Think of how a projected image follows the contours of whatever it is projected on. This what you would be doing with nurbs curve and nurbs surface.

For the eye, you'll create a nurbs circle (this is the curve to be projected). Then select the fish body (this is your nurbs surface). From the edit curves menu select project curves. You see a circle appear on the surface of the fish. The projected curve is not actually part of the surface, it just matches the surface contours exactly.

Duplicate the projected curve and move it away from fish body, scale it down and repeat until you have all the required circles to make up the eye.

Select all the nurbs circle (except the one that was used for the original project and loft them (this basically stretches a surface over them. Picture the old west covered wagon that had arc frames with canvas stretch over them and you'll understand lofting.