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 and Guadiamar rivers, whereas E3, E4 and E5 were situated 9 km, 19 km and 26 km, downstream of this confluence, respectively (monitoring stretch-: 32 Km from E1 to E5, Fig. 1). For our objective of evaluating fish assemblage recovery processes, we assumed that all the affected sampling sites (E2, E3, E4 and E5) began the recovery from the same state of disturbance. Figure 1. Location of the Guadiamar River basin where main river network, longitudinal sampling sites, affected reach, non-affected sampling sites in the main tributaries and potential major chemical and physical barriers are shown. 81
Las comunidades de peces del río Guadiamar y el accidente minero de Aznalcóllar The Guadiamar River network is disrupted by several physical and chemical barriers. Some of these disturbances represent an important interruption to fish movement and therefore, an obstacle for recolonization processes. The Agrio reservoir in the Agrio River is the largest transversal obstacle in the watershed. Nevertheless, two other major barriers located in the Guadiamar River main stem were likely a direct obstacle to fish recolonization from downstream sources. Los Molinos mill is placed 2 km downstream of the lowest sampling site (E5) in the longitudinal design. This ancient mill dam (height = 2 m) has a drain that allows some flow to pass below the structure. Upstream, La Patera mill is the second obstacle that potential downstream colonists find. This former weir (height = 1.5 m) is located between E5 and E4, at 3 km and 4 km from these points, respectively. Moreover, three major chemical barriers may also hamper the recolonization process. Specifically, leachates from Aznalcóllar mines to the Agrio River in the upper section (Cabrera et al., 1984, 1987; Arambarri et al., 1996); sewage from Pilas towards the lower section of the Alcarayón stream in the middle section (Fernández-Delgado et al. 2010); and sewage from Hinojos and Villamanrique de la Condesa to the channelized De la Cigüeña stream in the lower section (Fernández- Delgado et al. 2010). Fish were sampled once a year at each sampling site at the time of low annual flow (July-August) for nine years. Because of safety restrictions and cleaning works after the spill, the first sampling was carried out in 1999, and monitoring was uninterrupted until 2006. Additional funds allowed a last sampling effort in 2011. Altogether, 45 surveys were conducted in this longitudinal sampling design. Monitoring at the five sampling sites took place in streches with low-flow conditions (runs or pools); water width and depth of sampling stretches averaged 15 m and 2 m, respectively; clay and sand were the predominant substrate, with some gravel and a few boulders. At site level, fish were caught using two passive sampling methods: (i) setting ten minnow-traps (Harrison et al., 1986; 0.5 m length, 0.03 m diameter entrance), distributed only in the bank of pools, for roughly 18 hours; and (ii) one multi-mesh gillnet (30 m long and 1.5 m deep) placed transversely running from the bank of pools, with mesh sizes ranging from 10 mm to 200 mm, soaking time approximately 18 hours. In addition, the most important tributaries that flow into the Guadiamar River main stem (Fig. 1) and a Guadiamar stretch, just downstream of the river-marsh transition (Doñana marshland), were sampled and considered as non-affected fish 82
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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 48 and 49: II.1- Habitat quality affects the c
Page 50 and 51: Condición somática de L. sclateri
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Page 68 and 69: Relaciones peces/hábitat en el Gua
Page 76 and 77: Figure 2. Tributary network of the
Page 86: PARTE III: Evolución de la comunid
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Appendix 1. Environmental variables
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