MICROSATELLITE MARKERS BASED GENETIC STRUCTURE OF ROHU (Labeo rohita) IN SELECTED RIVERINE POPULATIONS OF PUNJAB, PAKISTAN

In an ever-changing environment, genetic diversity assures the species fitness by providing potential to cope effectively with environmental challenges and natural selection pressure. Biological diversity of any species is dependent on the phenotypic plasticity and adaptability of its populations to the natural environment and anthropogenic interruptions. Environmental hazards such as floods, climatic change, and human interventions including hydrological alterations, pollution, introduction of exotic species, and overfishing are major factors effecting the survival of fish species during last several decades (Vandewoestijne et al., 2008). The major carp L. rohita, locally known as ‘Rohu’ is the member of family Cyprinidae and belongs to the top ten most commercially valuable species of aquaculture in the world. It is widely distributed in riverine systems of Pakistan (Rafique and Khan, 2012). Like many other aquaculture species in Pakistan, Rohu (L. rohita) aquaculture is facing issues with regard to seed quality including poor genetic management of brood stock. A very little genetic information is available about this species in Pakistan. Currently, the natural seed production of L. rohita has been reduced with contribution level less than one percent. The L. rohita population in riverine system of Punjab has been threatened by a wide range of factors but genetic diversity of this species has declined mainly due to anthropogenic interruptions that include the species introductions, impoundment of rivers, habitat degradation, water quality deterioration, and overexploitation. Anthropogenic intervention is the most important factor contributing towards loss of genetic resources of fish populations in the wild (Frankham, 2003). The hydrological alterations and increased human intervention during past years has resulted in loss of spawning, breeding and nursing grounds in natural water bodies. Dams construction interrupt the migration of many fish species and thus interfere with their life cycles (Agosthinho et al., 2008). The pollution adds to the problem by reducing the rate of survival of fish spawn. Among other human interventions, are the siltation due to deforestation and merciless catching of brood fish during breeding season attributing to decline of fish populations in wild (Collares-pereira and Cowx, 2004). Moreover, the traditional breeding operations in hatcheries and natural population size reductions have detrimental genetic consequences causing loss of growth potential, disease resistance and stress tolerance. Since 1998, there has been consistent decline in fish production by 2% per year from natural sources in Pakistan (MinFAL, 2007). Wild fish stocks have been heavily overfished, resulting in a noticeable leveling of fish landing during last decade (FAO, 2014). Genetic variation is very necessary as it ensures the fitness and evolvability of population to the ever changing environment (Ullah et al., 2015). Therefore, knowledge on Pak. J. Agri. Sci., Vol. 54(4), 865-872; 2017 ISSN (Print) 0552-9034, ISSN (Online) 2076-0906 DOI: 10.21162/PAKJAS/17.5736 http://www.pakjas. com.pk