A method for directing the displacement of aquatic crustaceans after feeding by utilizing their biological tendency responding to a bright and dark contrast is provided. This method comprises steps to generate the visual effect of this bright and dark contrast at a predetermined place within the water body of culture. Light coming from light emitters directly or from reflection of protrusions and/or painted patterns/figures, and/or filtration of light filters, with the existence of illuminating light, are used for generating visual effect of the bright and dark contrast.