The application of a number theory based pseudorandom sequence called Partial Quotient (PQ) sequence generated from the continued fraction expansion of irrational numbers in a semi fragile watermarking scheme for content based image authentication is considered in this paper. The generated pseudorandom PQ sequence is used to create sub vectors to be used at various instances in the watermarking process. The watermark is derived from the image replica handbags and is embedded in the higher textured blocks. The watermarked images demonstrate high imperceptibility and make it suitable for use in artistic, medical and military applications where high quality and minimal distortion of the watermarked images is required