Fish Community of the Lacanja River, Chiapas, Mexico. Rocio Rodiles-Hernandez. El Colegio de la Frontera Sur. Carretera Panamericana y Periferico Sur S/N.
Patterns in the Species Diversity and Composition of the Fish Community of the Lacanja River, Chiapas, Mexico Rocio Rodiles-Hernandez El Colegio de la Frontera Sur Carretera Panamericana y Periferico Sur S/N C.P. 29290, San Cristdbal de las Casas. Chiapas, Mexico
Edmundo Dfaz-Pardo Escuela National de Ciencias Bioldgicas
Institute Politecnico National Plan de Ayala y Carpio S/N, Santo Tomas C.P. 11340, Mexico, D.F., Mexico
and John Lyons Wisconsin Department of Natural Resources and University of Wisconsin Zoological Museum 1350 Femrite Drive Monona, Wisconsin 53716-3736 USA
ABSTRACT The Lacanja River, a tropical rain forest river in southern Mexico, remains relatively undegraded and serves as a good reference for comparison with other rivers in the region that are experiencing human impacts. We sampled 12 sites from the headwaters to the mouth of the river (120 km) in both the wet and dry seasons to quantify longitudinal and seasonal patterns in fish community diversity and composition. We collected 44 species (41 native) from the river, with Cichlidae the most speciose family. The most widespread and abundant species were Brycon guatemalensis, Astyanaxsp. (both Characidae), and Cichlasoma intermedium (Cichlidae). Based on fish species composition, the river could be divided into an upper, middle, and lower zone; waterfalls impeded fish movements within and between these zones. The upper zone had the lowest species diversity, and the lower zone had the highest. All of the upper zone fishes also occurred in the lower zone, and community composition changed from upstream to downstream solely through species addition and without species replacement. Overall, species diversity was slightly higher in the dry season. INTRODUCTION Although they are economically and scientifically important, the diverse fish communities of the tropical rain forest rivers of southern Mexico have been little studied. Most of the available information about the fish of these rivers concerns taxonomy and broad-scale distribution patterns (e.g., Regan 1908, Miller 1966, 1986, Lozano-Vilano and Contreras-Balderas 1987, Espinosa-Perez et al. 1993, Gaspar-Dillanes 1996), and there are few studies of species life history and ecology (but see Chavez-Lomeli et al. 1989). Many rivers remain largely unsurveyed, and data on spatial and temporal patterns of fish species diversity and composition are lacking. Unfortunately, rivers in southern Mexico are increasingly degraded by watershed deforestation, oil and mineral 455 Journal of Freshwater Ecology, Volume 14, Number 4 - December 1999
