Richness in Native Fish of Mediterranean Rivers
13 January 2012SPAIN - Researchers at the Universitat Politècnica de València’s Research Institute for the Integrated Management of Coastal Areas (IGIC), have shown the important effect that removing artificial obstacles in Mediterranean rivers can have for the conservation of indigenous fish species.
This is one of the conclusions of a study conducted by UPV researchers Esther Julia Olaya, Francisco Martínez Capel, Rui Costa, and Juan Diego Alcaraz-Hernández.
The objective of their research is to facilitate the efficient and sustainable management of river biodiversity, by developing a predictive model that allows us to anticipate the results of restoration actions in altered sections of rivers before they are undertaken. Researcher Francisco Martínez Capel points out that this is especially important in Mediterranean-climate river basins, where human impacts threaten the extinction of many native species. "With this model we aim to facilitate more efficient decision-making; some very efficient decisions can also be very simple: for instance, removing obsolete dams," said Martínez Capel.
According to the new predictive model, one of the most influential factors in the richness in native fish of Mediterranean rivers is the absence of artificial barriers. Researcher Esther Julia Olaya says that “a simulation has shown that the number of native fish increases as the length of river which is free of artificial barriers increases. Dams, regardless of their size, behave as physical barriers that impede the migration of fish; they also affect sediment transfer and the dispersion of vegetation, and favour the spread of invading foreign organisms, which has a negative influence on indigenous wildlife and flora.”
The study showed that removing obsolete dams can double the population of native species in some parts of Mediterranean rivers. These barriers also affect other variables which are critical to the health of native fish, such as the percentage of stream habitats. Researcher Esther Julia Olaya notes that "some Mediterranean fish species use this kind of habitat, whereas exotic species prefer pools." Also the average annual flow of rivers and its coefficient of variation affect the organisation of Mediterranean aquatic communities, "as the biology of Mediterranean species has features that are associated with fluctuating and unpredictable environments." Water quality is another important factor in the development of fish communities.
The study, the results of which were recently presented at the SCARCE second Annual Conference, is the result of one of the main lines of work of the UPV’s Research Institute for the Integrated Management of Coastal Areas: developing models and technology which can improve the management of coastal areas and aquatic ecosystems, where the impact of human activity is greater. The research was funded by the Spanish Ministry of Science and Innovation through the Consolider-Ingenio 'SCARCE' project and the POTECOL (Plan Nacional de I+D+i) project.
Rivers and artificial neural networks
The IGIC research team chose a predictive model of the "artificial neural networks" kind. The objectives of the study were predicting the richness in native species, determining the influence on this richness of each environmental variable, and simulating mitigation measures for the potential improvement of the ecological status of two segments of the river Xúquer/Júcar. The study area included the main courses of the Xúquer/Júcar, Cabriel and Túria river basins.
The richness in native fish species was determined using the electric fishing method in the spring and summer months of the period 2005-2009. The variables used in the construction of the artificial neural network were 24, and were selected according to their degree of importance to fish life and their availability in public records of water quality. "The artificial neural network that we used was a multilayer perceptron (MLP), which is the most suitable one for ecological studies", says Francisco Martínez Capel.
From their work, researchers at the UPV Gandia Campus concluded that the most important variables for predicting the richness in native fish are the length of river which is obstacle-free, the river stream rate, the quality of the riparian forest, the drainage area, the coefficient of intra-annual variation of the monthly average flow, the average annual flow and the IBMWP (Iberian Biological Monitoring Working Party) index, which assesses the water quality of rivers.
TheFishSite News Desk
Mainstream Canada Dixon Bay Farm is Now Empty
23 May 2012AquacultureUK 2012 Opens Today
23 May 2012
Plan Set For Aquaculture & Fisheries Bill
23 May 2012
New Means of Safeguarding World Fish Stocks
23 May 2012
OIE: ISA Outbreak Reported in Norway
22 May 2012
© 2000 - 2012. 5m Publishing, Benchmark House, 8 Smithy Wood Drive, Sheffield, S35 1QN, England. - A Benchmark Holdings Ltd. Company