wf4133 fisheries science - github pagesf msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate yield...
TRANSCRIPT
![Page 1: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/1.jpg)
WF4133‐Fisheries Science
Module 3: Harvesting biomassClass 13
![Page 2: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/2.jpg)
Housekeeping
• Now is the time to be looking for summer jobs!– State websites– USA jobs– Fisheries.org– Texas A&M
• No lab today!
![Page 3: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/3.jpg)
HARVESTING BIOMASS CONTINUEDHow do we deal with the issues assuming equilibrium?
![Page 4: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/4.jpg)
Fmsy
0.0 0.2 0.4 0.6 0.8 1.0
0
50
100
150
hrate
Yie
ld
Fishing mortality rate
Fmsy
Fishing mortality rate that maximizes sustained yield
![Page 5: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/5.jpg)
Biological overfishing!
0.0 0.2 0.4 0.6 0.8 1.0
0
50
100
150
hrate
Yie
ld
Fishing mortality rate
Fmsy
Yield DecreasesWith More Effort
![Page 6: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/6.jpg)
Epitaph for MSY
![Page 7: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/7.jpg)
Solution for equilibrium = F0.1The use of F0.1 has emerged as a useful “rule of thumb” for managing fisheries, but according to Hilborn and Walters (1992) this is an arbitrary, ad hoc strategy with no theoretical basis.
OK, so what is it exactly?
![Page 8: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/8.jpg)
Shifting MSY to the left…
0.0 0.2 0.4 0.6 0.8 1.0
0
50
100
150
hrate
Yie
ld
Fishing mortality rate
Shift Fmsy to the left… reduce it
Fmsy
![Page 9: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/9.jpg)
How do we figure out F0.11. Find slope at origin2. Plot line with 10%
of this slope3. Find tangent of
curve at this slope
![Page 10: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/10.jpg)
Slope at origin
0.0 0.2 0.4 0.6 0.8 1.0
0
50
100
150
Fishing mortality
Yie
ld
![Page 11: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/11.jpg)
10% of slope at origin
0.0 0.2 0.4 0.6 0.8 1.0
0
50
100
150
Fishing mortality
Yie
ld
![Page 12: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/12.jpg)
10% of slope at origin
0.0 0.2 0.4 0.6 0.8 1.0
0
50
100
150
Fishing mortality
Yie
ld
![Page 13: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/13.jpg)
F0.1
0.0 0.2 0.4 0.6 0.8 1.0
0
50
100
150
Fishing mortality
Yie
ld F0.1 = 0.28
FMSY = 0.3
F0.1
![Page 14: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/14.jpg)
Continuous harvest assumption
Suppose harvest does not occur continuously…Is this realistic?Examples?
![Page 15: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/15.jpg)
Solution for equilibrium = F0.1The use of F0.1 has emerged as a useful “rule of thumb” for managing fisheries, but according to Hilborn and Walters (1992) this is an arbitrary, ad hoc strategy with no theoretical basis.
![Page 16: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/16.jpg)
Continuous harvest
http://www.mdwfp.com/media/218652/creel_limits_pt._3_chaper_1.pdf
![Page 17: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/17.jpg)
Continuous harvest?
Colvin, M.E., Pierce, C.L., Stewart, T.W., 2012. Semidiscretebiomass dynamic modeling: an improved approach for assessing
fish stock responses to pulsed harvest events. Canadian Journal of Fisheries and Aquatic Sciences 69, 1710‐1721.
![Page 18: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/18.jpg)
Traditional biomass models
• Assumes harvest occurs continuously
• Biomass models guide stock management
• Pulsed harvest?
0 2 4 6 8 10
0
50
100
150
200
250
300
Years
Biom
ass
Continuous harvest
Does assuming continuous harvest make a difference?
![Page 19: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/19.jpg)
Pulsed harvest & biomass dynamics
0 2 4 6 8 10
0
50
100
150
200
250
300
Years
Biom
ass
A Pulsed Harvest System
Pulsed biomass removal
Development of Semi‐Discrete Biomass Dynamics Models (BDMs)
![Page 20: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/20.jpg)
Semi‐discrete models• Hybrid class of models that allow pulsed events in continuous time
• Continuous processes‐ intrinsic growth rate
• Pulsed harvest
0 2 4 6 8 10
0
50
100
150
200
250
300
Years
Biom
ass
Pulsed harvest
![Page 21: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/21.jpg)
0 2 4 6 8 10
0
50
100
150
200
250
300
Years
Biom
ass
Can biomass dynamics models be improved by accounting for pulsed harvests? YES
0 2 4 6 8 10
Years
Pulsed harvestContinuous harvest
Better!
![Page 22: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/22.jpg)
0.00 0.05 0.10 0.15 0.20 0.25 0.30
0
5
10
15
20
25 A: Schaefer
Continuous FMSYSemi-discrete FMSY
ContinousSemi-discrete
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
0
5
10
15
20
25
30 B: Fox
Continuous FMSYSemi-discrete FMSY
0.00 0.05 0.10 0.15 0.20 0.25 0.30
0
5
10
15
20 C: Pella-Tomlinson
Continuous FMSYSemi-discrete FMSY
Equ
ilbriu
m y
ield
(kg
ha1
)
Fishing mortality (kg ha1yr1)
Equilibrium yields
Assuming continuous harvest over estimates MSY!
