70 Rudhy Gustiano Indonesian Journal of Agricultural Science 5(2) 2004: 70-74 ABSTRACT It is really important, since the possible use of these pangasiid hybrids in aquaculture faces the problem of potential impact on wild population. Therefore, it is urgently needed to provide quick identification tools in the field. This study investigated morphol- ogical characters of Pangasius djambal and Pangasianodon hypophthalmus and their hybrids. A detailed morphological analysis using 32 morphometric measurements and five meristic counts was done on the hybridization of P. djambal and P. hypophthalmus. Morphometric analysis and meristic counts showed that the reciprocal hybrids have intermediate characters except for gill raker number in which lower than that of parental species. In general, the hybrids have tendency to be like P. hypophthalmus rather than P. djambal. The only typical charac- ter of P. djambal appeared on hybrids is teeth shape, both vomerine and palatine. It is clearly defined that the true hybrids have seven pelvic fin rays. [Keywords: Pangasius djambal, Pangasianodon hypophthalmus, hybridization, biometry] INTRODUCTION Catfishes of the family Pangasiidae are of great economic importance in Southeast Asia region such as Pangasius djambal in Indonesia (Legendre et al . 2000), P. bocourti in Vietnam (Hung et al. 1999), and Pangasianodon hypophthalmus (senior of P. sutchi ) (Tarnchalanukit 1986). Thus, many efforts of breeding practices have been done to increase their production. As interspecific cross-breeding in fish may lead hybrid with valuable characteristics for aquaculture (sterility, monosex population, heterosis or growth etc.), it was decided to evaluate the effect of hybrid vigor on the artificial hybridization in pangasiid catfishes. In contrast with the abundant literature on the hybridization in other cultured fish families, in particular cichlids, salmonids, cyprinids and ictalurids (for review see Sneed 1971; Moav 1976; Chevassus 1979, Wohlfart and Hulata 1981; Chevassus 1983), reports on hybridization of pangasiid catfishes are rather scarce. Enzymatic system (protein total) allowed to differentiate easily and quickly P. djambal from P. hypophthalmus: allele 100 for locus Prot1 and allele 105 for locus Prot2 for the first species, while allele 100 for Prot1 and alleles 100 and 150 for Prot2 (Legendre et al. 2000). However, there is no genetic data available for the hybrids so far. Therefore, it is really important to provide quick identification tools in the field since the possible use of these pangasiid hybrids in aquaculture faces the problem of potential impact, genetic deterioration, on wild population. This study investigated morphological characters of P. djambal and P. hypophthalmus and their hybrids. MATERIALS AND METHODS Specimens examined in this hybridization experiment consisted of 114 specimens of P. djambal (142-635 mm), 31 specimens of P. hypophthalmus (147-630 mm), 45 specimens of hybrids of female P. djambal x male P. hypophthalmus (133-490 mm), and 45 specimens of hybrids of male P. hypophthalmus x female P. djambal (129-473 mm). Specimens of P. djambal were collected from the main rivers in Java, Sumatra and Kalimantan (Indonesia), while those of P. hypophthalmus mostly originated from fish culture in Mekong River (Viet- nam) and in West Java (Indonesia). Specimens of P. djambal and P. hypophthalmus were deposited in the Museum Zoologicum Bogoriense (MZB), Cibinong, Indonesia, and in the Muséum National d’Histoire Naturelle (MNHN), Paris, France. All of the hybrid specimens originated from artificial breeding per- formed at Research Institute for Freshwater Fisheries (RIFF) station in Sukamandi, West Java, Indonesia. Specimens of P. djambal and P. hypophthalmus were identified following Gustiano (2003). Body length was measured using a graduated ruler of 1 m. Thirty two measurements were made using dial BIOMETRIC ANALYSIS OF THE ARTIFICIAL HYBRIDIZATION BETWEEN Pangasius djambal BLEEKER, 1846 AND Pangasianodon hypophthalmus SAUVAGE, 1878 Rudhy Gustiano Research Institute for Freshwater Aquaculture, Jalan Sempur No. 1, Bogor 16151, Indonesia Short Communication