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The abundance, occurrence, biological features, growth and mortality parameters of the thornback ray, Raja clavata L. 1758 (Rajformes, Rajidae), coming from two contiguous areas of the Strait of Sicily (Central Mediterranean Sea) were analysed in order to discriminate the stocks. The two investigated areas include bottoms off southern Sicily (I-G16) and bottoms further at large (O-G16). The density indexes, biomass indexes and occurrences were substantially lower in I-G16 than O-G16. On the contrary, the biological traits were more similar, although significant differences were detected in the sex ratio, in the median total length of all specimens, in the length frequency distribution, in the estimated maximum length and in the female length-weight slope parameter. The median length of fully mature specimens did not significantly differ between the two areas. The von Bertalanffy's asymptotic length and the ratio of total mortality/von Bertalanffy's curvature parameter suggest a total mortality higher in the I-G16 than the O-G16 populations. This article supports the hypothesis that the investigated populations, in spite of a similar original life cycle, have evolved in two distinct unit stocks as a consequence of the different fishing efforts and the low-intermingling rate between the two areas. [ABSTRACT FROM AUTHOR]