Effects of multi‐year droughts on fish assemblages of seasonally drying Mediterranean streams

Magalhães, María Filomena; Beja, Pedro; Schlosser, Isaac J.; Collares‐Pereira, Maria João

doi:10.1111/j.1365-2427.2007.01781.x

Cited by 174 publications

(211 citation statements)

References 53 publications

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“…Accordingly, similar pattern in species diversity was observed. These results are in accordance with numerous previous studies (Godinho et al, 1997(Godinho et al, , 2000Carmona et al, 1999;Pires et al, 1999Pires et al, , 2004Mesquita and Coelho, 2002;Magalhães et al, 2002aMagalhães et al, , 2002bMagalhães et al, , 2007Clavero et al, 2004;Ferreira and Oliveira, 2004;Clavero and Garcia-Berthou, 2006;Mesquita et al, 2006;Ferreira et al, 2007aFerreira et al, , 2007b. In fact, increasing local species richness along the longitudinal stream gradient is a very well known pattern (e.g.…”

Section: Figuresupporting

confidence: 82%

Fish-based groups for ecological assessment in rivers: the importance of environmental drivers on taxonomic and functional traits of fish assemblages

Matono

Formigo

Almeida

et al. 2012

Knowl. Managt. Aquatic Ecosyst.

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The use of river-types is of practical value, serving as groups for which assessment procedures can be developed and applied. An abiotic typology was set by the Portuguese Water Agency, mainly based on 6 major morphoclimatic regions. However, to be biologically meaningful, this typology should fit the distribution patterns of the biological quality elements communities proposed in Water Framework Directive under the lowest possible human pressure. This study aimed to identify and characterize fish-based geographical groups for continental Portugal and their environmental and geographical discriptors, using taxonomic and functional traits. Sampling took place between 2004 and 2006 during Spring. Fish fauna from 155 reference sites was analysed using a multivariate approach. Cluster Analysis on fish composition identified 10 fish-groups, expressing a clear correspondence to the river basin level, due to the restrict basin distribution of many species. Groups showed a wider aggregation in 4 regions with a larger geographical correspondence, statistically supported by Similarity Analysis, both on fish composition and mostly on fish metrics/guilds. Principal Components Analysis revealed major environmental drivers associated to fish-groups and fish-regions. Fish-groups were hierarchically grouped over major and local regions, expressing a large-scale response to a North-South environmental gradient defined by temperature, precipitation, mineralization and altitude, and a regional scale response mainly to drainage area and flow discharge. From North to South, fish-regions were related to the morphoclimatic regions. Results contributed to reduce redundance in abiotic river-types and set the final typology for Portuguese rivers, constituting a fundamental tool for planning and managing water resources.

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Section: Figuresupporting

confidence: 82%

Fish-based groups for ecological assessment in rivers: the importance of environmental drivers on taxonomic and functional traits of fish assemblages

Matono

Formigo

Almeida

et al. 2012

Knowl. Managt. Aquatic Ecosyst.

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“…The failure of rainfall leads to a loss of soil moisture, surface runoff and groundwater recharge. In streams with seasonal drought, the biota appear to be well adapted to this predictable hazard, but if such systems are subject to supra-seasonal drought the biota may suffer losses if not local extinctions (Boulton, 2003;Magalhaes et al, 2007). In the early stages of supra-seasonal drought, temporary water bodies, be they standing water or flowing water, may dry up or become reduced to a series of diminishing pools.…”

Section: What Is Drought?mentioning

confidence: 99%

The impacts of drought on freshwater ecosystems: an Australian perspective

2008

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Southeastern Australia is presently experiencing one of the worst droughts observed in the region in the last 200 years. The consequences of drought have been far reaching both for human consumptive uses and for aquatic ecosystems, and serve to highlight several important aspects of the nature of droughts, their ecological impacts, and how humans respond to them. Running water ecosystems are the dominant form of freshwater ecosystem in Australia, yet, despite the high frequency of drought we lack a basic understanding of the consequences of long-term droughts (as distinct from seasonal droughts) as an ecosystem disturbance, and more is known about drought effects on flowing than on standing waters. Drought is well defined and characterised meteorologically, but hydrologically its characterisation is equivocal. While drought severely impacts natural aquatic ecosystems, its effects have been and are exacerbated by direct and indirect anthropogenic modifications to streams and their catchments. In streams the major impacts are the loss of water and habitat availability, and the reduction, if not severing, of connectivity (lateral, longitudinal and vertical). Despite the relative frequency of drought in Australia we have failed to develop long-term management strategies capable of contending with droughts and their impacts, particularly in catchments where human disturbances have reduced the natural resistance and resilience of aquatic ecosystems, and where the demand for consumptive water use is high and rising. Here, we provide a commentary on drought and its implications for the management of freshwater ecosystems. We begin with a general discussion of drought and its impacts on streams and rivers before discussing some of the more specific management issues and response strategies that have arisen in response to the current drought in Australia. Throughout we consider global as well as local examples. We conclude by highlighting important knowledge gaps and by providing some general principles for better incorporating droughts and their impacts into river management strategies.

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“…For this reason, we removed DHS, WAT and ALT as potential predictors. CON and FCV were also highly correlated; we kept FCV as a potential predictive variable because it represents flow variability and it was found important for Mediterranean fish species in several studies (Magalhães et al, 2007;Hermoso and Clavero, 2011) Lastly, FIA and FMA were also correlated; however both of them were used as predictive variables given their similar relevance for Mediterranean fish life cycle (Hermoso and Clavero, 2011). …”

Section: > Environmental Variablementioning

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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Effects of multi‐year droughts on fish assemblages of seasonally drying Mediterranean streams

Cited by 174 publications

References 53 publications

Fish-based groups for ecological assessment in rivers: the importance of environmental drivers on taxonomic and functional traits of fish assemblages

Fish-based groups for ecological assessment in rivers: the importance of environmental drivers on taxonomic and functional traits of fish assemblages

The impacts of drought on freshwater ecosystems: an Australian perspective

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

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