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RESEARCH ARTICLE
Contents Vol 61(4)

Effects of freshwater flow on the fish assemblage of the Mondego estuary (Portugal): comparison between drought and non-drought years

Joana Baptista A D , Filipe Martinho A , Marina Dolbeth A , Ivan Viegas A , Henrique Cabral B and Miguel Pardal A C
+ Author Affiliations
- Author Affiliations

A IMAR–CMA, Marine and Environmental Research Centre, Department of Life Sciences, University of Coimbra, Apartado 3046, 3001-401 Coimbra Portugal.

B Centro de Oceanografia, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal.

C CEF – Center of Functional Ecology, Department of Life Sciences, University of Coimbra, Apartado 3046, 3001-401 Coimbra Portugal.

D Corresponding author. Email: joana.baptista@student.biologia.uc.pt

Marine and Freshwater Research 61(4) 490-501 https://doi.org/10.1071/MF09174
Submitted: 9 July 2009  Accepted: 13 November 2009   Published: 27 April 2010

Abstract

Warming of the planet is indisputable and will lead to more frequent extreme events, such as droughts. From June 2003 to March 2008, the effects of variations in river flow, associated with drought conditions, were studied in the fish assemblage of the Mondego estuary, Portugal. Over this time, two distinct hydrological periods were identified: non-drought years and drought years, with consistent changes in the fish assemblages. In the drought years, salinity increased inside the estuary, displacing the estuarine brackish habitats to more upstream areas. During this period, new marine adventitious species were found mainly in the most downstream areas, while the freshwater species disappeared from the Mondego estuary catchment area. For the marine estuarine-dependent species that use estuaries as nursery areas, a decrease in abundance was observed during the drought years, owing to the decrease in freshwater flow and reduced river plume to the coastal area. In non-drought years, there were higher densities of most species and the more important species of the fish community. Our work shows that extreme events such as droughts, related to climatic changes, influenced the structure and composition of the Mondego estuary fish assemblages, and should be further considered when undertaking management plans for transitional waters.

Additional keywords: drought period, Mondego estuary, precipitation, runoff, salinity.


Acknowledgements

The authors wish to thank colleagues that assisted in the field and laboratory work. This work was supported by Instituto de Investigação Interdisciplinar-Universidade de Coimbra (III-UC) through the Research project ‘Os recursos pesqueiros no âmbito da política Europeia de desenvolvimento sustentável: uma abordagem interdisciplinar para o caso do robalo (Dicentrarchus labrax)’ (III/AMB/4/2005). The paper benefited from the comments and suggestions of Dr Alan Whitfield, three other anonymous referees and the editor Dr Andrew Boulton.


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