Abstract
The distribution and abundance of fish is influenced by multiple factors at temporal and spatial scales, and their community composition represent good river integrity indicators. The main objective of this study was to describe the composition and structure of fish assemblages along the Anchique river sub-basin (that drains to Magdalena river), and to test the hypothesis that these communities vary temporally and spatially. For this, four sites (E1, E2, E3 and E4) were sampled along the river (from river birthplace to Magdalena river), during the periods of high and low waters, in 2014. In each site, longitudinal transects (100 m long x 2 m wide, 60 min) were established and fishing was made with both electrofishing and trawl (10 m x 1 m, 0.05 m) nets. Fish samples were fixed and transported to the laboratory for posterior taxonomic identification with the use of keys; fish diversity and structure composition were calculated with the use of standard models. Besides, substrate composition and environmental variables were also considered. A total of 652 fish belonging to 36 species were recorded; high water showed higher values (325 fish with 32 species) than low water period (300 fish with 31 species). Siluriformes was dominant (51 %), followed by Characiformes (32 %), Gymnotiformes (5 %), Cyprinidontiformes and Cichliformes (6 %). Most abundant families were Characidae (28.3 %; 9 spp.), Loricariidae (23.4 %; 8 spp.) and Trichomycteridae (15.0 %; 2 spp.). Kruskal-Wallis test indicated that there is no significant difference among some environmental variables at the temporal level. The values of structural complexity and substrate composition indices showed that E4 had the highest values (0.8), followed by E1 (0.6), and E2 and E3 (0.4). Moreover, E4 had the highest richness and diversity, according to Hill’s number. The canonical correspondence analysis showed that the substrate, and the complexity and width of the river channel, had a significant influence on fish composition and distribution. The fish community richness and diversity did not change temporarily, but did spatially, which could be related to the different structural features of sampling sites.
Highlights
Las características estructurales de los ecosistemas acuáticos tropicales tienen influencia sobre la composición de las comunidades ícticas
The distribution and abundance of fish is influenced by multiple factors
that drains to Magdalena river
Summary
Área de estudio: El estudio se desarrolló en la cuenca del río Anchique, el cual tributa directamente al río Magdalena, y se localiza en la zona de vida bosque seco tropical (bs-T), departamento de Tolima, Municipalidad de Natagaima, Colombia. Para determinar la existencia de diferencias estadísticamente significativas entre variables físicas y fisicoquímicas de las estaciones de muestreo a nivel espacial y temporal, se realizó una prueba no paramétrica de una vía de Kruskal-Wallis. Influencia de los factores ambientales: Con el fin de determinar si las variables ambientales (incluyendo los valores del índice de composición del sustrato y complejidad estructural del hábitat) influyeron en la estructura de la comunidad de peces, se realizó un análisis de ordenación. No se encontraron diferencias estadísticamente significativas entre las variables fisicoquímicas del río entre periodos climáticos (Kruskal-Wallis, pH p = 0.7728; dureza p = 0.7728; alcalinidad p = 0.5637, conductividad eléctrica p = 0.6631, oxígeno disuelto p = 0.08326; sólidos totales p = 0.1465 y temperatura del agua p = 0.3719). CUADRO 1 Variables físicas y químicas por estación de muestreo de la microcuenca del río Anchique, Tolima, Colombia
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