Except as provided in Section 20-90 no person shall buy, sell or barter, or offer to buy, sell or barter, nor shall any commercial institution or any regularly operated refrigerated storage establishment have in its possession, aquatic life protected by this Code except those species taken under the conditions and of the size described in Sections 15-55 and 15-60 and administrative rules pertaining to the taking of commercial fish or mussels. Any person who is found guilty of violating this Section shall be guilty of a Class A misdemeanor.