The biggest Bluegill ever caught weighed 5 lbs and 7 oz. It was caught in 1998 by Amos Gray in South Carolina. Majority of Bluegills weigh half a pound. The average length is six to eight inches.Because the term can refer to various types of mussels, freshwater and marine bivalves, determining the size of a clam can be difficult. For example, the giant clam (Tridacna gigas) can be 4 ft long and weigh as much as 440 lbs. The largest clam weighs 507 lbs and measured 53 inches. However, there are also clams that are only a few inches long.