Growth rate (replacement) and size of the fish
stock/pool
• Too Small/Low Stock Size
• Lower growth rate as fish can’t hook up and reproduce
• Birth (replacement) less than death/harvest
• Growth rate declines; species becomes extinct
• Too Large Stock Size
• Food sources (plankton, biomass, other fish) too small to support large # of
fish
• Growth rate declines
Schaffer model: Relationship between the Fish Population and
Growth
3 Possible Solutions
• 1.
Open (unregulated) Fisheries (Ec)
• Catch until total costs exceed revenues (up to zero profits) => ATC(Q) =
TotRev(Q) = P*Q
• 2.
Maximum Sustainable Yield(MSY) (Em)
• Largest “harvest” that can be sustained every year (harvest = replacement
rate)
• Biologist solution
• 3. Economically Efficient (Eo)
• Maximize Economic Value MC(Q) = MR(Q)
FIGURE 14.2
Efficient Sustainable Yield for a Fishery