Scientia Marina, Vol 66, No 2 (2002)

Depth segregation phenomenon in Donax trunculus (Bivalvia: Donacidae) populations of the Algarve coast (southern Portugal)


https://doi.org/10.3989/scimar.2002.66n2111

Miguel B. Gaspar
Instituto de Investigação das Pescas e do Mar (IPIMAR), Centro Regional de Investigação Pesqueira do Sul (CRIPSul), Portugal

Luis M. Chícharo
Universidade do Algarve (UAlg), Faculdade de Ciências do Mar e do Ambiente (FCMA), Portugal

Paulo Vasconcelos
Instituto de Investigação das Pescas e do Mar (IPIMAR), Centro Regional de Investigação Pesqueira do Sul (CRIPSul), Portugal

Alexandra García
Instituto de Investigação das Pescas e do Mar (IPIMAR), Centro Regional de Investigação Pesqueira do Sul (CRIPSul), Portugal

Ana R. Santos
Universidade do Algarve (UAlg), Faculdade de Ciências do Mar e do Ambiente (FCMA), Portugal

Carlos C. Monteiro
Instituto de Investigação das Pescas e do Mar (IPIMAR), Centro Regional de Investigação Pesqueira do Sul (CRIPSul), Portugal

Abstract


A study was undertaken to evaluate the existence of depth segregation between size classes of Donax trunculus populations that occur along the Algarve coast (southern Portugal). Five collecting areas were sampled in the Ria Formosa barrier islands, namely in the Culatra, Barreta and Armona Islands, between March and June 1998. The study was based on size frequency distribution analysis and shell biometric relationships. The size frequency distribution showed the predominance of smaller individuals (< 25 mm) in the renewal area (0.5-1.0 m depth) and the prevalence of larger individuals (? 25 mm) at greater depths (4.0-6.0 m depth). The biometric study revealed the existence of significant differences in the type of growth between size classes in relation to depth distribution and burrowing activity. On the basis of these results, some specific management measures were proposed for this important bivalve fishery, taking into account the distinct fishing strategies and operations (manual and boat-operated dredging) performed at different depths.

Keywords


Bivalvia; Donacidae; Donax trunculus; wedge clam; depth segregation; relative growth; management measures; Portugal

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