A validated population-dynamics model for Scrobicularia plana (Mollusca, Bivalvia) in a south-western European estuary
P. M. Anastácio A C , T. Verdelhos B , J. C. Marques B and M. A. Pardal BA IMAR – Institute of Marine Research, c/o Department of Landscape, Environment and Planning, University of Évora, Rua Romão Ramalho, 59, 7000-671 Évora, Portugal.
B IMAR – Institute of Marine Research, c/o Department of Zoology, Faculty of Sciences and Technology, University of Coimbra, 3004-517 Coimbra, Portugal.
C Corresponding author. Email: anast@uevora.pt
Marine and Freshwater Research 60(5) 404-416 https://doi.org/10.1071/MF08127
Submitted: 19 April 2008 Accepted: 7 November 2008 Published: 25 May 2009
Abstract
During a recent intervention in the Mondego River estuary, Portugal, the existing connection between the north and the more eutrophic south arm was enlarged, a nutrient-enriched freshwater input was diverted to the north arm and the remaining seagrass patches were protected from human activity. System restoration did not involve disruption of the sediment and successfully reduced the eutrophic state of the estuary. This provided an excellent opportunity to test a population-dynamics model of a common European estuarine bivalve, Scrobicularia plana, (da Costa, 1778) before and after the intervention. The model simulated the number of individuals in three different sampling stations, before and after system restoration, and is regulated by water temperature, salinity and population density. Our analysis indicated that the occurrence of extreme values of the environmental variables has the strongest effect on the model response and possibly on the real system. The model was calibrated and validated with independent data sets and the model performance was highest under the conditions after the management. This corroborates the notion that system restoration was successful and indicates that the system became more predictable after management.
Additional keywords: bivalve, eutrophication, modelling, population dynamics, salinity, temperature.
Acknowledgements
The present study was partially supported by the research project DYNAMOD (POCTI/MGS/37431/2001), and WADI (FP6-INCO-CT-2005–015226). Tiago Verdelhos was supported by a Ph.D. grant from FCT – Fundação para a Ciência e Tecnologia (SFRH/BD/18812/2004). The authors are indebted to the anonymous reviewers and to the editor who provided very constructive comments and greatly contributed to improvement of the original document. Note that no permit is necessary for catching Scrobicularia plana in Portugal, although a permit is required for the capture of other bivalve species.
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