11

Spatial Bioeconomic Model Evaluation ofBlue Ribbon Task Force Recommended Marine Protected Area Proposals for the North Coast

Study RegionPresentation to the MLPA Master Plan Science Advisory Team

January 13, 2011 • Teleconference and Webinar

Dr. Eric Bjorkstedt, Co-chair • MLPA Master Plan Science Advisory Team

Marine Life Protection Act Initiative

2

Model Description

• Models simulate population dynamics.• Model inputs include:

– Life history characteristics of modeled species– Larval dispersal predicted by ocean currents– Habitat data– Spatial fishing effort

• Models consider outcomes of three management scenarios:

– Conservative management– Maximum sustainable yield (MSY)-type

management– Unsuccessful management

33

Enhanced Compliance Alternative

• The North Coast Enhanced Compliance Alternative MPA Proposal (ECA) includes nearshore “ribbon MPAs” where a variety of uses are proposed to accommodate traditional tribal uses, paired with MPAs offshore where proposed uses are restricted to those at moderate high or high level of protection (LOP).

• Ribbon MPAs (which extend from shore to approximately 1,000 feet offshore) generally are narrower than a single model cell (1 square kilometer).

• To complete the modeling evaluation, it was necessary to assign the proposed uses associated with a nearshore ribbon MPA to the entire model cell, if the ribbon MPA overlapped the model cell.

• Because of this model constraint, the evaluation of the ECA is conservative; the ECA actually offers slightly more protection than indicated in the modeling evaluation.

4

Model Input: Larval Dispersal

Origin

Des

tinat

ion

Cape Blanco

Crescent City

Cape Mendocino

Pt Arena

Pt Reyes

Cap

e B

lanc

o

Pt

Rey

es

Probability of dispersal

Matrix for black rockfish (2000-2006 average)

Matrix: C. Edwards & P. Drake, UCSC

Cre

sce

nt C

ity

Cap

eM

endo

cino

Pt

Are

na

5

Model Description

• Six core species were modeled:– Black rockfish– Brown rockfish– Cabezon– Redtail surfperch– Red sea urchin– Red abalone

• Dungeness crab were also modeled but are presented separately because of characteristics of the fishery (only males are taken).

6

Model Outputs

• Conservation metrics– Spatial distribution of biomass– Total biomass (summed over study region,

weighted sum across species), relative to unfished biomass

• Economic metrics– Spatial distribution of fishery yield– Total fishery yield (summed over study region,

weighted sum across species), relative to maximum sustainable yield under Proposal 0

7

Biomass relative to unfished

Model Outputs: Biomass

• Map represents predicted spatial distribution of biomass.

• Outputs available for each:– Model species– Proposal – Management scenario

• Maps are posted online for:– Biomass– Fishery yield– Fishing effort– Larval production– Biomass for each MPA

(deletion analysis)

Example (RNCP): Black Rockfish Biomass

8

Model Outputs: Proposal Rankings

P0 RNCP ECA

0.1

0.12

0.14

0.16Unsuccessful Management

P0 RNCP ECA0.4

0.42

0.44MSY-type

Rel

ativ

e B

iom

ass

P0 RNCP ECA0.58

0.6

Conservative

P0 RNCP ECA

0.48

0.5

0.52Unsuccessful Management

P0 RNCP ECA

0.94

0.96

0.98

1

1.02MSY-type

Rel

ativ

e F

ishe

ry Y

ield

P0 RNCP ECA0.78

0.8

0.82

0.84 Conservative

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Model Results: Rankings in Context

Relative biomass

Rel

ativ

e fis

hery

yie

ld

conservation versus economic axis

- Choice along this axis is a matter of priorities, not science.

- Models can put the options in context

1010

Model Results: Rankings in Context

win-win axis

Relative biomassRel

ativ

e fis

hery

yie

ld

conservation versus economic axis

- Models can reveal where one proposal performs better than another for the species modeled.

- Differences are most apparent under assumption of unsuccessful management.

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Results: MSY-type Management*MSY is Maximum Sustainable Yield

P0

ECA

RNCP

Smaller grey dots indicate proposals from rounds 1,2 and 3

Legend

0.35 0.4 0.45 0.5

0.9

0.95

1

1.05

Relative Biomass

Rel

ativ

e F

ishe

ry Y

ield

12

0.5 0.55 0.6 0.65

0.75

0.8

0.85

0.9

Relative Biomass

Rel

ativ

e F

ishe

ry Y

ield

Results: Conservative Management

Smaller grey dots indicate proposals from rounds 1,2 and 3

P0

ECA

RNCP

Legend

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Results: Unsuccessful Management

Smaller grey dots indicate proposals from rounds 1,2 and 3

P0

ECA

RNCP

Legend

0.05 0.1 0.15 0.20.4

0.45

0.5

0.55

Relative Biomass

Rel

ativ

e F

ishe

ry Y

ield

14

0 0.2 0.4 0.6 0.8 1

0

0.2

0.4

0.6

0.8

1

Relative Biomass

Rel

ativ

e F

ishe

ry Y

ield

Results: Comparing Scenarios

conservative

MSY- type

unsuccessful

P0

ECA

RNCP

Legend

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Conclusions

• Deletion and larval production analyses suggest that the Skip Wollenberg-Ten Mile State Marine Reserve (SMR), Sea Lion Gulch SMR, and South Cape Mendocino SMR should be especially effective for most species in both ECA and RNCP.

• Vizcaino State Marine Conservation Area (SMCA), Reading Rock SMCA, and Pyramid Point SMCA are predicted to be more effective in ECA than in RNCP.

• No MPAs are predicted to decrease noticeably in effectiveness in ECA relative to RNCP.

• Genetic connectivity analysis suggests no difference between P0, RNCP, and ECA for long-dispersing species (e.g., black rockfish). For short-dispersing species (e.g., red abalone), ECA improves connectivity to Shelter Cove region from points south (relative to RNCP and P0).

All model outputs from this evaluation are posted on the MLPA website (www.dfg.ca.gov/mlpa)

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Conclusions

• The ECA consistently had highest relative biomass for all management assumptions.

• Proposal 0 (no action alternative) had highest relative fishery yield under MSY-type or conservative management.

• The ECA had highest economic value under unsuccessful management.

• The RNCP was intermediate between Proposal 0 and the ECA in all rankings.

• The evaluation of the ECA is conservative; the ECA actually offers slightly more protection than indicated in the modeling evaluation.

All model outputs from this evaluation are posted on the MLPA website (www.dfg.ca.gov/mlpa)