Resumen Una de las causas que aportan a la disminución de la biodiversidad es la introducción de especies exóticas que muchas veces terminan siendo invasoras, y por lo tanto terminan compitiendo con especies locales. Esta competencia no siempre es equitativa ya que las especies invasoras comúnmente cuentan con ventajas adaptativas que le otorgan beneficios ante las especies locales. Este estudio realizado en microcuencas del noroccidente del Ecuador identifica los efectos de la reciente presencia de Poecilia gillii sobre la especie nativa Pseudopoecilia fria; mediante un análisis poblacional (distribución longitudinal, parámetros de crecimiento y morfometría). Los resultados muestran un desplazamiento de P. fria hacia la parte alta del río, un aceleramiento en su crecimiento y por lo tanto una madurez anticipada con la consecuente disminución del tamaño corporal y finalmente un cambio en el alto del cuerpo con deslizamiento posterior de la aleta pectoral.

Abstract One of the causes contributing to the decrease of biodiversity is the introduction of exotic species that often end up being invasive, and end up competing with local species. This competition is not always “fair” since invaders commonly have adaptive advantages that give them an advantage over local species. This study was carried out in small watersheds in northwestern Ecuador and identifies the effects of the recent introduction of P. gillii on the native species P. fria; using population analysis (longitudinal distribution, growth parameters and morphometry). The results show a displacement of P. fria towards the upper part of the river, acceleration in its growth and therefore an earlier sexual maturity with a consequent decrease in body size and finally a change in body depth with posterior displacement of the pectoral fin.

La mayoría de los ríos en las montañas andinas de Venezuela en la cuenca del Orinoco sufren variadas perturbaciones. A pesar de esto, sus comunidades de peces han sido poco evaluadas en términos de sus gradientes espaciales y temporales. La generación de información sobre estas comunidades es prioritaria, y puede impulsar la conservación de los recursos hidrobiológicos regionales. Con este fin, seis localidades fueron evaluadas mensualmente en tributarios de la cuenca alta del río Turbio en la Sierra de Portuguesa (770-1 305msnm) durante el período de sequía y el inicio del período de lluvias (enero-abril de 2012), se caracterizaron las dimensiones del cauce, el sustrato y las variables físico-químicas del agua. Se utilizó electropesca para determinar el número y abundancia de especies de peces. Las comunidades de peces y su estabilidad se evaluaron explorando los cambios en la riqueza y abundancia y por coeficientes de variación, clasificación jerárquica y análisis de escalamiento multidimensional no métrico. El estado de conservación de las localidades se estimó con un índice de integridad del hábitat. La riqueza de 12 especies varió según la elevación, los tributarios y el estado de conservación de las localidades. Chaetostoma dorsale, Creagrutus taphorni y Chaetostoma milesi comprendieron el 90.8% de la abundancia relativa y mantuvieron los primeros rangos durante el período. Las comunidades tuvieron poca variación espacio-temporal y esta se expresó en un gradiente asociado principalmente por las coberturas de sombra, rocas y grava, la temperatura del agua y la conductividad. La estabilidad fue moderada, variando con la elevación y el estado de conservación de las localidades. Los tributarios en la cuenca alta del río Turbio se encuentran bajo impactos severos y sus ictiofaunas son empobrecidas y en situación de riesgo.

Most Andean mountain streams of the Orinoco Basin in Venezuela, had been suffering various disturbances. in spite of this, fish communities have been poorly evaluated in terms of spatial and temporal gradients. Thus, the generation of information about these communities is a priority, since it may support conservation of regional hydrobiological resources. For this, six sites were monthly evaluated in tributaries of upper Turbio River in Sierra de Portuguesa (770-1 305msnm), during the dry season and the beginning of the rainy season (January-April 2012); we characterized stream dimensions, substrate and water physicochemical variables. Electrofishing was used to determine the number and abundance of fish species. The fish communities and their stability were evaluated by exploring the changes in richness and abundance, coefficients of variation, hierarchical classification and non-metrical multidimensional scaling analysis. The sites conservation status was estimated with a habitat integrity index. Our results showed that richness of the 12 species found varied according to the mountain elevation, the tributaries and the conservation status of the sites. Chaetostoma dorsale, Creagrutus taphorni and Chaetostoma milesi comprised 90.8% of the relative abundance, and maintained the first ranks during the study period. The communities had little spatio-temporal variation which was associated with a gradient signed principally by the amount of shadow, rocks and gravel cover, water temperature and conductivity. Stability was moderate but varied with elevation and according to site conservation status. The tributaries in upper Turbio River were found to be under severe impacts and their fishes were found impoverished and at risk.

