L14-Fisheries failures,MPA's

Question 1

What drives recruitment?

Answer 1

Total Egg Production (TEP) is what drives recruitment

Question 2

What is bi catch?

Answer 2

catching fish from other species

Question 3

What is Total Egg Production (TEP) modified by?

Answer 3

TEP is modified by the stock recruitment relationship

Question 4

What is recruitment?

Answer 4

TEP x SRR = recruitment

Question 5

What do managers assume?

Answer 5

linear relationship between fish size and body mass

size structure is irrelevant

Question 6

What does scaling describe?

Answer 6

how non-linear a function is

Question 7

How does reproductive output scale with size?

Answer 7

hyper allometric
reproductive output increases disproportionately with size
bigger fish produce more eggs with more energy per egg

Question 8

How does frequency of spawning change with size?

Answer 8

bigger fish spawn more

Question 9

What determines Total fecundity?

Answer 9

Batch fecundity x Spawning

Frequency

Question 10

Why does reproductive hyper allometry

matter to management?

Answer 10

• Fish reproduction scales hyperallometrically
• Biomass is not interchangeable
• Size structure is highly relevant

Question 11

Why is size structure being important such a problem?

Answer 11

bigger fish are fished preferentially

Question 12

how bigger proportion of pop would fish 3 years

and older will constitute Assuming a 20% harvest? How much of egg production assuming both isometry and hyper allometry?

Answer 12

just 0.4% of the population.
8% of egg production.
68% of
egg production.

Question 13

How often are fishing morality too high? by how much?

Answer 13

33 of world’s largest fisheries
2.4x too high on average
5x in some cases

Question 14

What proportion of fisheries models assume

isometry?

Answer 14

• 95%
• ~half are SPR models, half are MSY models
• Almost all MSY models just assume steepness values

Question 15

How much do we have to reduce catches?

Answer 15

30-40%

Question 16

What is happening to fish weight?

Answer 16

fish are getting smaller

evolving to mature at earlier age

Question 17

How much bigger are fish in mpa’s?

Answer 17

28% longer

twice as heavy

Question 18

What are the Concerns about MPAs as fisheries

management tools?

Answer 18

• They might not enhance replenishment
• They shift exploitation to elsewhere
• The carry no additional benefit beyond what good management would already provide

Question 19

How much more eggs are produced inside MPA?

Answer 19

140% more than twice number of eggs

Question 20

What is difference in reproductive output inside and outside mpa?

Answer 20

3 fold

and more fish

Question 21

total egg production in an outside mpa?

Answer 21

224 times higher

Question 22

How much do mpas enhance fishery?

Answer 22

two fold

Question 23

What are harvest slots

Answer 23

only target fish within a certain size range

if reproductive scaling above 1.5 can be effective

Question 24

Which of these assumtions from MAXIMUM SUSTAINABLE YIELD is liekly wrong?
• Stock spawner biomass 
• Growth 
• Natural mortality 
• Fishing mortality 
• Fishing selectivity 
• Steepness 
• Stock recruitment relationship

Answer 24

• Stock spawner biomass - Wrong
• Growth – Probably right
• Natural mortality – Probably wrong
• Fishing mortality – Probably wrong
• Fishing selectivity – Probably right enough
• Steepness – Almost certainly wrong
• Stock recruitment relationship - Almost certainly wrong

Question 25

What deo most fishery models assume about size?

Answer 25

Models assumed smaller fish are MORE

productive