Recommended harvest strategy for�Aleutian Islands golden king crab�

Benjamin Daly1, M.S.M. Siddeek1, Mark Stichert1, Steven Martell2, Jie Zheng1�

Alaska Board of Fisheries Meeting�

Anchorage, AK�

March 9-12, 2019�

RC 3 1 Alaska Department of Fish and Game, 2 Sea State Inc.

1

State/Federal cooperative�management regime�

Federal process:

• NPFMC FMP: 10 BSAI crab stocks (including AIGKC)

• OFL (overfishing level): approximates MSY

• ABC (acceptable biological catch): below OFL to account for “the scientific uncertainty in the estimate of OFL and any other specified scientific uncertainty”

State process: harvest levels (TAC) and other management actions

• BOF Policy on King and Tanner Crab Resource Management, FMP, MSA national standards

• FMP Amendment 38: optimum yield ranges from 0 – <OFL�• Sum of all sources of fishing mortality <ABC

2

Overfishing Level (OFL)�Federal Government

25% buffer

Acceptable Biological Catch (ABC)�Federal Government

Below ABC

Total Allowable Catch (TAC)�State of Alaska

OFL: Level of fishing mortality that

jeopardizes the capacity of a stock to

produce the maximum sustained yield on

a continuing basis.

ABC: Level of annual catch that accounts

for scientific uncertainty and is set to

prevent the OFL from being exceeded.

In practice ABC limits mortality of ALL

male and female crabs regardless of size,

from all sources of fishery mortality (i.e.

retained catch, bycatch in directed and

non-directed crab fisheries, and

groundfish fisheries).

TAC: Annual catch target for the directed

fishery, set to prevent exceeding the ABC

for that stock. Limits legal sized males,

but must consider all sources of mortality

to ensure the ABC is not exceeded.

Considers model uncertainty and other

factors.

Ca

tch

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0

3

ATTU ..

200 MILE EXCLUSIVE ECONOMIC ZONE

BOUNDARY

REGISTRATION AREA 0 ALEUTIAN ISLANDS

..,,, PRIBILOF ISLANDS

....

CAPE SARICHEF 54 °36'N

•'!-~-• AKUT, N

ISLANDS OF FOUR MOUNTAIN; ~ UNALASKA

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G ,, AREA OF DETAIL

Western Aleutian Islands Eastern Aleutian Islands�

Current Fishery Management

• Size: 6.0 inches carapace width (152.4 mm)

• Sex: Male only

• Season: August 1 to April 30

• Managed east/west of 174° W longitude

• Gear: pots (longline)

• Harvest levels (total allowable catch; TAC) fixed in regulation

• Small fleet: 5 vessels

• Rationalized fishery

ADF&G Harvest strategy�The annual TAC is set by state regulation, 5 AAC 34.612 (Harvest Levels for Golden King Crab in Registration Area O), as approved by the BOF in March 2012:

(a) Until the Aleutian Islands golden king crab stock assessment model and a state regulatory harvest strategy are established, the harvest levels for the Registration Area O golden king crab fishery are as follows:

(1) east of 174° W long. (EAG): 3.31 million pounds; and

(2) west of 174° W long. (WAG): 2.98 million pounds;

(b) The department may modify the harvest levels based on the best scientific information available and considering the reliability of estimates and performance measures, sources of uncertainty as necessary to avoid overfishing, and any other factors necessary to be consistent with sustained yield principles.

*Prior to 2018, the word “reduce” was used

AIGKC stock assessment model�

• In development for nearly 10 years, accepted in 2017 by NPFMC for annual OFL and ABC determination

• AIGKC considered 1 stock, managed as 2 areas: east (EAG) and west (WAG) of 174° W long.

• OFL and ABC calculated for each management area separately, then combined for a single stock OFL and ABC

• Model-based abundance estimates now available • Abundance estimates allow TAC to be scaled to stock status:

better conservation, maximizes economic and social benefits

• No fishery-independent bottom trawl survey, no area-swept abundance estimates prior to model

7

Objective/purpose�

Objective: Develop a state harvest strategy that allows for abundance-based TAC calculations

How can we balance the tradeoff between conservation

and economic considerations?

