Spawning Stock Biomass (SSB)

Spawning stock biomass is the combined weight of sexually mature individuals in a population, the portion that produces the next generation. It is the biomass quantity most reference points target, since recruitment depends on it: B-MSY and limit reference points are usually expressed as SSB thresholds. Recruitment overfishing is defined precisely as cutting SSB low enough that future year-classes fall, which is why rebuilding plans set SSB recovery targets with deadlines.