Prior to modern fishing fisheries were assumed to be at around 100% of virgin stock size. Industrial fishing reduced many inshore fish stocks to very low levels.

A stock size of 40% of the unfished size (B40) is the contemporary estimate of the stock size that will produce the maximum sustainable yield (MSY). B40 is best considered as a minimum stock size, because below this level the stock loses the ability to provide ecosystem services.

B40 has been adopted by Australia, and recommended by the Chief Scientist (Pamela Mace) at Ministry for Primary Industries (MPI) as the most appropriate target for New Zealand. Despite this, MPI don’t adopt this target in the harvest strategies applied to inshore fish stocks.

LegaSea has since updated its policy to align with the New Zealand Sport Fishing Council Manifesto advocating for an amendment to the Fisheries Act to remove ‘maximum sustainable yield’ as the management benchmark and replace it with a target minimum of 50% of the unfished biomass. Read the full Manifesto here.