• Conducted 30-year forecast simulations to evaluate how thirteen different harvest policies affect stock sustainability and productivity by comparing conservation and economic criteria

8

Forecast simulations�

What the analysis is:

• A tool used to estimate relative differences in population sustainability and productivity under different harvest policies

What the analysis is not:

• A crystal ball that tells us exactly what will happen over the next 30 years

9

Forecast simulations�• 2018 base model (scenario 18_0)

• Projected abundances for 30 years • Evaluated short term (1-8 years) and long term (1-30 years)�

results�

• 500 random replicates

• Estimated: • Mature males biomass (MMB)

• Mature male abundance (MMA)

• Legal male biomass (LMB)

• Overfishing level (OFL) Then calculated probabilities of: • Acceptable biological catch (ABC)

• Retained catch per unit effort (CPUE)

exceeding conservation • Total catch (TOTC)

thresholds, • Retained catch (RETC) meeting economic goals, etc.

• Number of annual recruits

10�

Evaluating State HCRs�Management criteria: 2-tiered approach

Conservation

1. Overfished: probability that MMB < MSST

2. Overfishing: probability that RETC + bycatch_mort > OFL (and ABC)

3. Probability that MMB < BMSY

Economic

1. Probability of fishery closure: MMB < 0.5MSST

2. Average retained catch (RETC)

3. Annual variability in retained catch

4. Probability that retained catch < historical mean catch

5. Probability that retained catch is within desired range • EAG: 4 mill lb ± 20%; WAG: 3 mill lb ± 20%

6. Mean CPUE

7. Probability that CPUE < historical mean CPUE

8. Relative fishing effort (RETC/CPUE)

9. Stock status: Probability that MMA < MMAAVE

• Indicator of where we are on the exploitation “ramp” 11

Harvest Control Rules�

Policy period for Exploitation rate on MMA Max Exploitation rate on MMA Exploitation rate cap on�MMAAVE MMA/MMAAVE%<100% MMA/MMAAVE%≥100% L abund�

0 1985-2017

1 1985-2017

2 1985-2017

3 1985-2017

4 1985-2017

5 1985-2017

6 1985-2017

7 1985-2017

8 1985-2017

9 1985-2017

10 1985-2017

11 1985-2017

12 1985-2017

13 1985-2017

0

MMA/MMAAVE X 0.10

MMA/MMAAVE X 0.125

MMA/MMAAVE X 0.15

MMA/MMAAVE X 0.20

MMA/MMAAVE X 0.30

MMA/MMAAVE X 0.10

MMA/MMAAVE X 0.125

MMA/MMAAVE X 0.15

MMA/MMAAVE X 0.20

MMA/MMAAVE X 0.30

MMA/MMAAVE X 0.175

MMA/MMAAVE X 0.225

EAG: 0.15, WAG: 0.23

0�

0.1�

0.125�

0.15�

0.2�

0.3�

0.1�

0.125�

0.15�

0.2�

0.3�

0.175�

0.225�

EAG: 0.15, WAG: 0.23�

0

0.25

0.25

0.25

0.25

0.25

0.3

0.3

0.3

0.3

0.3

0.25

0.25

none

12�

Exp

loit

ati

on

ra

te o

n m

atu

re m

ale

ab

un

da

nce

(M

MA

)�

Exploitation rate on mature male abundance (MMA)

30%

25%

20%

15%

10%

5%

0%

MMA/MMAAVE

30% ramp

22.5% ramp

20% ramp

17.5% ramp

15% ramp

12.5% ramp

10% ramp

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 110% 120% 130% 140% 150%�

* Includes 25% and 30% exploitation “caps” on legal male abundance 13

30

EAG MMB (model estimates)

EAG TAC

WAG MMB (model estimates)

WAG TAC

Historical TAC and MMB model estimates

• Population abundances fluctuate

• The TAC fixed in regulation

mil

lio

n l

bs

�

25

20

15

10

5�

0�

19

96

/97

19

97

/98

19

98

/99

19

99

/00

20

00

/01

20

01

/02

20

02

/03

20

03

/04

20

04

/05

20

05

/06

20

06

/07

20

07

/08

20

08

/09

20

09

/10

20

10

/11

20

11

/12

20

12

/13

20

13

/14

20

14

/15

20

15

/16

20

16

/17

20

17

/18

20

18

/19

14

Estimates of historical exploitation rates�

0.35

Exp

lota

tio

n r

ate

(G

HL/

MM

B)

usi

ng

20

18

mo

de

l e

stim

ate

s o

f M

MB

0.3

0.25

0.2

0.15

0.1

0.05

0

19

96

/97

19

97

/98

19

98

/99

19

99

/00

20

00

/01

20

01

/02

20

02

/03

20

03

/04

20

04

/05

20

05

/06

20

06

/07

20

07

/08

20

08

/09

20

09

/10

20

10

/11

20

11

/12

20

12

/13

20

13

/14

20

14

/15

20

15

/16

20

16

/17

20

17

/18

20

18

/19

EAG

EAG 10 yr mean

WAG

WAG 10 yr mean

23%

15%

• Exploitation rates have changed

over time within the EAG and WAG

• Exploitation rates have been

consistently higher in the WAG vs

the EAG

15

1

EAG�P

rob

ab

ilit

y�

Probability of exceeding OFL

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

Short term (yr 1-8)

