Definition
Maximum sustainable yield for fishing
The Maximum Sustainable Yield (MSY) is the highest possible annual catch that can be harvested indefinitely without depleting a fish population.
- Maximum Sustainable Yield (MSY) is the largest long-term average catch or yield that can be taken from a natural population under constant environmental conditions without reducing its capacity to replenish.
- It is a biological reference point used in managing renewable resources such as fish stocks, forests, and game animals.
- MSY represents a balance between population growth and harvesting rate, ensuring sustainability over an indefinite period.
- Think of MSY like a savings account.
- If you only withdraw the interest (growth) each year, the balance (population) remains stable; withdraw too much, and the account (ecosystem) declines.
MSY aims to maintain populations at a size that allows maximum growth rate, typically around half the carrying capacity (K/2).
Relationship Between Sustainable Yield (SY) and MSY
- Sustainable Yield (SY) is the rate of increase in natural capital that can be exploited without diminishing the original stock.
- MSY is the highest possible sustainable yield, the maximum point before overexploitation begins.
SY = (Annual growth and recruitment) − (Annual death and emigration)
ExampleIn a fish population, if 1,000 new fish are born each year and 200 die naturally, the sustainable yield is 800 fish per year. Catching more than that would reduce the population.
How MSY Works in Fisheries
- Fisheries managers aim to harvest the same number of fish as are naturally added through growth and reproduction.
- This maintains the fish population at a stable equilibrium, avoiding collapse.
- If harvest = population growth rate → fish stock remains stable
- If harvest > growth rate → overfishing and decline occur
- If harvest < growth rate → underutilization (potential yield wasted)
- In a fish population where 10,000 new fish are born each year, catching 10,000 fish annually maintains a stable population.
- This is the MSY level.
