High levels of genetic variability and differentiation in hilsa shad, Tenualosa ilisha (Clupeidae, Clupeiformes) populations revealed by PCR-RFLP analysis of the mitochondrial DNA D-loop region

Sabuj Kanti Mazumder,Md Samsul Alam

doi:10.1590/s1415-47572009005000023

Sabuj Kanti Mazumder, Md Samsul Alam

Open Access

https://doi.org/10.1590/s1415-47572009005000023

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Abstract

The hilsa shad, Tenualosa ilisha (Clupeidae, Clupeiformes) is an important anadromous clupeid species from the Western division of the Indo-Pacific region. It constitutes the largest single fishable species in Bangladesh. Information on genetic variability and population structure is very important for both management and conservation purposes. Past reports on the population structure of T. ilisha involving morphometric, allozyme and RAPD analyses are contradictory. We examined genetic variability and divergence in two riverine (the Jamuna and the Meghna), two estuarine (Kuakata and Sundarbans) and one marine (Cox's Bazar) populations of T. ilisha by applying PCR-RFLP analysis of the mtDNA D-loop region. The amplified PCR products were restricted with four restriction enzymes namely, XbaI, EcoRI, EcoRV, and HaeIII. High levels of haplotype and gene diversity within and significant differentiations among, populations of T. ilisha were observed in this study. Significant FST values indicated differentiation among the river, estuary and marine populations. The UPGMA dendrogram based on genetic distance resulted in two major clusters, although, these were subsequently divided into three, corresponding to the riverine, estuarine and marine populations. The study underlines the usefulness of RFLP of mtDNA D-loop region as molecular markers, and detected at least two differentiated populations of T. ilisha in Bangladesh waters.

Highlights

The hilsa shad, Tenualosa ilisha, belonging to the sub-family Alosinae of the family Clupeidae (Clupeiformes, Pisces), occurs in foreshore areas, estuaries, brackish-water lakes and freshwater rivers of the western division of the Indo-Pacific faunistic region
The purpose of the present study is to examine the usefulness of mitochondrial D-loop region diversity to supplement allozyme and RAPD data on the population genetic structure of T. ilisha
The detection of 35 different haplotypes in only 90 individuals of five T. ilisha samples underlines the usefulness of RFLPs of the D-loop region as molecular markers for investigating the geographic structure of the species

Summary

Introduction

The hilsa shad, Tenualosa ilisha, belonging to the sub-family Alosinae of the family Clupeidae (Clupeiformes, Pisces), occurs in foreshore areas, estuaries, brackish-water lakes and freshwater rivers of the western division of the Indo-Pacific faunistic region. Hilsa shad is the largest single fishable species in Bangladesh, present in almost all the major river systems, estuaries and marine environments (Bay of Bengal), and at present contributing to approximately 12% of the total fish production and 20% of fishery-capture (inland and marine) with a biomass of 78, 273 metric tons from inland fisheries and 198, 850 metric tons from marine (DoF, 2006). Fishery has entered into a severe decline upstream and is nowadays mainly concentrated downstream, as well as in estuaries, coastal areas and the sea (Nurul Amin et al, 2004). Due to the low water discharge from the upstream Ganges at the Farakka barrage (in West Bengal, India) with the consequent heavy siltation, the indiscriminate exploitation of juveniles (Jatka), disruption of migration routes, loss of spawning, feeding and nursing grounds, increased fishing pressure, etc., have all contributed to this decline

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