Oceans & natural resources
Maximum Sustainable Yield (MSY)
Definition
Maximum sustainable yield is the maximum catch (in numbers or mass) that can be removed from an exploited population over an indefinite period without impairing its capacity to replenish itself. It relies on the surplus production a stock generates when held below its environmental carrying capacity, and occurs at the abundance level producing the greatest surplus. The same logic applies in forestry and wildlife management.
References
definition, surplus production logic, criticisms, fisheries policy use
Overview
What it means
MSY emerged from simple logistic population models, where maximum growth occurs near half of carrying capacity. In practice modern assessments place it around 30% of unfished biomass and treat it as a limit (not a target) on fishing mortality.
How it is used
MSY anchors fisheries law and policy — for example the EU Common Fisheries Policy's objective to restore stocks above MSY biomass levels — and is computed in stock assessments to set catch limits. It is widely criticised for ignoring age structure, ecosystem effects, bycatch and economics.
Why it matters
MSY is the benchmark against which overfishing is defined: roughly a third of assessed global fish stocks are fished beyond biologically sustainable levels, making the concept central to ocean sustainability debates.