No person called upon to testify as a witness, by or under authority of any court, in any case brought under this chapter, or any law or regulation for the protection of wild animals, birds, or fish shall be excused or exempted from so testifying on the ground that the testimony sought might incriminate him or tend to incriminate him, whether he is called upon to give evidence or produce books, records and papers, but such person shall not thereafter be prosecuted for any offense concerning which he is so called upon to give such testimony or furnish such books, papers, or documents.