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|Title: ||Comparative ecology of the European eel, Anguilla anguilla (L., 1758), in a large Iberian river|
|Authors: ||Costa, José L.|
Assis, Carlos A.
Almeida, Pedro R.
Costa, Maria J.
|Keywords: ||Tagus River|
Brackish and freshwater
Feeding and condition
|Issue Date: ||2008|
|Abstract: ||A total of 1,816 eels were sampled in
1988, from seven sampling areas. Four areas were
located in brackish water and the remaining three
were located in freshwater reaches of the
Tagus river basin. Eels were more abundant in
the middle estuary and decreased both in the
upstream and in the downstream directions, with
a predominance of males in higher density areas.
Smaller individuals preferred more peripheral areas, such as margins and upper reaches in the
brackish water zone, and the tributaries of the
freshwater habitats. It was assumed that this
distribution pattern resulted from three main
factors: (i) the dominance of larger specimens;
(ii) the need to avoid predators and; (iii) the
search for better trophic conditions. The condition
of the individuals generally decreased toward
the upper reaches, apparently due to a corresponding
decrease in feeding intensity. The presence
of the Belver dam in the main river, 158 km
upstream from the sea, seemed to impose major
alterations to the described patterns. The concentration
of specimens below this impassable
obstacle yielded a reduction in the proportion of
females and a decrease in the condition and
survival of the eels, contributing to a reduction in
the spawning success of this population. Suggestions
to diminish the effects of the dam, and to
preserve the fishery are also presented.|
|Appears in Collections:||BIO - Publicações - Artigos em Revistas Internacionais Com Arbitragem Científica|
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