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Recombinant transformation vectors (ZPβypGH and ZpβrtGH) consisting of fish growth hormone cDNA, and a reporter geneβ-galactosidase driven by fish promoter (Zp) were constructed. Freshly fertilized eggs of zebrafish (Brachydanio rerio) were electroporated at optimum conditions (0.07 kV voltage; 25 μF capacitance; 8 ohm resistance and 2 pulses) in the presence of one of these transformation vectors (100 μg circular DNNml). In either cases 72% of the electroporated eggs successfully hatched, in comparison to the 85% hatchability of the control eggs. Genomic DNA extracted from fins of randomly chosenF ^sub 0^ individuals was screened (by Southern blot hybridization); the transgenes were retained in the host genome of all the randomly chosen adult transformants. Fin-positive presumptive founder parents were crossed with control counterparts and the DNA of randomly chosenF ^sub 1^ progenies was screened for germline transformation. Southern analysis of chosenF ^sub 1^ progenies revealed the persistence of ZPβypGH or ZpβrtGH in 53% of theF ^sub 1^ progenies. Southern analyses of chosenF ^sub 1^ progenies and the frequency (53% ofF ^sub 1^ ZpβrtGH and 53% ofF ^sub 1^ ZP{β}ypGH) of transmission revealed the degree of mosaicism inF ^sub 0^ transformants. Expression was confirmed from the 3-4 times elevated levels of activity of the reporter gene and 30-40% accelerated growth of transgenicF ^sub 0^ andF ^sub 1^ progenies.[PUBLICATION ABSTRACT]