The international standard for fish stock management is supporting it at a level equivalent to a minimum of 50% of the unfished biomass. Biomass is the combined weight and number of fish in a stock. Unfished biomass is the stock’s estimated natural size. Achieving the standard of 50% of unfished biomass requires managing a stock so that around half the number of fish, or combined weight, remain in the water. This level of abundance is required to ensure the fish are able to fulfil their natural ecosystem functions.