Patterns of diversity, zoogeography, and ecological gradients in Honduran freshwater fishes

Wilfredo Antonio Matamoros

Abstract

Nineteen major river drainages across Honduras were sampled from 2005-2009 in order to understand Honduran geographical patterns of freshwater fish distribution, to delineate the Honduran freshwater fishes ichthyographical provinces, and to understand patterns of species assemblage at the drainage level. A total of 166 species of freshwater fishes were sampled, a 64% increase over previously published reports. Eight species belong to primary freshwater families, 47 to secondary, and 111 to peripherals. In order to understand the species-drainages relationships, a presence-absence matrix was built for the 19 major drainages and 55 primary and secondary freshwater fishes. Correspondence and cluster analysis clearly separated the Pacific and Atlantic drainages, corresponding to earlier ichthyographical provinces for the region. However, the Pacific slope of Honduras formed a single Ichthyographical province that includes the Lempa, Goascorán, Nacaome, Choluteca, and Negro River drainages. In contrast to earlier studies, the Honduran Atlantic slope was divided in three Ichthyographical provinces: (1) the Motagua-Chamelecón-Ulúa-Ichthyographical Province; (2) the Nombre de Dios and Bay Islands Ichthyographical Province; and (3) the Honduran Mosquitia Ichthyographical Province. In order to study patterns of fish assemblages, eleven sites in two rivers (the Cangrejal and Lancetilla) of the Nombre de Dios and Bay Island Ichthyographical Province were sampled repeatedly over the study period. Sampling localities included lowland (0-10 m above sea level) middle (10-100 m) and upper reaches (>100 m) of both reaches. At each station I used several fishing techniques and also measured physicochemical parameters of the streams. Fish assemblages between the two rivers were found to be significantly different. Significant differences in fish assemblages were also found among the rivers' lower, middle, and upper reaches. However, relationships among assemblage structure and physicochemical variables were weak. Diversity and assemblage structure change most at higher altitude where species diversity is the lowest. Upper reaches habitat are dominated mostly by fishes with strong swimming capabilities (e.g. Mullet), and fishes with morphological adaptations to inhabit and swim through rapids and waterfalls (e.g. gobies).