Degree of intraspecific genetic divergence and variability in three Sciaenid species

Abstract

Abstrllct Genetic variations in Nibea mitsukurii, N. albijfora and Pennahia argentara from different localities were assayed electrophoretically. The genetic variability in N. mirsukurii was relatively high. According to the chi-square values for heterogeneity between two localities and genetic distance (D) values, N. albijfora from the Ariake Sea and the Inland Sea or the East China Sea (D=O.OO92 in average), and N. misukurii, from Tosa Bay vs, Atsumi Bay (D=~O.OO67) were considered to be independent subpopulations, The D value in N. albifiora from the Inland Sea VS, the East China Sea was quite small (D=O.OOlO), In P. argenrara populations, the D values were also small. Further, the relationship between genetic and geographic distances observed in the three species were discussed, P. argenrata showed a positive relationship between these two factors as compared to N. mirsukurii or N, albifiora. It seemed that the lower level of genetic divergence might be due to the frequent gene flow within the large-scale and wide distributional range of the population. During the past decade the application of gel electrophoresis coupled with selective enzyme stain­ ing has shown that a large amount genetic variation exists in natural populations of many species (Allen­ dorf and Utter, 1979). Phenotypes of allozyme can be scored during most stages of their life cycle and their genetics more easily interpreted than the pro­ portional and meristic characters employed in fish taxonomy. Genetic differences among populations within a defined body of water may conceivably decrease with time, due to gene flow by migration within sub­ populations. Alternatively, genetic differentiation could become· accentuated through time, perhaps because subpopulations become increasingly associ­ ated with discrete breeding areas (Felley and Avise, 1980). The fishes of the family Sciaenidae contribute sub­ stantially to the fisheries of the warm and shallow seas and estuaries of the world. Nibea mitsukurii (Jordan et Snyder) commonly known as nibe croak­ er, extends along the coast of the Pacific Ocean from Sendai Bay in the north to Hyuga Basin (an open bay) in the south. Nibea albiflora (Richardson), commonly known as roncader, occurs in Hong­ kong, the East China Sea and northwards to Port Arthur and southern Japan. Pennahia argentata (Houttuyn), commonly known as white croaker, is widely distributed in Japanese, Korean and Chinese waters (Trewavas, 1977).