L13-fisheries II, core principles, key terms,biological reference points

Question 1

What is recruitment dependent on?Why?

Answer 1

• Recruitment is density-dependent, competition is strong

Question 2

What is a TAC?

Answer 2

total allowible catch

Question 3

What is the Low data approach?

Answer 3

Yield per recruit

simplest model of fishery manergement

useful when you don’t have much information

just looks at fihing mortality and yield per recruit

looks logarithmic

Question 4

Can you fish above maximum sustanible yield ?

Answer 4

yes and fish won’t go extinct but you will get less fish?

Question 5

What are the Biological reference points?

Answer 5

B = Sustainable Biomass F = Fishing mortality

Question 6

What is Spawner Stock Biomass?

Answer 6

biomass of reproducing fish

Question 7

What is the ideal Biological reference points?

Answer 7

eggs produced?

Question 8

what does f greater than F threshold mean?

Answer 8

stock is being overfished

Question 9

What is F5?

Answer 9

fish mortality rat that reduces the spawning stock per recruit to a given percentage?

Question 10

What fish are caught more often?

Answer 10

larger, older fish

Question 11

What is stock recruitment relationship?

Answer 11

defines the density dependence relationships

two models

beveton-holt model

ricker model

Question 12

What is steepness?

Answer 12

is an estimate of density dependence

low values mean little density dependence

high values mean high density dependece(mean pop can be taken to low level and

Question 13

What does steepness of 1 mean?

Answer 13

if there is some fraction of the stock left, recruitment is 100% equivalent to a virgin stock

Question 14

What does a Steepness >0.3 <1 mean?

Answer 14

Density dependence but imperfect compensation. 0.3 would imply no density dependence

Question 15

What doe you need to calcualte MAXIMUM SUSTAINABLE YIELD?

Answer 15

• Stock spawner biomass
• Growth
• Natural mortality
• Fishing mortality
• Fishing selectivity
• Steepness
• Stock recruitment relationship

Question 16

What do you need to know YOU CAN CALCULATE SPAWNING POTENTIAL RATIO?

Answer 16

• Stock spawner biomass
• Growth
• Natural mortality
• Fishing mortality
• Fishing selectivity

assume you can remove on third and pop will be fine

Question 17

What do you need to know for YOU CAN CALCULATE YIELD PER RECRUIT?

Answer 17

• Growth
• Natural mortality
• Fishing mortality

typically not sustanible

common in low inforamtion fishiereis

Question 18

What does Maximum sustainable yield (MSY) have?

Answer 18

has reproduction and explicit density dependence

Question 19

What does Spawning potential ratio (SPR) have?

Answer 19

has reproduction and some (implicit) density dependence

Question 20

What does Yield per recruit (YPR) have?

Answer 20

has no reproduction or density dependence (most common in Indian Ocean)

Question 21

What is comon problem in fisheries mangement?

Answer 21

Catch > TAC

Question 22

What is the general trend in fishieres?

Answer 22

more and more over exploited

30% fishieres are not sustanible

Question 23

reasons for overfishing?

Answer 23

• Excess landings
• Illegal fishing
• Bycatch and Discards
• Political overreach-politations set catch above scentific
• Incorrect models???

Question 24

How well are Australian fishieres manged?

Answer 24

horrible

much worse than US

only 1% of stock is assesed

Question 25

What is the Austrailian context?

Answer 25

• Fisheries management is minimal in Australia
• Assessment is rudimentary and limited
• Catches are often lower than TAC
• Recreational fishing is responsible for ~50% of coastal catch
• Very poorly regulated
• MPAs are poorly enforced or reversed.