Long term (yr 1-30)

Policy HR "ramp" Legal cap

0 0% 0%

1 10% 25%

2 12.5% 25%

3 15% 25%

4 20% 25%

5 30% 25%

6 10% 30%

7 12.5% 30%

8 15% 30%

9 20% 30%

10 30% 30%

11 17.5% 25%

12 22.5% 25%

13 15% fixed 0%

0 1 2 3 4 5 6 7 8 9 10 11 12 13�Policy�

0

16

WAG�P

rob

ab

ilit

y�

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0�

Probability of exceeding OFL�

Short term (yr 1-8)

Long term (yr 1-30)

Policy HR "ramp" Legal cap

0 0% 0%

1 10% 25%

2 12.5% 25%

3 15% 25%

4 20% 25%

5 30% 25%

6 10% 30%

7 12.5% 30%

8 15% 30%

9 20% 30%

10 30% 30%

11 17.5% 25%

12 22.5% 25%

13 23% fixed 0%

0 1 2 3 4 5 6 7 8 9 10 11 12 13�Policy�

17

EAG�P

rob

ab

ilit

y�

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0�

Probability of exceeding ABC�

Short term (yr 1-8)

Long term (yr 1-30)

Policy HR "ramp" Legal cap

0 0% 0%

1 10% 25%

2 12.5% 25%

3 15% 25%

4 20% 25%

5 30% 25%

6 10% 30%

7 12.5% 30%

8 15% 30%

9 20% 30%

10 30% 30%

11 17.5% 25%

12 22.5% 25%

13 15% fixed 0%

0 1 2 3 4 5 6 7 8 9 10 11 12 13�Policy�

18

WAG�P

rob

ab

ilit

y�

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0�

Probability of exceeding ABC�

Short term (yr 1-8)

Long term (yr 1-30)

Policy HR "ramp" Legal cap

0 0% 0%

1 10% 25%

2 12.5% 25%

3 15% 25%

4 20% 25%

5 30% 25%

6 10% 30%

7 12.5% 30%

8 15% 30%

9 20% 30%

10 30% 30%

11 17.5% 25%

12 22.5% 25%

13 23% fixed 0%

0 1 2 3 4 5 6 7 8 9 10 11 12 13 Policy 19

Policy HR "ramp" Legal cap

0 0% 0%

EAG�R

ET

C (

mil

lio

n l

bs)

�

5.5

5.0

4.5

4.0

3.5

3.0

2.5

0

Short term (yr 1-8)

Long term (yr 1-30)

7 12.5%

8 15%

9 20%

10 30%

11 17.5%

12 22.5%

13 15% fixed

1 10% 25%

2 12.5% 25%

3 15% 25%

4 20% 25%

Average Retained Catch 5 30% 25%

6 10% 30%

30%

30%

30%

30%

25%

25%

0%

1 2 3 4 5 6 7 8 9 10 11 12 13�Policy�

20�

EAG�

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

Re

tain

ed

ca

tch

(m

illio

n l

b)

25% L cap

30% L cap

Fixed 15%, No L cap

0% 5% 10% 15% 20% 25% 30% 35%�Exploitation rate on MMA�

21

Policy HR "ramp" Legal cap

0 0% 0%

1 10% 25%

2 12.5% 25% WAG 3 15% 25%

4 20% 25% Average Retained Catch� 5 30% 25%

RE

TC

(m

illio

n l

bs)

�

6 10% 30% 3.5

3.0

2.5

2.0

1.5

0 1 2 3 4 5 6 7 8 9 10 11 12 13

Short term (yr 1-8)

Long term (yr 1-30)

7 12.5% 30%

8 15% 30%

9 20% 30%

10 30% 30%

11 17.5% 25%

12 22.5% 25%

13 23% fixed 0%

Policy 22

WAG�

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5 R

eta

ine

d c

atc

h (

millio

n l

b)

