Section 51A. No retail establishment or person shall sell or represent for the purpose of sale, any item as crabmeat unless the same is from crustaceans of any species of crab, so-called. A retail establishment or person selling a product which contains crabmeat in any proportion shall list separately the names and percentages of all noncrabmeat substances contained therein. A violation of any provision of this section shall be punishable by a fine of not less than fifty nor more than five hundred dollars.