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Referring to organisms living in the spatial water column.
Implemented in the ICES advice on fisheries management in 1998, consisting of a framework of biological reference points, related to upper exploitation boundaries. Management decisions for sustainable fisheries should restrict the risk that the spawning biomass falls below a minimum limit, or that the fishing mortality rate becomes too high. A minimum level of spawning stock biomass, or limit biomass (Blim), is defined. Below Blim there is a higher risk that the stock reaches a level where it suffers from severely reduced productivity. In a similar way a limit of fishing mortality has been defined (Flim). Management should prevent the spawning stock falling below Blim, and avoid a fishing mortality above Flim. To avoid the risk of the spawning stock falling to or below Blim because of uncertainties in the assessment, a higher stock biomass has also been defined - the precautionary biomass (Bpa). To avoid fishing mortality becoming as high as Flim, a lower level of fishing mortality has been defined - the precautionary fishing mortality (Fpa). In general, management advice is aimed at avoiding the risk of the spawning stock falling below Bpa, and the fishing mortality rate increasing above Fpa.