1. Production of new weight (biomass) by a fishable stock through growth (G) and recruitment (R) minus the biomass removed by natural mortality (M). SP = G + R - M. When the annual yield is equal to the surplus production, it is an equilibrium yield.
2. Mathematical representation of the way a stock of fish responds to the removal of its individuals (for example by fishing). In fisheries, usually represented by a relationship between yield, cpue, and fishing effort or mortality.
See: Net production .