It has been postulated that the building of the Shahid-Rajaei dam on the Tajan River around 1995 has lead to the morphological divergence of Siah Mahi Capotes capoeta gracilis (Pisces) of up-and downstream populations due to the isolation. A 13-landmark morphometric truss network system was used to investigate the hypothesis. Univariate analysis of variance showed significant differences between the means of the two groups for 45 standardized morphometric measurements out of 78 characters studied. In linear discriminant function analysis (DFA), the overall assignment of individuals into their original groups was 87.6%. The proportion of individuals correctly classified into their original groups was 90.3% for upstream and 83.7% for downstream population. The principal component analysis (PCA) scatter plot of individual component scores between PC1 and PC2 showed 121 fish specimens grouped into two areas but with a relativity high degree of overlap between two populations. Clustering analysis based on Euclidean square distances among groups of centroids using an UPGMA resulted into two main clusters indicating two populations of C. c. gracilis. The present study indicated the presence of two morphologically different populations of C. c. gracilis in the Tajan River across the Shahid-Rajaei dam, probably due to their limited downstream dispersal and the elimination of upstream migration altogether, due the construction of the dam.

No abstract

No abstract

a b s t r a c tDecapterus russelli (Indian Scad) is an important pelagic carangid distributed on both east and west coast of India. Despite its wide distribution, the stock structure of the species is not well known. The present study was conducted to investigate stock structure of D. russelli, based on body shape morphometrics using truss network system. A total number of 360 samples of the species were collected from two centres, Digha and Visakhapatnam in Bay of Bengal from east coast and on the west coast from Mumbai and Cochin in Arabian Sea. A truss network was constructed by interconnecting 11 landmarks to form a total of 23 distance variables extracted from digital images of samples using tps Dig2 and PAST software platforms. The transformed truss measurements were subjected to factor analysis and classification by cross-validation of discriminant analysis. Factor analysis showed meaningful loading of the middle portion, the portion below the second dorsal fin, above anal fin, and the caudal portion on first and second factor, respectively. The factor analysis revealed the existence of two morphologically different stocks of D. russelli between east and west coast of India. The discriminant analysis was conducted by the combination of the truss distances that loaded on Factor-1 and Factor-2. The measurements that belonged to the middle portion and caudal portion of the body produced minimum misclassification rate of 5% between the coasts; whereas, the misclassification was 28% for all the four stocks. The misclassification was higher between the stocks within the coast. The high rate of misclassification observed within the coast is probably the result of no demarcation in fishing area. The occurrence of a separate stock on each coast may be the result of different physical and ecological condition of Bay of Bengal and Arabian Sea.

A new fish species, Stolephorus tamilensis sp. nov., is described from the East coast of India. The major distinguishing characters are 5–6 small needle-like pre-pelvic scutes on belly; maxilla tip pointed, reaching to border of operculum, concave and indented in the preoperculum; 25–28 gill rakers on lower lobe of the first branchial arch; dorsal fin without spine; 17–19 anal-fin rays. Moreover, S. tamilensis sp. nov. present higher average genetic divergence values at mitochondrial cytochrome c oxidase subunit I and 16S rDNA loci in comparison with congeners. Also, nucleotide diagnostic characters exclusive to S. tamilensis are identified. Neighbor-joining analysis revealed close relation between S. tamilensis  and S. andhraensis.