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Marine Ecology Progress Series

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MEPS 207:97-108 (2000)  -  doi:10.3354/meps207097

Population dynamics of the yellow clam Mesodesma mactroides: recruitment variability, density-dependence and stochastic processes

Mauricio Lima1,*, Alejandro Brazeiro2, Omar Defeo2,3

1Departamento de Ecología, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile
2UNDECIMAR, Facultad de Ciencias, Universidad de la República, Casilla 10773, 11400 Montevideo, Uruguay
3CINVESTAV IPN Unidad Mérida, 97310 Mérida, Yucatán, Mexico

ABSTRACT: Recruitment of benthic marine invertebrates varies greatly at different spatio-temporal scales. For instance, population dynamics of the yellow clam Mesodesma mactroides at Uruguay exhibit large temporal fluctuations, mainly associated with recruitment. We used data from an 8 yr long-term study to develop an age-structured model to show that density-dependent and density-independent forces acting together can jointly explain the population fluctuations in a sandy-beach bivalve population of the yellow clam Mesodesma mactroides. The pure density-dependent deterministic model parameterised with empirical values estimated during the 8 yr study predicted stable dynamics. The dynamics of the deterministic skeleton was markedly influenced by the addition of a relatively small amount of stochastic variability to fertility rates. The yellow clam population dynamics seem to be driven by the combined forces of density-dependent and density-independent factors operating together. A combination of (uncorrelated) stochasticity in reproductive rates and asymmetric intercohort interactions (density-dependent recruitment and density-dependent survival rates) seems to be the key process generating large variability in recruitment.

KEY WORDS: Mesodesma mactroides · Oscillations · Recruitment variability · Age-structured model · Marine invertebrates · Intercohort interactions

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