A new biological indicator to assess the ecological status of Mediterranean trout type streams |
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| Institution: | 1. Department of Zoology and Physical Anthropology, Faculty of Biology, Complutense University of Madrid, Ciudad Universitaria s/n, E-28040 Madrid, Spain;2. Department of Environmental Sciences, University of Castilla-La Mancha, E-45071 Toledo, Spain;1. Department of Geography, Honk Kong Baptist University, Kowloon Tong, Hong Kong;2. Global Institute for Water Security, University of Saskatchewan, National Hydrology Research Centre, 11 Innovation Boulevard, Saskatoon, SK S7N 3H5, Canada;3. Department of Soil Science, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK S7N 5A8, Canada;4. Canadian Forest Service, Natural Resources Canada, Northern Forestry Centre, 5320-122 Street, Edmonton, AB T6H 3S5, Canada;5. Environment Canada, University of Saskatchewan, National Hydrology Research Centre, 11 Innovation Boulevard, Saskatoon, SK S7N 3H5, Canada;1. Department of Civil Engineering, Languages and Systems Area, University of Burgos, 09001 Burgos, Spain;2. Leicester School of Pharmacy, De Montfort University, LEI 9BH Leicester, United Kingdom;3. Department of Computer Science, University of Jaén, 23071 Jaén, Spain;4. Institute for Materials Research and Innovation, University of Bolton, BL3 5AB Bolton, United Kingdom;5. School of Computer Science and Informatics, De Montfort University, LEI 9BH Leicester, United Kingdom;1. Civil Engineering Department, Vali-e-Asr University of Rafsanjan, Rafsanjan, Iran;2. Department of Statistics, Vali-e-Asr University of Rafsanjan, Rafsanjan, Iran;3. Water Engineering Department, Vali-e-Asr University of Rafsanjan, Rafsanjan, Iran;1. Laboratory of Applied Ecology, CITAB – Centre for the Research and Technology of Agro-Environment and Biological Sciences, University of Trás-os-Montes e Alto Douro, Vila Real, Portugal;2. Department of Ecology & Evolution (DEE), University of Lausanne, CH-1015 Lausanne, Switzerland;3. Centro de Investigacão em Biodiversidade e Recursos Genéticos (CIBIO), Faculdade de Ciências, Universidade do Porto, Porto, Portugal;4. Faculty of Earth and Life Sciences, VU University Amsterdam, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands;5. College of Resources and Environmental Sciences, China Agricultural University, 2 Yuanmingyuan W. Road, Haidian District, Beijing 100193, China |
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| Abstract: | Fuelled by the generalized degradation of freshwater ecosystems, the development of tools to assess their ecological status has been the focus of intensive research in the last decades. Although fish are one of the key biological quality elements used to describe the ecological status of rivers, fish metrics that accurately respond to disturbances in Mediterranean trout type streams are still lacking. In these systems, multimetric indices are not optimal indicators because of their low species richness and abundances, thus alternative approaches are needed. Since carrying capacity defines the potential maximum abundance of fish that can be sustained by a river, its relationship with actual density (D/K ratio) could be an accurate indicator of population conservation status and consequently of the ecological status of the river. Based on this rationale, we modeled carrying capacity dynamics for 37 brown trout populations during a 12-year study period. We analyzed the response of the D/K ratio to a gradient of increasing environmental harshness and degradation in order to assess its suitability to accurately measure brown trout conservation status. Our results showed that the D/K ratio was highly sensitive to temporal and spatial variations in environmental conditions and the levels of human-induced environmental degradation. Variations in the environmental and human degradation factors included in the best explaining regression models developed for the whole population and by age classes accounted for between 58 and 81% of the variation in the D/K ratio. Likewise, the D/K ratio was sensitive to both general and life stage specific disturbance factors. Further analyses helped identify the factors limiting population abundance. Therefore, the D/K ratio could be an interesting indicator to consider when defining objective management plans and corrective actions in degraded rivers and streams subject to Mediterranean climatic conditions. |
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