PROCESSING PLANT #2. Block frozen 10KG carton. BUTTERFISH are dull blue on the top, with pale sides and a silvery belly. Numerous irregular dark spots fade after they are harvested. Very thin and deep-bodied, like a flounder set upright, and somewhat circular or rounded. Small mouths with weak teeth and blunt noses. 6 to 9 inches in length, though some individuals can reach 12 inches. Up to 1.25 pounds in weight. BUTTERFISH are short-lived and grow rapidly. Few live to more than 3 years of age, and most are sexually mature at age 1.