Section 28. The proprietors of lands upon which a pond is created and maintained by excavating and enclosing the same and by the artificial flowing of same with coastal waters, for the purpose of cultivating and maintaining fish thereon, shall have the exclusive rights to cultivate and the exclusive ownership and control of, all fish thereon or therein, whether artificially or naturally propagated; provided, that no fish determined by the director to be injurious may be cultivated or maintained thereon or therein, and that no fish may be taken therefrom of a size, of an age, at a season, or for a purpose, prohibited by law; and provided, further, that before any such excavation shall be made plans for an artificial flowage of the same with coastal waters shall be approved by the director and the department of environmental protection.