Not exactly. By allowing these fish to reach their optimal size at maturity, the returning adults will be a variety of sizes and ages. This allows for diversity of body sizes of the females, which allows successful spawning in various locations in the river (e.g., shallow and deep, small tribs and large tribs). This maximizes the use of whatever spawning habitat is available; and optimizes survival.

Plus, if there are various body sizes, the adults will return at different ages. This will spread the risk of adverse weather or geologic conditions (floods, drought, volcanos) across multiple generations. So one bad flood (or Mt. St. Helens) doesn't destroy an entire year class of Chinook.

The bottom line is that harvesting salmon while they are in their feeding/growing stage is destructive on multiple levels. We're better off waiting until they reach their terminal body size before harvesting.