Sustainable Harvesting Flashcards
What is the MSY?
Maximum Sustainable Yield. Based on biomass vs growth rate. Maximises yield so top is the maximum sustainable (K/2).
This is where the population can grow maximally, to replace those lost. At half the carrying capacity.
Below K/2, when individuals are lost there is a risk of extinction.
Above K/2, there is over compensation
What is a low quota harvest?
The harvest size is independent of population size as removing a certain size.
There are two points where a sample size of h crosses the graph.
If at the left, will move the population to extinction. If at right, will increase population size back to normal.
Means it is critical to know the numbers in the population.
What is a high quota harvest?
Pushes the species to extinction.
Peruvian anchovy fishing example?
The most heavily exploited fish in world history.
Top yield was 13.1 million tonnes in 1971, has undergone great fluctuations over time.
The population was greatly reduced by overfishing and the 1972 El Nino event.
In 2008-2012, the annual catches varied between 4.2 and 8.3 million tonnes, which is consistently more than for any other fish species harvested in the wild.
Drove the population almost to extinction. Huge socio-economic implications in Peru.
How should the MSY be modified?
Only take catch if the population is above a certain size.
What is the effort model?
In population ecology and economics, optimum sustainable yield is the level of effort (LOE) that maximizes the difference between total revenue and total cost. Or, where marginal revenue equals marginal cost.
This level of effort maximizes the economic profit, or rent, of the resource being utilized. It usually corresponds to an effort level lower than that of maximum sustainable yield.
In environmental science, optimum sustainable yield is the largest economical yield of a renewable resource achievable over a long time period without decreasing the ability of the population or its environment to support the continuation of this level of yield.
What is the paradox of enrichment?
Can enrich the environment with fertiliser.
May now be to the left of the MSY, and pushes the population into different dynamics.
What is the tragedy of the commons?
One person can affect everyone else.
If everyone does one thing, can result in overgrazing.
Whats good for individual vs group.
Game theory approach - best to act selfish as an individual
Why are fisheries a good example of the tragedy of the commons?
- Resources are finite and exploitation exceeds natural capacity for population
- Resources are collectively owned by society (common property)
- Users act selfishly, even against community’s best interests
Solutions:
- Resources are privatised
- Resources are government owned and regulated
- Resources are controlled by local communities
How do we value a resource?
Direct - food or pharmaceutical
Indirect - recreational
Existential - knowing a resource exists
Cost benefit analysis?
Costs vs benefits of taking a resource.
Immediate vs future benefits of resource
