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The structure of fish communities in the Tagus Estuary, Portugal, and its role as a nursery for commercial fish species
M.J. Costa, A. Bruxelas

The Tagus is the largest estuary in Portugal (320 km2). Its fish community is composed of 44 species, with species diversity values varying between 0.85 and 2.237. Seven fish species use the estuary as a nursery area: Trisopterus luscus (Linnaeus, 1758), Ciliata mustela (Linnaeus, 1758), Dicentrarchus labrax (Linnaeus, 1758). Trigla lucerna Linnaeus, 1758, Platichthys flesus flesus (Linnaeus, 1758), Solea vulgaris vulgaris Quensel, 1806, and Solea senegalensis Kaup, 1858. While in the estuary, their growth rate is very high. This may be related to the availability of suitable food items. The brown shrimp Crangon crangon (Linnaeus, 1758) also uses the estuary as a nursery, and is a prefered prey of T. lucerna, D. labrax and C. mustela, and a secondary prey for S. vulgaris and P. flesus. The main food of these last two species are two polychaete species, Nereis diversicolor Miiller, 1852 and Lanice conchilega Pallas, 1778. Three shallow water stations near highly productive salt-marshes are the principal nursery areas for fishes. Young of the year D. labrax were caught first in nursery areas in May with a minimum standard length of 25 mm. The first catches of Solea vulgaris occurred in April, when juveniles had a standard length of 30 mm. The highest density was observed in May with 142.3 ind. 1000 m-1. Density values of Solea senegalensis were lower.

Keywords: estuaries, fishes, nursery areas, coastal fisheries.
Contents of this volume Sci. Mar. 53(2-3) : 561-566 Back PDF
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