoet al. , 2011 and Cawthorn et al ., 2011). However, there is
a dearth of genetic studies conducted on Mahseer species in
India. Older studies have mainly explored taxonomy based only on
morphological characteristics and therefore, there is a need to perform
molecular studies [such as those by Nguyen et al. (2008)] to
aid in the conservation of this endangered species. There is paucity of
studies on Mahseer genetic structure reported across the Indian
waters (Sati et al ., 2013) and in Rajasthan state. An examination
of the mitochondrial genetic information of nine Mahseer species
belonging to the Tor, Neolissochilus, and Naziritor genera
was performed by Khare et al. in 2014. Their study highlighted
the need for integrating molecular and morphological data to accomplish
taxonomic revision of the Tor and Naziritor genera.
The mitochondrial genome has been effectively used for phylogenetic
analysis and to solve taxonomic ambiguity in Mahseer species
(Pavan-Kumar et al ., 2016). Therefore, we undertook this study to
perform phylogenetic analysis on Mahseer species indigenous to
southern Rajasthan using mitochondrial DNA sequences.
In the present study, we have analysed haplotype diversity ofMahseer (Tor sp.) from southern Rajasthan using theCOI gene frequencies. Accurate taxonomic identification using
molecular markers is an indispensable step towards the protection of
this endangered fish.