25% L cap

30% L cap

Fixed 23%, No L cap

0% 5% 10% 15% 20% 25% 30% 35%

Exploitation rate on MMA� 23

5

EAG�R

eta

ine

d c

atc

h (

mil

l lb

)� 4

Legal cap

Policy 1

Policy 2

Policy 3

Policy 4

Policy 5

Policy 6

Policy 7

Policy 8

Policy 9

Policy 10

Policy 11

Policy 12

Policy 13

Relative fishing effort

Policy

0

1

2

3

4

5

6

7

8

9

10

11

12

13

HR "ramp"

0%

10%

12.5%

15%

20%

30%

10%

12.5%

15%

20%

30%

17.5%

22.5%

15% fixed

0% 3 25%

25%

25%

25%

25%

2 30%

30%

30%

30%

30%

25% 1 25%

0%

0.00 0.05 0.10 0.15 0.20 0.25

Relative effort (RETC/CPUE)�

0

24

WAG�R

eta

ine

d c

atc

h (

mil

l lb

)�

3.5

3

2.5 Legal cap

Relative fishing effort

Policy 1

Policy 2

Policy 3

Policy 4

Policy 5

Policy 6

Policy 7

Policy 8

Policy 9

Policy 10

Policy 11

Policy 12

Policy 13

Policy

0

1

2

3

4

5

6

7

8

9

10

11

12

13

HR "ramp"

0%

10%

12.5%

15%

20%

30%

10%

12.5%

15%

20%

30%

17.5%

22.5%

23% fixed

0%

25%

2 25%

25%

25%

25% 1.5 30%

30%

30% 1 30%

30%

25% 0.5

25%

0%

0.00 0.05 0.10 0.15 0.20 0.25

Relative effort (RETC/CPUE)�

0

25

Decision Matrix

Distill the conservation and economic risk metrics into a single decision table based

on policy ranks

Conservation Catch Catch Stability Metric Unit

Overfished Probability

Severely overfished Probability

Overfishing (OFL) Probability

Overfishing (ABC) Probability

Below BMSY Probability

Metric

Retained catch

Unit

Mill lb

Metric

Fishery closures

Annual catch var

Relative TAC (1)

Relative TAC (2)

CPUE (1)

Unit

Probability

Proportion

Probability

Probability -1

crab pot

CPUE (2)

Relative effort

Stock status

Probability -1

RETC CPUE

Probability

26

EAG: Decision Matrix�SHORT TERM (year 1-8)

Conservation Catch Catch Stability Policy Description HR "ramp" L cap

0 No fishing 0% 0%

1 10% ramp, 25% L cap 10% 25% 1 13 1

2 12.5% ramp, 25% L cap 12.5% 25% 3 11 2

3 15% ramp, 25% L cap 15% 25% 5 9 6

4 20% ramp, 25% L cap 20% 25% 9 5 9

5 30% ramp, 25% L cap 30% 25% 12 2 12

6 10% ramp, 30% L cap 10% 30% 2 12 3

7 12.5% ramp, 30% L cap 12.5% 30% 4 10 4

8 15% ramp, 30% L cap 15% 30% 6 8 7

9 20% ramp, 30% L cap 20% 30% 10 4 10

10 30% ramp, 30% L cap 30% 30% 13 1 13

11 17.5% ramp, 25% L cap 17.5% 25% 8 6 8

12 22.5% ramp, 25% L cap 22.5% 25% 11 3 11

13 15% fixed, No L cap 15% 0% 7 7 5

LONG TERM (year 1-30) Conservation Catch Catch Stability

Policy Description HR "ramp" L cap

0 No fishing 0% 0%

1 10% ramp, 25% L cap 10% 25% 1 13 1

2 12.5% ramp, 25% L cap 12.5% 25% 3 11 2

3 15% ramp, 25% L cap 15% 25% 5 9 6

4 20% ramp, 25% L cap 20% 25% 9 5 9

5 30% ramp, 25% L cap 30% 25% 12 2 12

6 10% ramp, 30% L cap 10% 30% 2 12 3

7 12.5% ramp, 30% L cap 12.5% 30% 4 10 5

8 15% ramp, 30% L cap 15% 30% 6 8 7

9 20% ramp, 30% L cap 20% 30% 10 4 10

10 30% ramp, 30% L cap 30% 30% 13 1 13

11 17.5% ramp, 25% L cap 17.5% 25% 8 6 8

12 22.5% ramp, 25% L cap 22.5% 25% 11 3 11

13 15% fixed, No L cap 15% 0% 7 7 4 27

WAG: Decision Matrix�SHORT TERM (year 1-8)