Aquí se presenta una clave taxonómica para la identificación de cinco especies de peces del genero Creagrutus de las cuencas de los ríos Yaracuy, Urama, Aroa, Tocuyo, Remedios, Hueque y Ricoa de la vertiente Caribe en la región Centroccidental de Venezuela.

This text presents a taxonomic key for the identification of five species of fish of the genus Creagrutus for the basins of the Yaracuy, Urama, Aroa, Tocuyo, Remedios, Hueque and Ricoa rivers of Venezuela's Midwestern Caribbean basin.

Foram avaliados o ambiente físico e as assembléias de peixes em rios das montanhas Aroa (Venezuela) com diferentes níveis de proteção ambiental devido a criação do Parque Nacional Yurubí nesta drenagem. Foi desenvolvido um Índice de Integridade Biótica (IBI), avaliado através da análise de componentes principais (PCA) e análise de correspondência canônica (CCA). Rios tributários foram divididos em classes, de acordo com sua origem (proteção pelo Parque) e características físicas, incluindo o substrato. Peixes foram capturados utilizando-se pesca-elétrica padronizada. As comunidades de peixes mostraram maior riqueza de espécies em habitats heterogêneos e rios protegidos, porém a abundância foi maior em áreas não protegidas e rios não impactados. O IBI foi sensível a estas diferenças e os escores foram mais elevados em rios protegidos. O IBI detectou o grau de distúrbio nas comunidades de peixes sem a consiedração direta dos parâmetros de habitat medidos. O PCA revelou um gradiente de heterogeneidade no substrato. De modo similar, a CCA revelou diferenças na composição da assembélia de peixes ao longo do gradiente ambiental que variou com o estatus de proteção do rio. A relação entre os escores de PCA e IBI foi altamente significativa (r² = 0.61, P < 0.0001). As análises de PCA e CCA validaram moderadamente a estrutura e a previsibilidade do IBI; porém, é necessário refinar o modelo e estender este aplicativo por mais tempo e área mais abrangente.

We examined physical habitat and fish assemblages in rivers of the Aroa Mountains (Venezuela) with different levels of environmental protection due to the creation of Yurubí National Park within the drainage. We developed an Index of Biotic Integrity (IBI) and evaluated it using principal components analysis (PCA) and canonical correspondence analysis (CCA). Tributary rivers were divided into classes according to their origin (protected by the park) and physical characteristics of each, including substrate. Fishes were captured using standardized electrofishing. Fish communities showed greater species richness in heterogeneous habitat and protected rivers but overall abundance was higher in unprotected and impacted rivers. The IBI was sensitive to these differences and the scores were higher in protected rivers. The IBI detected degree of disturbance of fish communities without direct consideration of habitat parameters measured. The PCA revealed a gradient in substrate heterogeneity. Similarly, CCA revealed differences in fish assemblage composition along the environmental gradient and that varied with protection status of the river. The relationship between PCA and IBI scores was highly significant (r² = 0.61, P < 0.0001). The PCA and CCA analysis moderately validated the structure and predictability of IBI; but it is still necessary to refine the model and to extend its application for more time and over a wider area.

