Lecture Six - Sustainable Harvesting & Exploitation

Question 1

What is exploitation?

Answer 1

Taking what’s out there.

Question 2

What is harvesting?

Answer 2

Taking something you put there.

Question 3

When fisheries collapse, what happens to the price of the fish?

Answer 3

They become more expensive

Question 4

What is the definition of a fishery collapse?

Answer 4

Dropping below 10% of the recorder maximum.

Question 5

What percentage of fished species were considered collapsed in 2003?

Answer 5

29%

Question 6

What is Maximum Sustainable Yield?

Answer 6

The maximum level at which a natural resource can be routinely exploited without long-term depletion.

Question 7

Give the classifications of stocks, depending on how far away they are from MSY.

Answer 7

• Underexploited (U)
• Moderately exploited (M)
• Overexploited (O)
• Depleted (D)
• Recovering (R)

Question 8

Give the equation for population change over time.

Answer 8

= R Nt

Where R is a constant, and Nt is population size.

Question 9

When is there no population change?

Answer 9

When birth rate = mortality rate.

Question 10

When is R at maximum?

Answer 10

When there are no births and no deaths.

Question 11

What is the effect of each extra individual in the population?

Answer 11

Each extra individual in the population depresses everyone’s expression of R by a small fraction.

Question 12

Give the equation for population change, with extra individuals taken into account.

Answer 12

RNt ( [ K - Nt ] / K )

Question 13

Give the equation for yield, and the assumption this equation holds.

Answer 13

Yield (Y) = Effort (E) x Number of fish there (N)

Assumption: the more fish you go out to catch, the more you capture.

Question 14

When are MSYs under stable equilibria?

Answer 14

Under intermediate levels of exploitation

Question 15

Give the equation for the equilibrium population size.

Answer 15

N = K - ( K/R x E )