Abstract
Morphometric characterization using truss network systems has been widely used for fish identification and stock identification. In Sri Lanka, differentiation of Oreochromis mossambicus and O. niloticus, the two major species in reservoir fishery, using conventional morphometric characteristic and phenotypic variations is problematic, due to the reasons that both species share somewhat similar body shape characteristics and that the populations of the two species have mixed characteristics as a result of introgressive hybridization. In the present study, an attempt was made to employ truss network analysis to differentiate O. mossambicus and O. niloticus. Truss measurements of 100 specimens of O. mossambicus from Negombo lagoon and 100 specimens of O. niloticus from Baira lake were analyzed using principal component analysis (PCA). Before the analysis, two approaches of data transformation were employed to minimize to eliminate any size effect in the data set of truss measurements. It was concluded that the data standardization method using a geometric mean regression techniques on the logarithms of truss length and total length was more effective for morphometric differentiation of the two cichlid species than using ratio of truss length to standard length for data transformation. DOI: http://dx.doi.org/10.4038/sljas.v16i0.6705 Sri Lanka J. Aquat. Sci. 16 (2011): 01-10
Highlights
Morphometric characterization is a powerful tool in fish taxonomy
The morphometric data transformed as LT/SL, and those which were standardized for fish size using equation (2), were subjected to pair-wise comparison separately
In O. mossambicus out of 153 pairs, only one (0.65%) was significantly correlated while in O. niloticus, zero pairs (0%) were significantly correlated at least at 0.05 probability level
Summary
Morphometric characterization is a powerful tool in fish taxonomy. Conventional morphometric analyses such as length-weight relationships are not sufficient for morphometric characterization of fish species which are more or less morphometrically similar. A system of morphometric measurements called “Truss Network System” (Strauss and Bookstein (1982) has been increasingly used for species identification and especially for stock differentiation (Turan 1999). Sci. 16 (2011): 01-10 reported on the use of TN system for quantifying shape characterization of fish. Multivariate analysis was performed using truss morphometrics to study the differences among 6 species of family Serranidae (Cavalcanti et al 1999). Strauss and Bookstein (1982) have compared traditional morphometric character sets of Cottus kalamathensis and Cottus pitensis and have shown that truss character sets were more effective than traditional character sets Multivariate analysis was performed using truss morphometrics to study the differences among 6 species of family Serranidae (Cavalcanti et al 1999). Strauss and Bookstein (1982) have compared traditional morphometric character sets of Cottus kalamathensis and Cottus pitensis and have shown that truss character sets were more effective than traditional character sets
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