Molluscs traditional exploitation in Senegal: Anadara senilis L. (1758)

Biological potentialities and risks

Dr Alvares G. F. BENGAGeography DepartmentUniversity of Ziguinchor

Senegal

ICSR' 08ICSR' 08Double Tree Guest SuitsDouble Tree Guest Suits

CharlestonCharleston 19 to 22 November 2008 19 to 22 November 2008

Introduction (1)

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Senegal: 708 km of coast, A country of strong maritime

tradition In addition to fish, shellfish and the

molluscs are also exploitated, in particular in the Saloum delta and Casamance river

Anadara senilis as a key specie for the research

Introduction (2)

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Introduction (3)• The overexploitation indices

pointed out in the principal production areas have led to programs of conservation based primarily on the biological rest

• These programs were applied on the basis of overexploitation indices, but not valuable data on the available and catched potential, and often, give lukewarm results at the end.

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Methodology

Largest area of production, which is the Saloum Delta, combined of research methods to the sites of Niodior and Bettenty:* A follow-up, * Inventory and Biometric processes on the * Inventory and Biometric processes on the mudflats to have indicators of the mudflats to have indicators of the exploitation.exploitation.

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Objectives • To appreciate the available

and the level stock of Anadara senilis collection,

• To have arguments to justify or discuss the suitability of the biological rest, which virtues are extolled by local NGOs and supported by many researchers

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Results (1)

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***** 5 indicators of the socio-economic follow-up were identified: • An activity led by a natural and strategic regulator - the monthly frequency of field trip-Lengh of field trips-Average catched biomass-The selective collecting area-Declared manpower

-***Inventories and Biometric data- Permanent reproduction,- Permanent reproduction,- A reverse gradient biomass/ density and which rests a dilemma- A reverse gradient biomass/ density and which rests a dilemma- The rough available biomass is largely higher than the - The rough available biomass is largely higher than the catched levelcatched level

Results (2)

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Results (3) • Difficulties to postulate the risk of

ark’s exhaustion and, consequently, the institution of biological rest of a mudflat because of an selective collection.- The collection is still selective and manual- The statutory system for accessing the resource and the rights of access to the mudflat remain jealously protected- Commercial size still strictly respected - Anadara senilis is a specie of high productivity and very tolerant

• the existence of strategic factors controlling the exploitation, in order to create a natural biological rest

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Discussions (1)

• in Senegal, the “overexploi- tation” evoked on this resource, at local scale, is not proven • Consequently, “overexploitation” indices,

admitted by all, can be the result of a high number of collectors ?

• Biological rest, the single solution to restore the stocks and to bring it back to suitainable levels?

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Discussion (2)

++The biological rest test doesn’t present less considerable interest as it permits to

explore a scenario of management

++The biological rest can be an additional

complex factor .

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Conclusion

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• the potential of reproduction, • the level of predation and natural mortality, • The durable exploitation threshold of the resource or

Maximal Sustainable Yield) is still unknown • and other factors inherent to the resource as

well as the repercussion of the ecological conditions seem to be as many research themes to investigate.

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