Patterns of species richness and introduced species in native freshwater fish faunas of a Mediterranean‐type basin: the Guadiana River (southwest Iberian Peninsula)

Corbacho, Casimiro; Sánchez, Juan Manuel

doi:10.1002/rrr.631

Cited by 50 publications

(45 citation statements)

References 22 publications

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“…Although the difference is solely based in one species with low abundance (largemouth-bass), this result is similar to the one described by some authors for dammed rivers (Corbacho and Sanchez, 2001;Jager et al, 2001;Tiemann et al, 2004). None of the richness metrics showed significant differences between the groups of sites within each stream, despite the existence of studies describing a variation of the total richness in different habitat types of natural rivers (Angermeier and Schlosser, 1989) and a higher value for this metric in the sites located downstream from obstacles (Porto et al, 1999;Cumming, 2004;Poulet, 2007).…”

Section: Discussionsupporting

confidence: 89%

The impact of small physical obstacles on the structure of freshwater fish assemblages

Alexandre

Almeida

2009

River Research & Apps

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Many studies have assessed the effects of large dams on fishes but few have examined the effects of small obstacles. Fishes were sampled and environmental variables were characterized at 28 sites in two Iberian streams, 14 located immediately downstream, upstream and between five small obstacles at river Muge and 14 at river Erra, considered as the reference stream. Multivariate analysis indicated that habitat variables like current velocity and depth, but not physicochemistry, were mainly responsible for site groups' discrimination in both streams. The reference stream exhibited a longitudinal gradient of current velocity that, however, was not strong enough to cause significant changes in the fish assemblage's composition and structure. By successive and drastically repeating this gradient near each structure, the obstacles stream presented differences in fish fauna between the three site types. Lentic upstream sites presented higher density of limnophilic, omnivorous and exotic species, like gudgeon Gobio lozanoi, which are well adapted to this type of habitat. Downstream and between obstacles sites were characterized by the dominance of rheophilic and invertivorous taxa, especially barbel Luciobarbus bocagei. Richness metrics did not differ among site types, but diversity was higher in sites located between the obstacles away from its direct influence, where the habitat diversity was higher. Contrarily to upstream sites, downstream and between obstacles sites were similar in many of the studied features to the reference stream, implying that this type of structures cause a higher modification in the upstream fish community. This study suggests that the effects of small obstacles on habitat and fishes are similar, in some extent, to those reported for larger dams, providing important considerations for riverine ecosystem conservation efforts.

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Section: Discussionsupporting

confidence: 89%

The impact of small physical obstacles on the structure of freshwater fish assemblages

Alexandre

Almeida

2009

River Research & Apps

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“…Both species richness and abundance tend to increase toward downstream reaches in response to the increase in living space and environmental stability (Magalha˜es et al 2002). Most invasive fish species introduced to Iberian freshwaters occupy stable habitats, often lentic systems (Corbacho and Sa´nchez 2001, Elvira and Almodo´var 2001, Ribeiro et al 2008, and few of them are able to cope with the extreme flow fluctuations in small Mediterranean streams (VilaGispert et al 2005). The milder environmental fluctuations that occur in reservoirs, and their proximities, and in downstream reaches would favor the successful establishment of invasive species populations (Moyle and Light 1996, Corbacho and Sa´nchez 2001, Ribeiro et al 2008.…”

Section: Discussionmentioning

confidence: 99%

Invasive species and habitat degradation in Iberian streams: an analysis of their role in freshwater fish diversity loss

Hermoso

Clavero

Blanco³

et al. 2011

Ecological Applications

169

124

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Abstract. Mediterranean endemic freshwater fish are among the most threatened biota in the world. Distinguishing the role of different extinction drivers and their potential interactions is crucial for achieving conservation goals. While some authors argue that invasive species are a main driver of native species declines, others see their proliferation as a co-occurring process to biodiversity loss driven by habitat degradation. It is difficult to discern between the two potential causes given that few invaded ecosystems are free from habitat degradation, and that both factors may interact in different ways.Here we analyze the relative importance of habitat degradation and invasive species in the decline of native fish assemblages in the Guadiana River basin (southwestern Iberian Peninsula) using an information theoretic approach to evaluate interaction pathways between invasive species and habitat degradation (structural equation modeling, SEM). We also tested the possible changes in the functional relationships between invasive and native species, measured as the per capita effect of invasive species, using ANCOVA.We found that the abundance of invasive species was the best single predictor of natives' decline and had the highest Akaike weight among the set of predictor variables examined. Habitat degradation neither played an active role nor influenced the per capita effect of invasive species on natives. Our analyses indicated that downstream reaches and areas close to reservoirs had the most invaded fish assemblages, independently of their habitat degradation status. The proliferation of invasive species poses a strong threat to the persistence of native assemblages in highly fluctuating environments. Therefore, conservation efforts to reduce native freshwater fish diversity loss in Mediterranean rivers should focus on mitigating the effect of invasive species and preventing future invasions.

