las comunidades de peces del río guadiamar y el accidente minero ...

I.1- Long-term fish species composition after one of the
worst toxic spills in Europe.
Introduction
The Iberian ichthyofauna includes only a few families, with a high degree of
diversification at the species level and numerous endemisms. These endemisms
compound the 80% of the species that belong to the families Cyprinidae, Cobitidae and
Cyprinodontidae present in the Iberian Peninsula, which reaches the highest endemism
proportion in Europe (Doadrio, 2001; Kottelat and Freyhof, 2007). The isolation from
other European basins, the relatively small size of Iberian drainages and climatic factors
are the main causes of differentiation of many independent and isolated populations
(Clavero et al., 2004). Southern Iberian basins endure long droughts and abrupt floods,
common in the Mediterranean climate (Gasith and Resh, 1999). This variability is the
key to fish assemblage structure (Pires et al., 1999; Magalhaes et al., 2002a, 2002b),
where the watercourse position within the river basin network is determinant (Filipe et
al., 2002). Thereby, the extreme dry conditions in summer cause significant loss of
habitat and connectivity (Matthews and Marsh-Matthews, 2003) and consequently, a
mighty decrease in fish populations. In addition to this naturally fragile balance, water
extraction by humans increase in this season mainly in areas with agricultural and
touristic land uses (Clavero and Hermoso, 2011; Ribeiro and Leunda, 2012), which
cause habitat degradation or destruction by pollution, hydraulic engineering (reservoirs,
channels, etc.), land use changes and exotic species introductions. The sum of these
effects is causing a progressive loss of fish communities in the Iberian drainages
(García-Berthou and Moreno-Amich, 2000, Corbacho and Sánchez, 2001, Clavero et al.
2004; Ribeiro et al., 2008).
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