1. The total weight of the living organisms concerned, whether in a system, a stock, or a fraction of a stock: e.g. plankton biomass in an area, biomass of spawners or of newly recruited fish.
2. Or standing stock. Total weight of a resource, a stock, or a component of such stock. Examples: the biomass of all demersal fish on the Georges Bank; the biomass of the cod stock; the spawning biomass (i.e. the weight of mature females).