Create a new layer: Layer ? New ? Layer and select the Clone Stamp Tool to copy the scales by parts and place them on the girl's skin, sometimes applying also the Eraser Tool of big size and smooth edges.



The fish's layer may be deleted now: Layer ? Delete Layer. The scales must look more real on the shoulder's zone and we need to make it more prominent, passing in a different window: Filter ? Liquefy (shift+ctrl+x) and selecting the Bloat Tool.



Change a little the color of the scales (Selective Color).



The same Clone Stamp Tool will be helpful in placing the scales in several places more.



Change the layer's Blending Mode on Soft Light: