Trophic and reproductive ecology of Hemibrycon sierraensis (Characiformes: Characidae), endemic fish of Gaira River, Sierra Nevada of Santa Marta, Colombia. The study of feeding habits in fishes can give important information about their role in the fish community, their functional role in the ecosystem, and their relationships with all available resources. We studied H. sierraensis from Gaira River and performed eight bi-monthly samples between May 2014 and November 2015. We analyzed fish stomach contents by the numerical (% N), volume (% V) and frequency of occurrence (% FO) methods; we also calculated the index of food importance (IA), coefficient of emptiness (CV), trophic niche breadth (used H') and condition factor (K). Additionally, we determined the sex ratio, gonadosomatic index (RGS), fecundity, minimum and average size at sexual maturity, and oocyte diameter by standard methods. The Gaira River has irregular meanders with clear waters, and high current velocity through its drainage; it is generally oligotrophic, with a tendency to eutrophic condition in some places. Observed dissolved oxygen values were high (5.4 mg/L), electrical conductivity was 68.63 µS/cm, and pH was found neutral. We analyzed stomach contents of 477 specimens, and found a 1.59 % coefficient of vacuity. The species was found euryphagic in its feeding habits (H'= 0.69), omnivorous tending to insectivorous; its diet consisted mainly of Trichoptera larvae (Atanatolica sp.), followed in importance by snails (Gastropoda Pomacea sp.) and dipteran larvae such as Simulium sp. Significant differences in both frequency of occurrence and the volume consumed were observed for the different size classes, as well as between different seasons of the year. The condition factor indicated that the species was well fed. Sex was determined for 424 fish, of which 241 were male and 183 female, given a ratio of 1.3: 1 (male-female) which resulted significantly different (Chi 2: 16.14; p= 0.02). The gonadosomatic index indicated that reproduction occurs during the high water river phase, fecundity was high, and oocyte diameter was relatively small. Males reached sexual maturity at an average size of 67.08 mm SL, and females at 70.68 mm SL. Their life history strategy is seasonal r. Management and conservation plans for this species are required due to human intervention in their habitat, originated by the growing tourist activity in the area. Rev. Biol. Trop. 65 (3): 1033-1045. Epub 2017 September 01.

El río Gaira, en Minca, SNSM, sufre una transformación acelerada de sus paisajes naturales, fomentada por actividades como el turismo y la agricultura. Esto es preocupante considerando que allí habita una diversidad de especies endémicas como el pez Trichomycterus nigromaculatus. El objetivo del trabajo fue analizar aspectos de la dieta y la reproducción de T. nigromaculatus. Para ello, se realizaron siete muestreos abarcando periodos hidroclimáticos del área de estudio. Los peces fueron capturados empleando una red de arrastre y una atarraya, y las variables fisicoquímicas se midieron in situ. Durante el estudio se analizó el contenido estomacal de 245 ejemplares de T. nigromaculatus a través de métodos numéricos, volumen y frecuencia de ocurrencia. Se calcularon factores como el índice de importancia alimentaria, el coeficiente de vacuidad, la amplitud del nicho trófico, el factor de condición y la sección reproductiva. Asimismo, se determinaron la proporción de sexos,  índice gonadosomático,  fecundidad, tallas mínima y media de madurez sexual y  diámetro de los ovocitos. El río Gaira, considerado mesotrófico con tendencia a la eutrofización, presentó un aumento del  pH y  la conductividad eléctrica del agua. Con respecto a la dieta de T. nigromaculatus, el coeficiente de vacuidad de los ejemplares fue de 13,88 %, y se observó un comportamiento omnívoro con principal consumo de larvas Simulium sp. e insectos. El factor de condición indicó que la especie estuvo bien alimentada. Se identificó una proporción sexual 1:1,5, con 73 machos y 50 hembras. Los machos alcanzaron la talla media de madurez sexual a los 90,46 mm (LE), y las hembras, a los 63,0 mm (LE ).  La relación gonadosomática indicó tres eventos reproductivos, en los que la fecundidad fue menor en bajas lluvias, con 194 ovocitos, y mayor en altas lluvias, con 369. El diámetro del ovocito fue de 0,07 mm en promedio.