Para obter informações básicas para o manejo de Salminus sp. no sopé andino ocidental da Venezuela, se estudaram aspectos sobre sua ecologia e aproveitamento. Nos rios do sopé da montanha efetuaram-se capturas de peixes com variados tamanhos de malha, assim como observações subaquáticas e terrestres para estimar abundâncias e eventos de alimentação. Aplicaramse entrevistas para recolher dados sobre seu aproveitamento. A espécieé representada em toda a região, seus indivíduos são pouco frequentes e formam cardumes, sendo mixtos com exemplares de Brycon whitei quando os primeros são de tamanho pequeno. A abundância média foi maior nos rios de tamanho grande e não variou de maneira importante no tempo para todos os rios. Os tamanhos e pesos estiveram entre 15,1 e 40,5 cm de comprimento padrão (CP) e entre 47,7 e 1.210 g, respectivamente. As fêmeas tiveram máxima maturação gonadal no começo do período de chuvas, com fecundidade média de 35.834 ovos e eventos reprodutivos em momentos de subida dos ríos. Os eventos de alimentação foram mais frequentes nas primeiras eúltimas horas de luz solar. Em peixes menores de 20 cm de CP, a dieta da espécie foi variada, mas acima deste tamanho os peixes foram o item principal na dieta. Salminus sp. tem pouca importância comercial mas forma parte da pesca de subsistência e eventualmenteé objeto da pesca esportiva. O tamanho legal mínimo de captura para a espécie deve ser revisado, visto que permite o aproveitamento de indivíduos imaturos sexualmente.

To obtain basic information for management, aspects of the ecology of Salminus sp. (Pisces: Characidae), were studied in piedmont rivers of the southwestern flank of the Andes in Venezuela. Collections were made with seines of various lengths and mesh sizes, and both underwater and terrestrial observations were recorded to estimate abundance and feeding events. Interviews with local fishermen and inhabitants were made to obtain data on use. The species is present along the entire length of the Andean piedmont in Venezuela, although in some rivers it is now scarce. Small individuals form mixed schools with Brycon whitei, but larger Salminus sp. usually only school with others of the same species. Average abundance was greater in larger rivers, and didn't vary appreciably with season for any of the rivers studied. Size and weight ranged from 15.1 to 40.5 cm SL and 47.7 to 1,210 g, respectively. Females had maximum ovary maturity at the beginning of the rainy season, with an average fecundity of 35,834 eggs, and spawning occurred during spates of high water. Feeding was crepuscular, with most events recorded during the first and last hours of sunlight. In smaller fish up to 20 cm SL, the diet was varied, but above that size fish were the principal food item. Salminus sp. has little commercial importance in this region but forms an important part of the local subsistence fishery, and occasionally it is targeted for sport fishing. The minimum legal size of capture for the species should be raised, since the current limit permits the capture of many sexually immature individuals.

Se reporta la reproducción de peces en eventos de crecidas del río Portuguesa, Venezuela. En los llanos altos (alrededor de 100 msnm) y sólo en velocidades específicas de crecida (mayores de 0,59 m/s) fueron colectados huevos de peces que presentaron estadios embrionarios entre el cuarto clivaje y la fase de movimiento autónomo del embrión, sugiriendo que los eventos reproductivos se sucedieron en un tramo específico de río asociado a la transición geomorfológica del piedemonte con los llanos altos. Estos huevos se colocaron en incubadoras donde se obtuvo una gran mayoría de especies de peces Characiformes y Siluriformes, los cuales son reconocidos como migratorios que realizan movimientos locales de ascenso y descenso en el momento de crecidas. Se consideran dos aspectos básicos en la reproducción de los peces en las crecidas: magnitud del caudal y áreas de inundación aguas abajo. Los ecosistemas fluviales regionales se encuentran sometidos a severos impactos (represas, deforestación) que afectan la supervivencia de gran parte de la ictiofauna que se reproduce en eventos de crecidas. Se sugiere un manejo especial del tramo del río Portuguesa en donde ocurren los eventos reproductivos.

The reproduction of fishes in flooding events in the Portuguesa River, Venezuela, is reported. In the high plainlands (about 100 meter above sea level) and only at specific water speeds (higher than 0.59 m/s) eggs presenting embryonic stages between the four-cell-embryo and the phase of independent movement of the embryo were collected, suggesting that reproductive events occurred in a specific section of river associated to the geomorphological transition from foothills to the high plainlands. The eggs were incubated in laboratory and it was obtained mainly species of Characiformes and Siluriformes which are migratory fishes that make local movements of ascent and descent at the time of flooding. Two basic aspects in the reproduction of fishes during floods are considered: magnitude of the water flow and areas of flood downstream. The regional fluvial ecosystems are put under severe impacts (dams, deforestation) that affect the survival of great part of ichthyofauna that reproduces during events of flooding. A special management of the section of the Portuguesa River is suggested where the reproductive events take place.