The more I think about your think about your fish the harder I think it will be to do, there are a number of things that are going on with a fish scale like yours, some of the colour will come from the scale, some from the reflective colour and some from the transparency of the scale showing the body colour. Give the ramp shader a go but also bring some transparency into it...............dave

Edit: there is a bump slot and you can use the texture layer shader to have a texture under your scales texture