Topological analysis of the ecological importance of elasmobranch fishes: A food web study on the Gulf of Tortugas, Colombia |
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Authors: | Andrés F Navia Enric Cortés Paola A Mejía-Falla |
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Institution: | a Fundación Colombiana para la Investigación y Conservación de Tiburones y Rayas, SQUALUS, Carrera 79 No 6-37, Cali, Colombia b Grupo de Investigación en Ecología Animal, Departamento de Biología, Universidad del Valle. A.A. 25360, Cali, Colombia c Programa de Doctorado en Ciencias Marinas, Centro Interdisciplinario de Ciencias Marinas, A.P. 592, La Paz, B.C.S. Mexico d National Oceanographic and Atmospheric Administration, National Marine Fisheries Service, Panama City, FL 32408, USA |
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Abstract: | We built a trophic network based on a matrix of interspecific trophic relationships to assess the role of elasmobranch fishes in shaping community structure of the Gulf of Tortugas in the Colombian Pacific Ocean. We analyzed diet similarities to define trophic components (nodes) - rather than taxonomical groups - in the network. We evaluated the ecological function of species or trophic entities through topological analysis of their structural importance in trophic networks by applying one local and several mesoscale network indices. We found that top predatory elasmobranchs play an important ecological role in top-down control and in propagating indirect effects through the system owing to high values of the node degree, centrality and topological importance indices. However, invertebrates and teleost fishes had higher connectivity and topological importance than other elasmobranchs in the network before and after removal of top predators from the system. Results from our study thus suggest that elasmobranchs at intermediate trophic levels - commonly referred to as “mesopredators” - are not so important in all complex coastal ecosystems as previously reported. |
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Keywords: | Sharks Skates Rays Food webs Key species Mesopredators |
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