The invention relates to a system and method that enables the capture of high contrast images of sea lice contaminated fish. The system comprises a light emitting device, a 2D array detector, and a first polarisation filter, and utilizes polarised narrow bands of light in order to obtain a strong contrast between sea lice and the skin of the fish. A number of narrow bands of light are irradiated onto a fish, and the resulting reflection(s) is/are polarisation filtered before being detected. The detected light is subsequently used in order to generate a high contrast image of the fish.