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

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Análisis del proceso de recolonización del tramo afectado del Guadiamar otters, Delibes et al., 2009). These studies have reported diverse results about the remaining spill influence. Nonetheless, the few studies that addressed the recovery of fish assemblages (Fernández-Delgado and Drake, 2008; Pérez-Alejandre; 2009) provided ambiguous early conclusions that considered an ongoing recolonization process that tends to the pre-disturbance conditions. The purpose of this study was to evaluate the long-term effects of the Aznalcollar toxic spill on the Guadiamar River fish assemblage. The specific objectives were to: (1) study the recolonization process, pinpointing the main colonist sources, obstacles and dominant species dynamics; and (2) assess whether the fish assemblage in the affected reach can be considered recovered 13 years after the toxic spill. 79
Las comunidades de peces del río Guadiamar y el accidente minero de Aznalcóllar Material and Methods Study area and sampling design The Guadiamar River basin is located in the South-western Iberian Peninsula covering an area of 1.880 km 2 (Borja et al., 2001) (Fig. 1). The upper section flows through the western Sierra Morena, with typical xeric Mediterranean forests. Thereupon, the river crosses a predominantly agricultural area on sedimentary hills and, finally, the southern end turns into a channelized marsh stretch that flows into the Guadalquivir river mouth within the Doñana National Park (Borja et al., 2001). From a hydrological point of view the Guadiamar is a typical Mediterranean river (Giudicelli et al., 1985), with a severe summer drought, annual average temperature above 10 ºC and annual average rainfall of 600 mm (Aguilar et al., 2003). The main river network in the basin consist of the Guadiamar River main stem and its most important tributaries, such as the Agrio River, the Ardachón stream, the Alcarayón stream, the De la Cigüeña stream and the Majaberraque stream (Fig. 1). This Agrio River, located in the boundary between the upper and middle section of the basin, was the first watercourse to receive the spill and hence, it flowed to the Guadiamar River mouth into the Doñana National Park (Fernández-Delgado and Drake, 2008; Fig. 1). Fish assemblage was monitored at five sampling sites located in the Guadiamar River main stem (longitudinal sampling design). Due to the need for quick information after the spill, each site was selected according to accessibility and trying to maximise coverage of the affected fluvial reach. Unfortunately, the hazardous nature of the toxic spill and rapid decomposition of fish impeded collection or identification of dead fishes. Therefore, these fish kill data could not be used to quantify pre-disturbance fish assemblage structure. On the other hand, available information on the Guadiamar River fish assemblage before the spill was scarce. The closest pre-disturbance survey was carried out in 1996 and it provided species presence/absence data (species richness) from the same locations within the affected reach that were subsequently used as sampling points (pre-disturbance data) (Doadrio, 1996 and 2001). Given this scarce previous information, an additional sampling site was established 6 km upstream from the affected reach to represent non-affected assemblage conditions in the context of the mining spill, hereafter referred to as reference site (E1 in Fig. 1). Downstream, within the affected reach, the four original sampling sites were named E2, E3, E4 and E5 (Fig. 1). The first site affected by the spill (E2) was located at the confluence with the Agrio 80
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DEPARTAMENTO DE ZOOLOGÍA UNIVERSID
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DEPARTAMENTO DE ZOOLOGÍA UNIVERSID
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TITULO DE LA TESIS: LAS COMUNIDADES
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A mi Madre,
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A mis antiguos compañeros del Grup
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Material and Methods 39 Results 45
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ABSTRACT This PhD Thesis analyzes t
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Las comunidades de peces del río G
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ÁREA DE ESTUDIO Cuenca del río Gu
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Área de estudio Figura 1. Cuenca d
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Área de estudio farallón del Alja
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Área de estudio Principales impact
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PARTE I: Ictiofauna de la cuenca de
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Page 50 and 51: Condición somática de L. sclateri
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Appendix 1. Environmental variables
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