Development and evaluation of a fish-based index to assess biological integrity of Mediterranean streams

Abstract

A multimetric Index of Biotic Integrity (IBI) based on fish data was developed to assess the ecological status of Iberian streams, in the context of the European Water Framework Directive. Fish assemblages were determined by electrofishing at 114 sites from 10 basins of the Júcar River Basin District. The sampled streams were typical Mediterranean streams with strong variation in flow, a species-poor and tolerant fish fauna, and low ecological specialization of the fish species. These features make it difficult to employ metrics based on species richness, trophic specialization, and reproductive strategy, which are typical of IBIs and similar indices. The proposed IBI (IBI-Jucar) is composed of five metrics related to fish health, age-structure, and abundance and richness of native and alien species. IBI-Jucar was validated by demonstrating high correlation with various measures of environmental degradation and with several biotic and habitat indices. It was also highly correlated with the European Fish Index (EFI+), despite different methods used for development and contrasting metrics obtained. The results underline the complementarity of different biotic indices and show that indices based on fish can be a valuable tool for determining environmental quality, even in species-poor Mediterranean streamsAdditional funding was provided by the Spanish Ministry of Science (CGL2009‐12877‐C02‐01 and Consolider‐Ingenio 2010 CSD2009‐00065

A comparison of artificial neural networks and random forests to predict native fish species richness in Mediterranean rivers

“…Although the variables' ranking was not the same (in terms of % of contribution, Figure 5), this accordance can indicate the robustness of the results (e.g. Xu and Zhang, 2001) In several studies (Oberdorff et al, 1995;Reyjol et al, 2007;Leprieur et al, 2009) DRA is considered an important environmental variable for fish species richness, integrating information related to habitat diversity, the variety of microclimates and flow regimes in the river basin (Allan and Castillo, 2007;Townsend et al, 2008) The negative relationship between DRA and richness may be due to the fact that the lower reaches of Júcar, Cabriel and Turia rivers are highly regulated and have higher levels of contamination than the upper reaches (Aparicio et al, 2011). Water quality and riparian forest play a key role in determining the richness of native fish Thus, QBR and IBMWP have been identified as relevant factors positively influencing fish species richness in Spain (Carballo et al, 2009;Sánchez-Montoya et al, 2010) and are widely used for the ecological monitoring of rivers.…”

“…During the last decades, the natural flow regime has been altered by the construction of reservoirs and water diversion structures; flow regulation is severe particularly for streams located in the middle and lower part of the watersheds. The effect of flow regulation is expressed by an inversion of the intra-annual variability pattern; in summer, the regulated flow is greater than natural flow, and in contrast, the regulated flow is smaller than the natural flow during winter (Aparicio et al, 2011). Due to industrial and urban waste water, pollution also affects rivers (Estrela et al, 2004;Aparicio et al, 2011) and agricultural practices, particularly in spring and summer, constitute a source of diffusive pollutants at the catchment-scale (Estrela et al, 2004).…”

“…The effect of flow regulation is expressed by an inversion of the intra-annual variability pattern; in summer, the regulated flow is greater than natural flow, and in contrast, the regulated flow is smaller than the natural flow during winter (Aparicio et al, 2011). Due to industrial and urban waste water, pollution also affects rivers (Estrela et al, 2004;Aparicio et al, 2011) and agricultural practices, particularly in spring and summer, constitute a source of diffusive pollutants at the catchment-scale (Estrela et al, 2004). In the analyses, we used data from 90 sampling sites along the mainstems of the three rivers (Figure 1).…”

“…Moreover, the ecological knowledge of Mediterranean rivers needs to be expanded. Additional efforts to improve the understanding of the main factors influencing species richness are valuable (Filipe et al, 2010;Aparicio et al, 2011). In this context, the objectives of this study were (i) to compare the reliability and ecological relevance of two ML predictive models for fish richness, based on the techniques of ANN and RF and (ii) to evaluate their conformity in terms of selected important variables between the two modelling approaches.…”

Patterns of occurrence of semi-aquatic reptiles in highly invaded Mediterranean rivers

“…The assessment of these characteristics enabled estimation of the heterogeneity of the riverine habitats, based on a fluvial habitat index (Pardo et al 2002). High values of this index are associated with higher native biota diversity in Mediterranean fluvial systems (Pardo et al 2002;Aparicio et al 2011).…”