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The Cusiana River sub-basin has been identified as a priority conservation area in the Orinoco region in Colombia due to its high species diversity. This study presents an updated checklist and identification key for fishes of the Cusiana River sub-basin. The checklist was assembled through direct examination of specimens deposited in the main Colombian ichthyological collections. A total of 2020 lots from 167 different localities from the Cusiana River sub-basin were examined and ranged from 153 to 2970 m in elevation. The highest number of records were from the piedmont region (1091, 54.0 %), followed by the Llanos (878, 43.5 %) and Andean (51, 2.5 %). 241 species distributed in 9 orders, 40 families, and 158 genera were found. The fish species richness observed (241), represents 77.7 % of the 314 estimated species (95 % CI=276.1–394.8). The use of databases to develop lists of fish species is not entirely reliable; therefore taxonomic verification of specimens in collections is essential. The results will facilitate comparisons with other sub-basins of the Orinoquia, which are not categorized as areas of importance for conservation in Colombia.

The present study describes ecological aspects of <em>Lebiasina erythrinoides</em>; 200 individuals were sampled throughout an annual hydrological cycle from October 2008 to September 2009 in La Calaboza stream, a Piedmont tributary of the Rio Cravo Sur. The studied population had more females than males (1.5:1) and preferred habitats dominated by shoreline vegetation and rocky substrates. Prior to reproductive events, individuals presented an increase in the condition factor (K) and the gonosomatic index (GSI). On average, 648.8 oocytes are discharged twice a year: at the beginning of the rainy season, and during falling water phase. The mean sizes at sexual maturity found for females were 73.5 mm standard length (SL) and for males 70 mm SL. Rounding up, an average minimum size of capture of 75 mm SL is proposed. Most specimens of the population (65 %) were found to be maturing or mature (stages II and III), 28.5 % immature (stage I), 5.0 % in post reproduction stage V, and 1.5 % in reproductive phase (IV). Results suggest this species is omnivorous with a preference for invertebrates (IRI = 41.2 %) and vegetal material (IRI = 27.8 %), but also includes a variety of other items. The values of the diet are correlated with hydrological cycle and size.

La Orinoquia andina en Colombia ha sido muy afectada por la intervención antrópica. Aunque se han realizado ejercicios de priorización de áreas importantes para la conservación que han incluido a los peces de agua dulce, estos sólo han tenido en cuenta variables como la riqueza, endemismos y estatus de amenaza, que resultan insuficientes para representar la variabilidad geográfica y los patrones de distribución de las especies. En este trabajo, se propone una priorización para la conservación de los peces en la Orinoquia andina a partir de tres enfoques: identificación de áreas de endemismo, riesgo y complementariedad. Los tres enfoques coinciden en la priorización de la subcuenca del río Ariari como la más importante para la conservación de los peces, seguida por la subcuenca del río Guamal, abarcando en conjunto el 72,35 % de la ictiofauna de la Orinoquia Andina. Aunque el 47,07 % del área de estudio pertenece a algún tipo de área protegida, solo el 0,97 % de los registros de peces provienen de áreas protegidas nacionales y el 14,8 % de áreas regionales, resaltando el bajo conocimiento de la diversidad de peces en estas áreas. Se exhorta a las autoridades ambientales, institutos de investigación y universidades, a realizar investigación básica en las áreas protegidas, que permitan conocer su riqueza y analizar su efectividad para conservar la ictiofauna.

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