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“…Particularly in Mediterranean rivers, pollution, introduction of exotic species and alteration of hydrological regimes have influenced fish population decline and, in some cases, the extinction of native species Smith and Darwall, 2006). According to IUCN, 56% of freshwater Mediterranean species are threatened (Smith and Darwall, 2006) and, given the high degree of endemicity of biota and its high vulnerability to habitat alteration, more research is currently needed on local and native fish populations (Corbacho and Sánchez, 2001;Doadrio, 2002). The conservation of fish diversity is one of the most critical issues facing the preservation of Mediterranean biodiversity (Smith and Darwall, 2006); and, due to its sensitivity to human disturbances, fish species richness is widely used as a primary indicator of ecological change and as a criterion for the selection of conservation areas (van Jaarsveld et al, 1998;Lek et al, 2005;He et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

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

Olaya-Marín

Martínez‐Capel

Vezza

2013

Knowl. Managt. Aquatic Ecosyst.

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Key-words:Artificial neural networks, random forests, native fish, species richness, Mediterranean rivers Machine learning (ML) techniques have become important to support decision making in management and conservation of freshwater aquatic ecosystems. Given the large number of ML techniques and to improve the understanding of ML utility in ecology, it is necessary to perform comparative studies of these techniques as a preparatory analysis for future model applications. The objectives of this study were (i) to compare the reliability and ecological relevance of two predictive models for fish richness, based on the techniques of artificial neural networks (ANN) and random forests (RF) and (ii) to evaluate the conformity in terms of selected important variables between the two modelling approaches. The effectiveness of the models were evaluated using three performance metrics: the determination coefficient (R 2 ), the mean squared error (MSE) and the adjusted determination coefficient (R 2 adj ) and both models were developed using a k-fold crossvalidation procedure. According to the results, both techniques had similar validation performance (R 2 = 68% for RF and R 2 = 66% for ANN). Although the two methods selected different subsets of input variables, both models demonstrated high ecological relevance for the conservation of native fish in the Mediterranean region. Moreover, this work shows how the use of different modelling methods can assist the critical analysis of predictions at a catchment scale. RÉSUMÉUne comparaison des réseaux de neurones et des forêts aléatoires pour prédire la richesse en espèces de poissons indigènes dans les rivières méditerranéennes Les techniques d'apprentissage automatique (ML) sont devenues importantes pour aider à la décision dans la gestion et la conservation des écosystèmes aquatiques d'eau douce. Étant donné le grand nombre de techniques ML pour amélio-rer la compréhension de l'utilité des ML en écologie, il est nécessaire de réaliser des études comparatives de ces techniques comme analyse préparatoire pour des applications de modèles futurs. Les objectifs de cette étude étaient : (i) de comparer la fiabilité et la pertinence écologique de deux modèles prédictifs pour la richesse de poisson, basé sur les techniques de réseaux de neurones artificiels (ANN) et les forêts aléatoires (RF) et (ii) d'évaluer la conformité en termes de sélection des variables importantes entre les deux approches de modélisa-tion. L'efficacité des modèles a été évaluée au moyen de trois indicateurs de Article published by EDP Sciences E.J. Olaya-Marín et al.: Knowl. Managt. Aquatic Ecosyst. (2013) 409, 07 performance : le coefficient de détermination (R 2 ), l'erreur quadratique moyenne (MSE) et le coefficient de détermination ajusté (R 2 adj ) et les deux modèles ont été développés en utilisant une procédure de validation croisée k-fold. Selon les résul-tats, les deux techniques ont des performances de validation similaires (R 2 = 68 % pour RF et R 2 = 66 % pour ANN). Bien que les deux...

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Patterns of species richness and introduced species in native freshwater fish faunas of a Mediterranean‐type basin: the Guadiana River (southwest Iberian Peninsula)

Cited by 50 publications

References 22 publications

The impact of small physical obstacles on the structure of freshwater fish assemblages

The impact of small physical obstacles on the structure of freshwater fish assemblages

Invasive species and habitat degradation in Iberian streams: an analysis of their role in freshwater fish diversity loss

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

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