Taxonomic Revision of the Tiger Fish <i>Hydrocynus vittatus</i> (Castelnau, 1861), <i>H. Brevis</i> (Cuvier & Valencience, 1849) and <i>H. forskalii</i> (Cuvier, 1819) from the Nile in Sudan

Abstract

The main objective of this study was to revise the taxonomic status of three species from the genus Hydrocynus : H. vittatus (Castelnau, 1861), H. brevis (Cuvier & Valencience, 1849) and H. forskalii (Cuvier, 1819), commonly known as Tigerfish to determine the morphological characters for distinguishing them. The study was based on morphometric and meristic characters plus body weight of specimens. Analysis of morphological characters was done by the statistical programme “PAST”. The study also considered the length – weight relationships and the type of growth for each species. Twenty morphometric characters had almost equal loads, ranging between (-0.1843 and -0.2436) in separating the three species. The number of lateral line scales, LLS, had the biggest load of (-0.9994) followed by the number of teeth in upper jaw, UJT (-0.5643), the pectoral fin rays, PFR (-0.4638), gill rakers, GR (-0.4596) and the number of teeth in lower jaw, LJT (0.3471). The morphological results indicated that a combination of morphological characters can be used to separate the three species of the genus Hydrocynus . They may also be distinguished by the position of the dorsal fin compared to insertion of the ventral; the black-edge of the dorsal and adipose fins and the black-edge fork caudal fin of H. vittatus ; and the reddish-orange lower caudal-fin lobe and the red anterior area of anal fin of H. brevis . The length-weight relationship was W = 3.088 L -2.079 for H. vittatus and (r 2 = 0.923); W = 3.451 L -2.534 for H. brevis and (r 2 = 0.664); W = 2.9981L -1.9815 and (r2 = 0.418) for H. forskalii . The values (b = -2.079, -2.534 and --1.9815) indicated allometric growth of the three species. There was a strong positive correlation between standard body length and body weight of H. vittatus . It is recommended that morphological analysis should be compared and combined with biochemical and molecular phylogenetics.