Morphological Variations of Wild Populations of Brycon dentex (Characidae, Teleostei) in the Guayas Hydrographic Basin (Ecuador). The Impact of Fishing Policies and Environmental Conditions

SIMPLE SUMMARY: The conservation status of a native fish species is often a key indicator of the state of habitat alteration, which supports strong anthropogenic disturbance. Ecuador contains the Guayas basin, the largest basin in the Pacific Ocean, which is a biodiversity reserve. However, there is little information regarding the morphometric characterization of Brycon dentex and its variations within this basin, although its plasticity has been proposed as an indicator of the maintenance of biodiversity. The goal of this study was to analyze the effects of anthropogenic activity and habitat modification on the morphological variation of Brycon dentex and to determine the usefulness of discriminant analysis in the morphometric differentiation of three populations of Brycon dentex in Ecuador. The Brycon dentex morphometric model could be used as a framework in conservation and, thus, an indicator of habitat status by quickly detecting changes in fish shape. ABSTRACT: The Guayas, located in Ecuador, is the largest basin in the Pacific Ocean and has an inventory of 123 native freshwater species. Most of these are endemic species that are threatened or at-risk due to anthropogenic activity and the modification, fragmentation, and destruction of habitats. The aim of this study was to determine the morphometric variation in three wild populations of Brycon dentex in the Guayas basin rivers and their connections to fishing management and environmental conditions. A total of 200 mature fish were captured, and 26 morphometric parameters were measured. The fishing policies (Hypothesis 1) and environmental conditions (Hypothesis 2) were considered fixed factors and were validated by t-tests. The morphological variation among the three populations (Hypothesis 3) was validated through a discriminant analysis. Fishing policies and resource management were found to generate morphological differences associated with body development. In addition, the environmental conditions were found to influence the size and structure of Brycon dentex populations. The analyzed populations were discriminated by the generated morphometric models, which differentiated Cluster 1 (Quevedo and Mocache rivers) with high fishing pressure from Cluster 2 (Pintado river) with medium–low fishing pressure. Morphometric differentiation by discriminant analysis is a direct and economic methodology that can be applied as an indicator of diversity maintenance.