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    Comparative development of larval performance of catfish hybrids (Clarias macrocephalus Gunther x Clarias gariepinus Burchell)
    Cabanos, Cerrone Salamat (Division of Biological Sciences, College of Arts and Sciences, University of the Philippines Visayas, 2003-03)
    Our native catfish, Clarias macrocephalus, is one of the most well-accepted fish in the country. With its soft and savory flesh, this species has high demand in local markets. However, due to its relatively slow growth and poor breeding activity, our native catfish has become rarely used nowadays in aquaculture. This led to the introduction of exotic and faster growing species like the African catfish, Clarias gariepinus, and Thai catfish, Clarias batrachus, which in turn, resulted to the near extinction of the native species. There is therefore a perceived need to undertake a breeding program involving this native catfish and other exotic species. One potential solution to increase our production rate of the native catfish is to hybridize it with the African catfish. Interspecific hybridization has been a popular breeding program utilized by researchers attempting to produce fish expressing hybrid vigor (positive heterosis) or for combining valuable traits from more than one species. This study is on the characterization of the early developmental stages of fertilized eggs and the comparison of larval performance (in terms of percent fertilization, hatching and larval survival) resulting from the artificial cross of Clarias macrocephalus (native catfish) and Clarias gariepinus (African catfish) and its parental species. In comparing the rates of egg development among crosses (all macrolecithal and discoidal cleavage), it was determined that fertilized eggs of the standard hybrid cross (C. gariepinus male x C. macrocephalus female) have a relatively faster rate of development than those from the reciprocal cross (C. macrocephalus male x C. gariepinus female). Results on determination of larval performance showed that there is no significant difference in percent fertilization and percent survival after 7 days between hybrid and parental crosses. However, in terms of percent hatching, the reciprocal hybrid cross (C macrocephalus male x C. gariepinus female), together with the C. gariepinus x C. gariepinus parental cross had a significantly higher percent hatching (P < 0.01) compared to the standard cross (C. gariepinus male x C. macrocephalus female).
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    Comparative growth rates and gross morphology of hybrid catfish Clarias gariepinus (female) x Clarias macrocephalus (male)
    Agase, Mark Christian A. (Division of Biological Sciences, Bachelor of Science in Biology, University of the Philippines Visayas, 2004-03)
    Catfishes are among the groups that has been considered economically important fishes in the Philippines and in other countries. The freshwater catfish Clarias macrocephalus is native to the Philippines but it is becoming scarce in many natural habitats. It is a favorite food dish due to its tender and delicious meet. Aquaculturists these days focus more their attention to the culture of exotic species like Clarias gariepinus and Clarias batrachus that in turn resulted to the near extinction of the native species. There is therefore a need to undertake a breeding program involving this native catfish and other exotic species.A 12-week study was conducted to compare the growth rates of the hybrid catfish C. macrocephalus (♂) X C. gariepinus (♀) in natural ponds and laboratory rearing conditions. In addition, the length-weight relationship was also determined. Gross morphology was also noted in the experiment.Results showed that the trend for SGR of the hybrid in natural pond and laboratory rearing conditions from weeks 2 to 12 is decreasing. Continued feeding of the hybrids on artificial diets results in poor fish growth. T-test revealed that there is a significant difference on the SGR for both the length and weight with hybrids in natural pond rearing conditions being consistently higher than the laboratory set-up.From the linear regression equation, there was no homogeneity of regression, coefficients, or slopes in the mean body lengths (MBL) and mean body weights (MBW) of me hybrids in the natural pond and laboratory rearing condition. It simply means that there is a significant difference on the growth rates of the hybrid as to the type of environment they are reared. The product-moment correlation showed that there is a linear relationship between the length and the weight of the hybrid fish, 7.9305378 X 104 being the constant. Gross morphology of the hybrids includes the appearance of a trident-shaped occipital process, which was not pointed and narrow as in the case of the parent C. gariepinus. A turtle shell-like design arranged bilaterally characterizes the dorsal side of the head. A modification of the dorsal fin was also noted as to the presence of the adipose fin at the posterior end of the dorsal fin, which was about 3-5 mm in length.