Maximum sustainable yield
The largest catch that can be taken from a fish stock year after year without shrinking it.
Also: MSY
A fish stock that is not fished grows until food and space limit it. Fishing thins it out, and a thinner stock can grow faster. Maximum sustainable yield is the catch at the point where that growth is highest, often reckoned at roughly half the unfished size. Many fisheries laws, including those of the European Union and the United States, set it as a target or limit. Critics point out that it is hard to measure, ignores how species affect one another and can be risky if estimates are wrong, so many managers aim to catch somewhat less.