Xel-Há park for sustainable management

of Queen conch, Strombus gigas (Mollusca

Gastropoda) in the Mexican Caribbean

sea

Holistic program of Queen conch Strombus

gigas for sustainable management

CINVESTAVCINVESTAV--IPN Unidad MéridaIPN Unidad Mérida

LaboratorioLaboratorio biologíabiología y y cultivo de moluscos cultivo de moluscos

daldana@mda.cinvestav.mx

Dalila Aldana Aranda

Erick Baqueiro CárdenasManuel Sánchez y Ambar Pirrón

Cicata IPN Altamira

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S. gigas S. gigas is distributed in the Caribbean seais distributed in the Caribbean sea

This species represents one of the most valuable benthic resource in this region, exceeded only by the spiny lobster

� Landings in the Caribbean were estimated at 6,000 mt, with a value of $6,000,000 US, but Queen conch isnow an over exploited ressource.

1992 6 520 tons

1998 7 369

2000 4 598

2002 3 132

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S. gigas in the Caribbean has different International management measures for its conservation

1992: Queen conch was included in Appendix II under CITES (Convention on International Trade in Endangered Specie)

1994: Queen conch was included in the red list of International Convention for Nature conservation

2002: S. gigas was included in Annex II of SPAW (Specially Protected Areas and Wildlife in the Wider Caribbean region)

CITES is in charge of the international traffic, but each country is responsible for its protection and regulation. However, illegal catch and poaching is a common practice in most countries.Do n

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In Mexico, Queen conch has various management regulations

Yucatan State

• Due to over exploitation, in 1988 the fishery was closed

• Despite the total ban an illegal catch of 40 000 mt is estimated in Alacranes Reef which is a Marine Protected Area

The resource is overfished

1981

1982

1983

1984

1985

1986

1987

1988

1989

0

500

1000

1500

2000

mt

years

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• The annual quota is fished in 20 days

• The illegal catch in these MPA is estimated at 60 mt

• Temporal Ban from May to October

• Minimum catch size : 20 cm

• Annual Quota is 42 mt

Quintana Roo,State 19

8119

8219

8319

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9519

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0

200

400

600

800

1000

1200

1400

mt

years

Queen conch regulation includes

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Objective

In order to know the population parameters of

S. gigas in a Marine Protected Area without any

type of extraction, S. gigas population of Xel-Há

Park was studied by catch and recapture method

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Xel-Há Park is situated in the Mexican Caribbean sea

Latitude and longitude:

25 30º E and 60’ 65o W.

Quintana Roo

XEL Há

Yucatan Peninsule

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Sampling and MeasuresShell lenght

Lip thikness

• Sampling took place from November 2001 to June 2005

• Each Conch was measured in length and lip thickness

• Size frequency histograms were used to analyze the population structure

L∞ and k were estimated according to the methods of Von Bertalanffy

(FISAT program,FAO-ICLAMAR Stock Assessment Tools)

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Results

Length frequency distribution for the total population

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Whole population

0

50

100

150

200

250

300

32.5

47.5

62.5

77.5

92.5

108

123

138

153

168

183

198

213

228

243

258

273

mm

Fre

quency

Without lip

0

10

20

30

40

32.5

47.5

62.5

77.5

92.5

108

123

138

153

168

183

198

213

228

243

258

273

mm

Fre

quency

Length frequency

Total shell length

distribution for:

• Whole population

• Conchs without lip

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Lip thickness frequency distribution

Thickness (mm)Thickness (mm) Thickness (mm)

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Lip thickness

010

2030

4050

6070

80

1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46

mm

Fre

quency

Lip thickness frequency

A complex structure of

several cohorts was

observed

Several year classes are

combined, giving

opportunity for an

independence size

structure analysis of

conchs with lip

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Von Bertalanffy growth parameters

for shell length

0.8-1.8-1.4T0

1.271.191.55Z

00.5*0.8*C

00.50.3Wp

0.40.070.03K

299330251Loo

Total

population

Conchs

with lip

Conchs

without

lip

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http://www.nhm.ac.uk/palaeontology/i&p/gastroclass/gastroclass.htm

0.03K

251 mmLoo

Conchs

without lip 4 years

Von Bertalanffy growth parameters

for shell length without lip

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http://www.nhm.ac.uk/palaeontology/i&p/gastroclass/gastroclass.htm

0.07K

330Loo

Conchs

with lip13 years

Von Bertalanffy growth parameters

for shell length with lip

4 yearsDo n

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Recruitment from shell length

From size frequency distribution for the whole population

From catch recapture data for the whole population

*

*

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Von Bertalanffy growth parameters for lipthickness

-1.8-1.4T0

0.29*0.48*Z

0.50.8C

0.50.3Wp

0.190.17K

52.0447.78Loo

F. D.C. R. • C.R. from catch recapture data.

• F.D. from size frequency distribution.

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Discussion

• The population of queen conchs at Xel Ha park is mainly composed of sub adults and adult conchs

• Size structure of adult (with lip) and subadult (without lip) conchs is quite similar

• Catch recapture data and size frequency distribution estimates give similar results

• Lip thickness is a good measurement for the estimate of age for conchs with lip which represent the reproductive stock

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Discussion

• According to Delgado et al. (2004) Queen conch populations appear as more dependent on local retention of larvae than on recruitment from upstream sources.

• According to Glazer et al. (2004) MPAs can be an alternative for the protection of reproductive stocks, especially for non-migratory species with a long life span as the Queen conch, which recruitment seems to depend on the size of the reproductive stock.

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Conclusions

• Xel Ha park is a closed area with restricted communication to the sea. However, there is a significant recruitment that sustains a healthy population

• MPAs would contribute to preserve the reproductive stocks:

� as a source of larvae for recruitment

� as a protected area for growth

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