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

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Table 1. Mean habitat variable values for each sampling site. S: Fish species richness. H’: Fish diversity (Shannon’s diversity index). QBR: Riparian Ecosystems Quality Index. IBMWP: Iberian version of the Biological Monitoring Working Party. IBG: Indice Biologique Global. L. sclateri density and Fish density were removed from the model selection protocol due to lack of data in G6 and G8 due to field sampling constraints. Condición somática de L. sclateri en el Guadiamar 41
Las comunidades de peces del río Guadiamar y el accidente minero de Aznalcóllar Statistical analyses The statistical analyses used to compare fish condition followed those used in two previous studies that dealt with the same species (Oliva-Paterna et al., 2003a and 2003b) and those proposed by García-Berthou and Moreno-Amich (1993). They include the application of univariate analysis of covariance (ANCOVA) using TM (total mass) as the dependent variable and FL (furcal length) as the covariate, and "sampling site" as factor. The relationship between TM and FL was clearly non-linear; therefore, the logtransformation of TM was used as dependent variable and log-transformation of FL as the covariate. We tested the homogeneity of the regression coefficients (parallelism as the assumption of equal slopes) of the dependent-covariate relationship with an ANCOVA design that analysed the pooled covariate-by-factor interaction. If the covariate-by-factor interaction (homogeneity of slopes) was not significant (p > 0.05), we developed a standard ANCOVA to test for significant differences in parameter a (the y-intercept) between populations as a condition index. Additionally, the condition of L. sclateri was represented by residuals obtained from a least squares regression between TM and FL of all captured individuals (logtransformed data) (Sutton et al., 2000). This residual index (Kr) provides an alternative to other more traditional condition indices, e.g. relative condition factor and Fulton’s condition factor, and removes body length effects. Some authors (García-Berthou 2001a, among others) have pointed out dangers in calculating residuals. However, later studies have demonstrated significant correlations between residuals and fat stores (Schulte-Hostedde et al. 2005). First, some of the key assumption underlying the use of residuals were verified: (1) the mass-length relationship was linear, (2) the residual index was independent of length (Regression test ANOVA F (1,759)= 0.21 p=0.889), and (3) the parallelism assumption. Secondly, the mean condition for L. sclateri at each site level was determined from the average Kr of individuals captured at each sampling site. The existence of significant differences between sampling sites was verified by ANOVA analysis and Tukey’s HSD post hoc tests (Quinn and Keough, 2002). Finally, we performed multiple regression analyses to determine the amount of variation in parameter a (the y-intercept) and Kr (residual index) associated with environmental variables. In order to reduce the number of predictor variables and detect the potential occurrence of collinearity, a bivariate analysis was carried out using Pearson’s correlations between all quantitative variables, and Spearman’s correlations for categorical variables (seasonal water flow, dominant substrate and land use index) 42
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DEPARTAMENTO DE ZOOLOGÍA UNIVERSID
Page 4 and 5: DEPARTAMENTO DE ZOOLOGÍA UNIVERSID
Page 6 and 7: TITULO DE LA TESIS: LAS COMUNIDADES
Page 8: A mi Madre,
Page 11 and 12: A mis antiguos compañeros del Grup
Page 13 and 14: Material and Methods 39 Results 45
Page 15 and 16: ABSTRACT This PhD Thesis analyzes t
Page 17 and 18: Las comunidades de peces del río G
Page 25 and 26: ÁREA DE ESTUDIO Cuenca del río Gu
Page 27 and 28: Área de estudio Figura 1. Cuenca d
Page 29 and 30: Área de estudio farallón del Alja
Page 31 and 32: Área de estudio Principales impact
Page 34: PARTE I: Ictiofauna de la cuenca de
Page 48 and 49: II.1- Habitat quality affects the c
Page 50 and 51: Condición somática de L. sclateri
Page 66 and 67: II.2- Habitat-fish community relati
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
Page 99 and 100: Table 1. List of the fish species c
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Las comunidades de peces del río G
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Appendix 1. Environmental variables
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