Unit Stock

A unit stock is a fish population, or part of one, defined as a single biological entity for assessment and management because its demographic rates and harvest can be treated as self-contained. The unit ideally matches a reproductively isolated population with its own recruitment, growth, and mortality, so that catch from one area does not draw down a separate breeding group. In practice managers set the boundary on the available stock-structure evidence, and genetic stock identification tests whether the unit holds. A unit stock that lumps distinct populations hides local depletion; one split too fine wastes assessment effort.