The dynamics of fish populations in the Palancar stream,a small tributary of the river Guadalquivir,Spain |
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| Institution: | 1. INRA, UR 1115, Plantes et Systèmes de culture Horticoles (PSH), 84000 Avignon, France;2. Departamento de Fitotecnia e Fitossanitarismo, Universidade Federal do Paraná (UFPR), Rua dos Funcionários 1540, CEP 80035-050, Curitiba, Paraná, Brazil;1. CIRAD, UPR GECO, F-97285 Le Lamentin, Martinique;2. CIRAD, UPR GECO, F-34398 Montpellier, France;3. Departamento de Agricultura y Agroforesteria, CATIE, CR-30501 Turrialba, Costa Rica;1. Department of Biological Sciences and Biotechnology, Botswana International University of Science and Technology (BIUST), Private Bag 16, Palapye, Botswana;2. UMR IRD 247 Laboratoire Evolution, Génomes, Comportement et Ecologie, Diversité, Ecologie et Evolution des Insectes Tropicaux, CNRS, Gif-sur-Yvette, France and Université de Paris-Sud, Orsay, France;3. African Insect Science for Food and Health (icipe), Nairobi, Kenya;4. South African Sugarcane Research Institute (SASRI), Private Bag X02, Mount Edgecombe, South Africa;5. Department of Conservation, Ecology and Entomology, Stellenbosch University, Private Bag X01, Matieland, South Africa;6. Department of Crop Production, Faculty of Agriculture, University of Swaziland, Luyengo, Swaziland;7. School of Plant Sciences, Haramaya University, P.O. Box 138, Diredawa, Ethiopia |
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| Abstract: | The relationship between flooding and changes in the size distribution of fish populations in the Palancar stream confirms observations in other rivers. On average, density decreased by 36.2 % and biomass increased by 14.5 %, passing from a period of severe drought to one of heavier than normal rains. Precipitation is the most important of the many factors affecting the populations of the Palancar stream; the most evident changes all occurred after the drought. During the drought period, the marked seasonal fluctuation in flow was the most important factor regulating the population dynamics. Fish density and biomass varied in proportion to the water volume. During the rainy period, the studied section of the river was found to be an important reproduction and nursery area, with juveniles and individuals of reproduction age dominating. The presence of Micropterus salmoides, an introduced piscivorous species, is another factor affecting the population dynamics in the Palancar stream. The observed absence of age 0+ individuals of the dominant populations is considered a direct effect of predation. |
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