What is maximum sustainable yield and how is it used to manage renewable resources?
Explain maximum sustainable yield and apply it to managing fisheries and other renewable resources
A focused answer to the WACE Year 12 Earth and Environmental Science dot point on maximum sustainable yield. Covers population growth, MSY at intermediate population size, the risk of overexploitation and stock collapse, and management tools such as quotas, with the WA western rock lobster fishery as an example.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
What this dot point is asking
SCSA wants you to explain maximum sustainable yield, why it occurs at an intermediate population size, and how it guides management of renewable biological resources such as fisheries. This is the quantitative core of sustainable management, so be precise about the population logic.
Population growth and yield
A harvested population grows at a rate that depends on its size.
- A very small population grows slowly because there are few breeding individuals.
- A population near its environmental carrying capacity grows slowly because resources limit it.
- Growth is fastest at an intermediate size, where there are enough breeders but resources are not yet limiting.
Because the surplus you can harvest each year equals the population's growth, the largest sustainable harvest, the maximum sustainable yield, comes from holding the population at the intermediate size where growth peaks.
Overexploitation and collapse
Problems arise when harvest exceeds the sustainable yield or when the stock is driven too low.
- Taking more than the annual growth shrinks the population year on year.
- Once the population falls below the fast-growth size, it grows even more slowly, so recovery becomes harder.
- Continued overharvesting can cause a stock collapse, where the population crashes and may not recover, taking the fishery and dependent ecosystems with it.
Managing a fishery
Fisheries management aims to keep harvest at or safely below the sustainable yield despite uncertainty about stock size.
- Catch quotas cap the total allowable catch.
- Size and bag limits protect juveniles so they can breed before being caught.
- Closed seasons and areas protect spawning and let stocks recover.
- Monitoring of catch, effort and stock size feeds back into setting the next quota.
Western Australia's western rock lobster fishery is a well-known example of a managed renewable resource, using catch controls and stock monitoring, and it has been recognised for sustainable management.
Limits of the concept
Maximum sustainable yield is a useful target but a simplification. Real populations fluctuate with the environment, stock size is hard to measure accurately, and fishing exactly at the yield leaves little margin for error. Managers therefore often aim below the theoretical maximum to reduce the risk of collapse.