Conservation Catch Catch Stability Policy Description HR "ramp" L cap

0 No fishing 0% 0%

1 10% ramp, 25% L cap 10% 25% 1.5 13 1

2 12.5% ramp, 25% L cap 12.5% 25% 3.5 11 3.5

3 15% ramp, 25% L cap 15% 25% 5 9 5

4 20% ramp, 25% L cap 20% 25% 8 6 8

5 30% ramp, 25% L cap 30% 25% 12.5 1 13

6 10% ramp, 30% L cap 10% 30% 1.5 12 2

7 12.5% ramp, 30% L cap 12.5% 30% 3.5 10 3.5

8 15% ramp, 30% L cap 15% 30% 6 8 6

9 20% ramp, 30% L cap 20% 30% 9 5 9

10 30% ramp, 30% L cap 30% 30% 12.5 2 12

11 17.5% ramp, 25% L cap 17.5% 25% 7 7 7

12 22.5% ramp, 25% L cap 22.5% 25% 10 4 10.5

13 23% fixed, No L cap 23% 0% 11 3 10.5

LONG TERM (year 1-30) Conservation Catch Catch Stability

Policy Description HR "ramp" L cap

0 No fishing 0% 0%

1 10% ramp, 25% L cap 10% 25% 1.5 13 1

2 12.5% ramp, 25% L cap 12.5% 25% 3 11 3

3 15% ramp, 25% L cap 15% 25% 5 9 5

4 20% ramp, 25% L cap 20% 25% 8 6 6

5 30% ramp, 25% L cap 30% 25% 13 2 12

6 10% ramp, 30% L cap 10% 30% 1.5 12 2

7 12.5% ramp, 30% L cap 12.5% 30% 4 10 7

8 15% ramp, 30% L cap 15% 30% 6 8 8

9 20% ramp, 30% L cap 20% 30% 9 5 10

10 30% ramp, 30% L cap 30% 30% 12 1 13

11 17.5% ramp, 25% L cap 17.5% 25% 7 7 4

12 22.5% ramp, 25% L cap 22.5% 25% 10 4 11

13 23% fixed, No L cap 23% 0% 11 3 9 28

Summary: EAG • The 30% and 22.5% ramps (both L caps) are aggressive with

moderate/high probability of exceeding OFL • Moderate probability to being overfished (i.e., MMB<MSST) under

some recruitment scenarios

• The 17.5% and 20% ramps (25% L cap) and 15% fixed (No L cap) have moderate/high probability of exceeding ABC

• The 10% and 12.5% ramps are “safe” (low probability of exceeding conservation thresholds) but may not optimize yield

• The 15% ramp (with either the 25% or 30% legal cap) is likely the best trade-off between meeting conservation objectives and optimizing yield

• Moderate levels of conservation risk • Simulations predict TACs around 3.7 mill lbs with moderate annual

variability (~10-12%) without high increases in fishery effort relative to the 10% and 12.5% ramps

• Approximates historic exploitations rates

29

Summary: WAG�• The 30% and 22.5% ramps (both L caps) and the 23% fixed rate is

aggressive with moderate/high probability of exceeding OFL • Moderate probability to being overfished (i.e., MMB<MSST) under some

recruitment scenarios

• All policies with 15% ramps or higher have high probabilities of exceeding the ABC

• The 10% and 12.5% ramps are “safe” but may not optimize yield�• The 15%, 17.5%, and 20% ramps (with either legal cap) likely

the best trade-off between meeting conservation objectives and optimizing yield

• Increasing conservation risk within the 15%-20% range

• Predicted TACs are similar (2.6-2.7 mill lb)

• Annual catch variation is similar

• TACs will likely flirt with area-specific ABC • Simulation results are sensitive to how bycatch mortality is estimated

• Relative fishing effort has to increase dramatically for modest catch increase

30

Recommendation�

EAG: 15% ramp with a 25% legal cap

WAG: 15%, 17.5%, or 20% ramp with a 25% legal cap

Combined EAG policy 3 + WAG policy 4�

0

2

4

6

8

10

12

Milli

on

lb

s

OFL

ABC

RETC+Bycatch

RETC

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30�

Projection year 31

Thank you�

32