Quiz 8

Question 1

Density dependent: Compensatory

Answer 1

-per capita recruitment declines with increasing size of spawning stock

Question 2

Density-dependent: Overcompensatory

Answer 2

• recruitment really declines with high stock

- EX: when cannibalism occurs, or disease outbreaks due to overcrowding

Question 3

Density-dependent: Depensatory

Answer 3

-per capita recruitment drops when stock goes below a certain level

Question 4

Density-dependent model: Beverton-Holt model

Answer 4

R = @S/B+S

• alpha times stock dived by beta + stock
• as S gets large, R approaches alpha
• one of the more freq used models

Question 5

Density dependent model: Ricker model

Answer 5

R=@Se_(-BS)

• alpha is the slope of the curve near 0
• as S gets large, e-(-BS) gets very small
• one of more freq used models

Question 6

Error that can occur when measuring stock size

Answer 6

measurement error

Question 7

How can fish stocks recover

Answer 7

-overfishing must be ceased

Question 8

Hilborn and Walters warnings

Answer 8

• Warning 1: do not blindly believe the average behavior predicted by models
• Warning 2: do not ignore the variability in the real data - use it to generate estimates of variance

Question 9

Carrying capacity

Answer 9

K = (b_0 - d_0)/(a+c)

-represents the max pop size supportable in a given environment

Question 10

Logistic growth model

Answer 10

(dN/dt) = rN(1 - (N/K))
1 - (N/K) is the “unused portion of carrying capacity
-created by P. F. Verhulst

Question 11

Assumptions of the logistic model

Answer 11

• no time logs
• no migration
• no genetic variation
• no age structure in pop
• K is constant

Question 12

Stable limit cycle

Answer 12

• When (r * t) is greater than 1.57

- pop oscillates up and down in regular cycles

Question 13

Discrete population growth model

Answer 13

• breaks up time into discrete chunks

- keeps track of time chunks by calling them t

Question 14

Robert May

Answer 14

-famous ecologist that studied time-lagged and discrete versions of the logistic growth model

Question 15

Chaos

Answer 15

-situation where the model is extremely sensitive to the initial starting conditions

Question 16

Logistic growth model for change in biomass

Answer 16

(dB/dt) = rB(1 - (B/k))

• B is change in biomass
• r is growth rate
• might represent the dynamics of an unexploited fish stock

Question 17

Yield

Answer 17

-y variable that is added to the end of the logistic growth model for biomass

Question 18

What happens for a fishery to be in a steady state

Answer 18

-yield is in balance with the growth rate of the population

Y = rB(1 - (B/K))

Question 19

MSY

Answer 19

• maximum sustainable yield
• occurs at the max biomass (x axis) and max yield (y axis)
• biological reference point
• management criterion that is derived from biological considerations

Question 20

How do we define harvesting in terms of fishing effort

Answer 20

Y = qfB
q is catchability coefficient
f is fishing effort

Question 21

What is “q”

Answer 21

• catchability coefficient
• defined as the proportion of the total stock caught by 1 unit of effort
• can vary due to a number of factors so much be measured

Question 22

What is “f”

Answer 22

• fishing effort

- total amount of effort used and should always be standardized to a specific kind of effort

Question 23

CPUE

Answer 23

-catch per unit of effort

= Y/f

Question 24

Schaefer’s model

Answer 24

Y = af - bf^2

• yield on y axis, fishing effort on x
• parabolic curve, MSY occurs at the max
• this model allows us to estimate the parameters a and b

Question 25

when is a fish stock overfished

Answer 25

-when f is greater than or equal to (-a/b)