![Page 23: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/23.jpg)
0
50
100
150
200
250
Biom
ass
(kg/
ha) A: Biomass
468
10121416
Cat
ch p
er u
nit
effo
rt (k
g/tra
wl)
B: CPUE
2007 2008 2009 2010 2011
0
5
10
1520
25
Biom
ass
(kg/
ha)
Year
C: Weekly harvest April-JuneOctober-November
Applying this to carp
![Page 24: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/24.jpg)
Carp biomass dynamics model
Fit to data by maximum likelihood to estimate r & q, given B, I, and C
![Page 25: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/25.jpg)
Estimating standing biomass
Mark Weigh
Recapture
![Page 26: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/26.jpg)
Trawling to index biomass (CPUE) A: 2007
B: 2008
C: 2009
D: 2010
N
Seine locationTraw l location
![Page 27: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/27.jpg)
Tracking carp biomass harvested
When & how much biomass is harvested
![Page 28: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/28.jpg)
0
50
100
150
200
250Bi
omas
s (k
g/ha
) A: Biomass
468
10121416
Cat
ch p
er u
nit
effo
rt (k
g/tra
wl)
B: CPUE
2007 2008 2009 2010 2011
0
5
10
1520
25
Biom
ass
(kg/
ha)
Year
C: Weekly harvest April-JuneOctober-November
![Page 29: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/29.jpg)
100
150
200
250
Bio
mas
s (k
g/ha
)
2007 2008 2009 2010 2011
4
6
8
10
12
14
16
Cat
ch p
er u
nit
effo
rt (C
PU
E: k
g/tra
wl)
Model predicted biomass
Model predicted CPUE
Fittedmodel
![Page 30: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/30.jpg)
The big picture
• Global fisheries estimated to be worth $91.2 billion according to United Nations– 82 billion for saltwater– 10 billion for freshwater– In the round…
• Managing fisheries is serious economic business
• Lots of stakeholders…
![Page 31: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/31.jpg)
Not just about yield
• MSY is tough to attain• Really not interested in catching fish for the sake of catching fish
• Interested in $$$• Linking yield to money• Lets look at Spring Chinook salmon
![Page 32: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/32.jpg)
Spring Chinook life historyRedds & eggs Parr (0+)Hatch Fry (0+)
Smolt (1)
Mini jack (2)
Jack (3)
Adult (4)
Adult (5)
Adult (6)
![Page 33: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/33.jpg)
Willamette Basin Spring Chinook
![Page 34: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/34.jpg)
Fish return ~ February
Pacific Ocean
![Page 35: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/35.jpg)
Commercial fisheries & profits
![Page 36: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/36.jpg)
Spring Chinook Salmon
• Average 25 pounds• 16 to 25 USD per pound in the round• 400 to 625 USD per fish!
– 1000 fish= 40 to 62.5K USD– 10,000 fish = 400 to 625K USD
![Page 37: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/37.jpg)
Why so expensive?
• Life history• Return to freshwater early!
![Page 38: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/38.jpg)
Biomass & harvest dynamics
tt
biomass
economic
K BiomassdBiomass r F Biomassdt K
dYield F Biomassdt
dYield F Biomass Landing pricedt
![Page 39: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/39.jpg)
MSY & economic yield
Link yields to profits• Graham Schaefer
r=0.3K=10,000B0=9,000Landing price=4 usd/kg
![Page 40: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/40.jpg)
Sustained yield
0 100 200 300 400
0
100
200
300
400
500
600
Effort (hours)
Yie
ld (t
ons)
![Page 41: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/41.jpg)
Economic yield
0 100 200 300 400
0.0
0.5
1.0
1.5
2.0
Effort
Pro
fit (x
1000
)
Same as MSY but for profit
![Page 42: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/42.jpg)
No free lunch
• Harvest of fish requires effort!• Effort cost something… money, person hours
![Page 43: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/43.jpg)
Fisheries & effort
![Page 44: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/44.jpg)
Incorporating effort
![Page 45: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/45.jpg)
Effort
Gear Effort (days)
Totalcatch
Catch per effort
Gill nets 55 6600 120
Need to link effort and yieldExample if I fish for 4 hours how much fish will I catch?
![Page 46: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/46.jpg)
Catchability
6600 55catchability Biomass
catchCatch ef
abilityfo
Biomassrt
Just need to know biomass….Or catchability
![Page 47: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/47.jpg)
Estimating biomass & catchability
• Mark recapture• Calibrated fishery independent surveys• Catchability is much more difficult
– Function of biomass–Need catch, biomass, and effort
![Page 48: WF4133 Fisheries Science - GitHub PagesF msy 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 hrate Yield Fishing mortality rate F msy Fishing mortality rate that maximizes sustained yield](https://reader036.vdocument.in/reader036/viewer/2022071410/61045af0c137c04f377634ae/html5/thumbnails/48.jpg)
Biomass & harvest dynamics
tt
biomasst
economict
K BiomassdBiomass r catchability Biomassdt K
dYield ca
eff
tchability Biomassdt
dYield catchability Biomass Landing price
ort
effort
effortdt