Why SPAs (Marine Reserves) are Necessary for the Sustainable Management of Queen Conch in the Florida Keys (and elsewhere)

Bob Glazer and Gabriel DelgadoFlorida Fish and Wildlife Conservation Commission Fish and Wildlife Research Institute Marathon, FL USA

The Questions

How can Conch Biology Guide us to Develop Sustainable Management Approaches?

(traditional fishery methods, ecosystem-based methods such as MFRs)

Does Existing Zoning within FKNMS Protect Conch should a limited recreational fishery be opened?

The Fishery has Been Closed Since 1986

The First Order of Business: Where do the Larvae Come from?

Plankton Surveys

In Concert With:

Drift Vials

Satellite Imagery

HydrodynamicsDrifters

Patterns in population recovery

Pourtales Gyre

Florida Current

Spin-

Off Ed

dies

Tortugas Gyre

Loop Current

The Oft-Cited Synthetic Model

Florida Current Sheer

Florida Keys Entrainment Zone

Delgado and Glazer, 2005

Focus of Surveys on Reproductive Behavior

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FloridaBay

Kilometers120600

Gulf of Mexico

*

Nearshore AggregationHawk Channel

Offshore Aggregation

Everglades National

Park

*

N

EW

S

Conch Distribution

Surveying the AggregationsDensity of AdultsDensity of Spawning Conch

Density (adult conch hectare-1)

0 500 1000 1500 2000 2500 3000 3500Mat

ing

Den

sity

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N=286

DEPENSATION AT LOW DENSITIES

0-200

200-4

0040

0-600

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ing

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Density (adult conch hectare-1)

42 49 65 1957 25 28

N= 286

Density (adult conch m-1)

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sity

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0-200

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Density (adult conch hectare-1)

42 49 65 1957 25

N= 286

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Density (adult conch m-1)

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ing

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sity

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DENSITY DEPENDENT RESPONSE

0-200

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Density (adult conch hectare-1)

42 49 65 1957 25 28

N= 286Adult Conch Density (adults • hectare-1)

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ing

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sity

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Equilibrium (unfished)

Density (adult conch hectare-1)

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atin

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N=286

Queen conch in sparse aggregationsCan’t mate due to strong depensation

But when densities per sectorExceed 200 per hectare

The conch resume normal relations

Results of the Surveys

Densities of Queen Conch Aggregations

> 200 adults per ha> 800 adults per ha

< 200 adults per ha

Fished Unfished

…Slippery Slope to Extinction

Density (adult conch hectare-1) 12

00+

1000

-1200

800-1

000

600-8

0040

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200-4

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0-200

Pro

babi

lty o

f Mat

ing

0.0

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unfished

…Slippery Slope to Extinction

Density (adult conch hectare-1) 12

00+

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-1200

800-1

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600-8

0040

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Pro

babi

lty o

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fished

To Recap…

Conch must achieve at least 200 conch/ha for any reproduction to occur

An unfished population can be expected to approach or exceed 800 conch/ha

There is a bonus relative to per capita reproductive encounters for densities between 200 conch/ha and 800 conch/ha

Conclusions – Question 1

It’s All About Density – Management of Conch Must Focus on Density

Relatively Sedentary, Dioecious Species (e.g., Urchins, Abalone) also Likely Benefit Greatly from Reserves

therefore…No-Take Marine Fishery Reserves are Absolutely Essential for Sustainable Management of Conch in Florida ANDElsewhere

- Any open fishery will likely reduce Most Adult Aggregation Densities to < 200 per hectare

Question 2: Guided by These Principles, Does Existing Zoning in FKNMS Protect

Conch Within a Hypothetical Scenario of a Recreational Fishery?

Western Sambo Ecological Reserve

Eastern Sambo Research Only

Eastern Dry Rocks SPA

Alligator SPAConch SPASombrero SPA

Looe Key SPA

Elbow SPAGrecian SPAFrench SPA

Molasses SPA

Are the SPAs as Currently Designed (a) Large Enough and, (b) Correctly Placed if a Limited Recreational Conch Fishery Opens?

Conclusions – Question 2

The SPAs as Currently Designed ARE Large Enough

…but, in many cases, the SPAs are Not Well-Placed for Florida’s Conch Conservation so They Would Need to be Resized or Adjusted

Caveat: …if a recreational fishery opens

Many Aggregations are Not in Close Association with SPAs

The many volunteers and employees who worked on this project over the last 15 years and

• Florida Fish and Wildlife Conservation Commission Fish and Wildlife Research Institute

• The University of Florida Institute of Food and Agricultural Sciences Environmental Statistics

• NOAA• The Nature Conservancy of the Florida Keys.

Thanks to

Density (adult conch m-1)

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ing

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N=286 The Problems with Spawning Potential Ratio (SPR)*

*Reproductive Output Fished /Reproductive Output Unfished

Q1. What if We Used a Traditional Fisheries Approach?

SPR=0.5

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Density (adult conch m-1)

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NO

REPR

ODUC

TION

Adult Conch Density (adults • hectare-1) Depensation

Density (adult conch m-1)

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NO

REPR

ODUC

TION

Adult Conch Density (adults • hectare-1)

Adult Conch Density (adults • hectare-1)

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ing

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Representative of an Unfished Population

Year1993 1995 1997 1999 2001 2003 2005 2007 2009

% o

f Agg

rega

tions

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% <200 (pre-recovery)%Med (Recovering)%High (Recovered)

18 19 12 16 16 12 13 13 19 31 24 23 27 10 18N=

Extending the Concept

Bertelsen et al. 2001

one, 61 cm 12.5 kg female produced as many eggs as 212females 42 cm 1.12kg!!!

Red Snapper (Lutjanus campechanus )

Grimes 1987