Abstract
In South and South East Asia three genera of fish species i.e. Tor, Neolissochilus and Naziritor are commonly known as Mahseer with at least 47 species. Among these 23 belongs to genus Tor, 22 to Neolissochilus and one to Naziritor i.e. Naziritor zhobensis. Recently another species added to genus Naziritor is Naziritor chelynoides in India. Among Tor species Tor putitora (Hamilton) is the most widely distributed Mahseer in Pakistan and other countries of the Indian subcontinent. However, based alone on morphological characters some authors identify the Pakistani counterparts as Tor macrolepis (Heckel), (a species presumed to be found exclusively in the Indus River system) distinct from Tor putitora (a species found in Ganga Brahmaputra River system). In order to resolve this taxonomic ambiguity, present study carried out meristic and morphometric measurements of Mahseer collected from a total of 11 water bodies of Pakistan. Ratios between the morphometric characters were calculated and statistically analyzed using t-test and correlation coefficient. Two species identified as Tor putitora and Naziritor zhobensis were the sole Mahseer inhabitants of Indus system in Pakistan. Tor putitora occurred at all surveyed sites while Nazirtor zhobensis had a distribution range from river Zhob to tributaries of river Gomal the right bank tributaries of River Indus. The study corroborates that there are no unequivocal morphological synapomorphies in any existing populations of both species. The study further demonstrates that head length, a character frequently used in Mahseer taxonomy, is not a good measure for species identification. Finally the present study establishes that Naziritor zhobensis still exists in the water bodies of Pakistan and that golden Mahseer occurring in Indus riverine system of Pakistan is Tor putitora.
Highlights
The fish belonging to three genera i.e. Tor, Neolissochilus and Naziritor are generally known as Mahseer, a game and food fish naturally found in Nepal, Pakistan, India, Sri Lanka, Bangladesh, Myanmar, China, Thailand, Laos, Cambodia, Vietnam, Indonesia and Malaysia (Shrestha, 1990)
Ratios of various morphometric measurements in percentage were calculated in relation to Total length (TL), Standard length (SL) and Head length (HL) (Table 3)
The pre dorsal length was more than post dorsal length, HL was more than Body depth (BD) and HH and the Eye diameter (ED) was more than both eye/interorbital distance (BED)
Summary
The fish belonging to three genera i.e. Tor, Neolissochilus and Naziritor are generally known as Mahseer, a game and food fish naturally found in Nepal, Pakistan, India, Sri Lanka, Bangladesh, Myanmar, China, Thailand, Laos, Cambodia, Vietnam, Indonesia and Malaysia (Shrestha, 1990). Naziritor zhobensis was first time reported by Mirza (1967) as Tor zhobensis from the Zhob River and is commonly known as the Zhobi Mahseer. According to Sati et al (2013) there are 47 species, commonly referred to as Mahseer, i.e. 23 belongs to genus Tor, 22 to the genus Neolissochilus and one only to genus Naziritor i.e. Naziritor zhobensis but Khare et al (2014) added another species to genus Naziritor i.e. Naziritor chelynoides. According to Desai (2003) seven Mahseer species are known from the Indian subcontinent to which Pakistan belong. These are Tor putitora (Hamilton, 1822), T. tor (Hamilton, 1822), T. mosal (Hamilton, 1822), T. mussullah (Sykes, 1839), T. khudree (Sykes, 1839), T. kulkarnii (Menon, 1992) and T. progeneius (McClelland, 1839). Most of the species belonging to genus Tor are included in threatened list of IUCN (Lakra et al, 2010)
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