A method and system for monitoring and control of ectoparasites of fish based on optical fluorescence where a fish potentially infested with ectoparasites is optically illuminated using an optical excitation source (220) with spectral composition capable of exciting optical fluorescence in said ectoparasites. The optical fluorescence is detected using one or more optical detectors (223) together with appropriate spectral filters (222) arranged to detect substantially only the optical fluorescence from said one or more ectoparasites. The ectoparasites can be removal by use of directed acoustic or optical radiation.
