The impact of a fishery on a stock is a combination of the amount
of catch and the size composition of the fish that are caught. Catching
a given tonnage of juvenile fish may not have the same impact
on the stock abundance as capturing the same tonnage of sexually
mature fish, so it is important to account for both the amount of
fish caught and the size composition of those fish when estimating
the impact of a fishery. In addition, the maximum sustainable yield
(MSY) obtainable from a stock of fish is dependent upon the size
composition of the fish caught (Goodyear, 1996; Maunder, 2002);
in general, the greatestMSYs are obtainable when the catch consists
mostly of fish of intermediate sizes.