JPR Advance Access originally published online on November 23, 2005
Journal of Plankton Research 2006 28(3):275-286; doi:10.1093/plankt/fbi104
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Environmental forcing and larval fish assemblage dynamics in the Lima River estuary (northwest Portugal)
1 Laboratory of Hydrobiology, Institute of Biomedical Sciences, University of Porto, No. 2, 4099-003 Porto, Portugal, 2 Centre of Marine and Environmental Research (CIMAR), Rua Dos Bragas 289, 4050-123 Porto, Portugal, 3 Rosenstiel School of Atmospheric and Marine Science, 4600 Rickenbacker Causeway, Miami, FL 33149-1098, USA and 4 Faculdade de Ciências da Universidade de Lisboa, Departamento de Biologia Animal, Campo Grande, 1749-016 Lisboa, Portugal
* Corresponding Author: ssramos{at}icbas.up.pt
Received August 12, 2005; accepted in principle October 25, 2005; accepted for publication November 14, 2005; published online November 23, 2005
Communicating editor: I.R. Jenkinson
This study investigated the potential control of selected abiotic parameters on an estuarine larval fish assemblage from the Lima River. Surveys were done fortnightly during spring tides, from April 2002 until April 2004, at 11 stations distributed along the estuary from the mouth to 7 km upstream. The surveys consisted of subsurface plankton tows of 5-min duration using a 1-m diameter, 500-µm mesh net and coupled with vertical profile measurements of temperature, salinity, dissolved oxygen, pH and turbidity. The Lima River estuary exhibited seasonal vertical stratification of salinity during the winter period, when salinity sharply increased with depth and a layer of fresh water was sometimes present at the surface. Temperature was always vertically stratified. Cooler water was typically found near the bottom of the water column, except during winter, when a thermal inversion occurred. A seasonal decrease in abundance and diversity of the larval assemblage was observed during winter, when fish larvae were almost absent from the plankton collections. Canonical correspondence analysis (CCA) results showed that the first axis represented a temporal gradient and the second axis represented a spatial gradient. Seasonal variations on temperature and precipitation were responsible for the temporal differences on the fish larval assemblages. This study reinforced the concept that interannual climate and hydrodynamic variations have a strong influence on estuarine ichthyoplankton and, consequently, on the recruitment of marine coastal fish populations.
This paper was presented at Plankton Symposium III, held at Figuera da Foz, Portugal between 17 and 20 March 2005, under the auspices of the University of Coimbra and the University of Aveiro, and coordinated by Mário Jorge Pereira and Ulisses M. Azeiteiro.