EE Lecture 32: Population Management

Question 1

name some species that have been helped through popn management

Answer 1

the golden lio tamarin

saiga antelope in russia

Question 2

using the logistic growth model, when is there max growth

Answer 2

when K =50%

Question 3

in what species is recruitment constant

Answer 3

icelandic cod

Question 4

in what species does recruitment appear to decline at lower density than others

Answer 4

N Sea Herring
NE Arctic cod
due to weak regulation

Question 5

what is MSY

Answer 5

the max sustianable yield (peak of net recruitment “n shape” curve, suppresses the popn level differently, depending on the curve

Question 6

what do net recruitment curves show

Answer 6

how many new individuals are added per unit time at each level of pop
how much you can harvest per unit time at each level of the pop without further decreasing the pop

Question 7

how can you infer whether a popn will grow or shrink

Answer 7

by plotting the harvesting strategy and the recruitment curve together

Question 8

at a given popn level N, if the harvesting strategy line is lower than the recruitment curve, what happens to popn

Answer 8

popn grows

Question 9

at what given popn level does popn grow

Answer 9

if the harvesting strategy line is lower than the recruitment curve

Question 10

at a given popn level N, if the harvesting strategy line is higher than the recruitment curve

Answer 10

pop shrinks

Question 11

at what popn level does popn shrink

Answer 11

if the harvesting line is above the recruitment curve

Question 12

what happens to pop level N if recruitment curve and harvesting curve are equal

Answer 12

the popn stays the same

Question 13

what is a stable eqbm

Answer 13

the recruitment curve is lower than the harvesting strategy to the right, highter to the left

Question 14

what is the break point

Answer 14

the recruitment curve is higher than the harvesting strategy to the right, lower to the lefft

Question 15

what are the dangers of a fixed quota harvesting strategy @ MSY if you know MSY exactly

Answer 15

the popn is only going to an unstable eqbm

eventual extinction, because of random variation

Question 16

what are the dangers of a fixed quota harvesting strategy if you overestimate MSY

Answer 16

extinction occurs automatically without random factors

Question 17

what is unstable eqbm

Answer 17

recruitment is lower both sides (@ peak)

Question 18

what eqbm is it when ercruitment is lower to the left

Answer 18

break point

Question 19

what eqbm is it when recruitment is lower both sides

Answer 19

unstable eqbm

Question 20

what eqbm is it when recruitment is highter to the left

Answer 20

stable eqbm

Question 21

which type of recruitment is safer

Answer 21

stable recruitment because even if the population is lower than predictions, recruitment is still higher

Question 22

give an example of where fixed quota systems have been dangerous if you dont extract the whole MSY from the system

Answer 22

Peruvian anchovy fishery
used to be biggest in world - said MSY was 10mill tonnes/yr, catch fixed @10mill - stocks plunged - until industry collapsed`

Question 23

`what is a harvesting strategy

Answer 23

an amount that you plan to take, depending on the popn level - a plot of planned offtake vs pop size

Question 24

what is a fixed quota system

Answer 24

fixed offtake, regardless of pop size

Question 25

what is a fixed effort system

Answer 25

proportional offtake (% of existing pop per year)

Question 26

which system takes a proportional amount off pop per year

Answer 26

fixed effort system

Question 27

which system takes % off pop regardless of pop size

Answer 27

fixed quota system

Question 28

what is eqtn for fixed effort harvesting strategy @ MSY

Answer 28

H = q * e * N
H - harvest
q - efficiency
e - effort
N - pop/stock size

Question 29

what does eqtn for fixed effort harvesting strategy do

Answer 29

predicts a straight line wrt N

Question 30

when is illegal harvesting more common

Answer 30

when quotas are low - when popns sare low

Question 31

what are breakpoints examples of

Answer 31

tipping point behaviour - if the system crosses the tipping point, it goes to a new stable state and then it can be very hard to bring it back to the original state

Question 32

how long did the recovery of Peruvian anchovies tak

Answer 32

20yrs

collapse of the whole exploiting industry

Question 33

what are dangers of MSY

Answer 33

ignores variation in pop
harvesting is predominantly on certiain individuals eg. bigger/larger
it ignores enviro