This study documents differences in fish assemblages for 32 freshwater streams located between 258 and 2242 m a.s.l. on the eastern slopes of the central range of the Colombian Andes. A total of 2049 fishes belonging to 62 species, 34 genera and 16 families were collected. Species richness declined rapidly with altitude; nearly 90% of the species were recorded between 250 and 1250 m a.s.l. Three of the four physico-chemical variables, of the water, temperature, dissolved oxygen and pH, explained 53.5% of the variation in species richness along the altitudinal gradient, with temperature the most important (37.6%). An analysis of species composition showed that the distinctiveness of the fish fauna increased with elevation, with the greatest turnover observed between 1000 and 1750 m a.s.l. On this altitudinal gradient, turnover was dominated by the loss of species rather than gain, and dominance by just a few species was greater at higher elevations. Turnover was also observed along the altitudinal gradient in the structure of the three functional groups (torrential, pool and pelagic species). The study focused on understanding the pattern of diversity of fish communities inhabiting the Andes in Colombia. Anthropogenic effects on the altitudinal distribution of fish species in the region, however, are largely unknown and would require further investigations.

Studies on elevation diversity gradients have covered a large number of taxa and regions throughout the world; however, studies of freshwater fish are scarce and restricted to examining their changes along a specific gradient. These studies have reported a monotonic decrease in species richness with increasing elevation, but ignore the high taxonomic differentiation of each headwater assemblage that may generate high β-diversity among them. Here, we analyzed how fish assemblages vary with elevation among regional elevation bands, and how these changes are related to four environmental clines and to changes in the distribution, habitat use, and the morphology of fish species. Using a standardized field sampling technique, we assessed three different diversity and two structural assemblage measures across six regional elevation bands located in the northern Andes (Colombia). Each species was assigned to a functional group based on its body shape, habitat use, morphological, and/or behavioral adaptations. Additionally, at each sampling site, we measured four environmental variables. Our analyses showed: (1) After a monotonic decrease in species richness, we detected an increase in richness in the upper part of the gradient; (2) diversity patterns vary depending on the diversity measure used; (3) diversity patterns can be attributed to changes in species distribution and in the richness and proportions of functional groups along the regional elevation gradient; and (4) diversity patterns and changes in functional groups are highly correlated with variations in environmental variables, which also vary with elevation. These results suggest a novel pattern of variation in species richness with elevation: Species richness increases at the headwaters of the northern Andes owing to the cumulative number of endemic species there. This highlights the need for large-scale studies and has important implications for the aquatic conservation of the region.

utilizando assembléias de peixes de água doce, tem sido uma ferramenta efetiva de biomonitoramento amplamente utilizada em países de regiões temperadas. Em países tropicais e subtropicais, no entanto, seu uso é ainda reduzido, apesar da adaptação nestas regiões ter se iniciado há quase 15 anos. Esta revisão inclui 15 adaptações do IIB publicadas para essas regiões. Verifi camos que a maioria delas foi realizada em zonas subtropicais, principalmente em riachos; algumas em rios de maior porte e apenas uma em lagos. Tornou-se evidente a necessidade de uma defi nição clara do local de referência e implementação de metodologias padronizadas e não seletivas (e.g. pesca elétrica), inclusive para rios de grande porte. As métricas foram criadas ou adaptadas usando as famílias ou grupos funcionais que se mostraram sensíveis na região estudada. No entanto, é fundamental que a seleção seja respaldada por métodos estatísticos rigorosos. Apesar do modelo do IIB ter se mostrado efetivo na detecção de alterações ambientais em todos os trabalhos analisados, é evidente que a aplicabilidade e efi cácia nos países tropicais e subtropicais (em geral em desenvolvimento, com grande diversidade e complexidade ecológica) depende do preenchimento das lacunas de informação, tanto sobre diversidade como sobre processos ecológicos. Ressalta-se a importância da participação e coordenação governamental na implantação do biomonitoramento nessas regiões, uma vez que as iniciativas, até o momento, partiram exclusivamente de grupos de pesquisa. Palavras-chave: IIB, índices multimétricos, biomonitoramento, peixes de água doce. ABSTRACT BIOTIC INTEGRITY INDEX USING FRESHWATER FISHES IN TROPICAL AND SUBTROPICAL REGIONS. The Index of Biotic Integrity (IBI) using freshwater fi sh assemblages is an effective biomonitoring tool that is widely used in temperate countries. Despite the fact that the IBI is being adjusted to be applied to studies in tropical and subtropical countries for almost 15 years, it still is rarely used with these regions. The present review visits 15 publications of IBI adaptations for tropical regions. Most studies were performed in subtropical regions and mainly on streams, while some were done in large rivers, and one in lakes. There is evident need for a clear defi nition of the reference condition and for standardized and non-selective methodologies (e.g., electrofi shing), even in large river systems. Metrics were created or adapted using families or functional groups that proved sensitive in the studied regions. However, the metrics must be selected through rigorous statistical methods. Although IBI fi sh models were shown to be effective in detecting environmental changes in all studies analyzed, it is evident that the applicability and effectiveness of these models in tropical and subtropical countries (chiefl y developing countries with high diversity and ecological complexity) depend on fi lling in the informationgaps in diversity and ecological processes. We highlight the importance of government taking part in the coord...

El Concepto de Discontinuidad Serial afirma que la formación de embalses en cadena dentro de los ríos genera cambios en la estructura de la biota acuática que se acumulan a lo largo del cauce. En el río Porce (Cuenca del río Magdalena–Cauca, Colombia) se formaron dos embalses en cadena, los embalses Porce II y Porce III. Para conocer la respuesta del ensamblaje de peces dentro del sector del río que fue embalsado se tomaron muestras de cuatro periodos de lluvias abundantes y cuatro de menores lluvias entre los años 2011 y 2013, en sitios dentro de los dos embalses seleccionados según su posición en el eje longitudinal (cola, transición y presa); para eliminar el efecto de la profundidad en cada sitio se tomaron muestras a dos profundidades (superficial–fondo). Se capturaron 15 especies; 12 en Porce II y 10 en Porce III. Se observaron diferencias espaciales en cuanto a la composición y estructura de especies de peces, tanto en el eje longitudinal (cola–presa), como en el vertical (superficie–fondo). En el embalse Porce II, la riqueza y la abundancia de individuos disminuyeron en dirección cola-presa y fue mayor en la superficie que en el fondo; en el embalse Porce III, aunque la riqueza presentó la misma tendencia en el eje longitudinal, la abundancia fue mayor en el fondo que en la superficie. Las características del ensamblaje no estuvieron asociadas a los periodos pluviométricos en ninguno de los dos embalses. Se concluye que la composición y estructura del ensamblaje está definida por las características morfológicas del embalse, así como la edad y tiempo de retención hidráulica.

No abstract

Se colectaron 355 individuos de Prochilodus magdalenae provenientes de las capturas realizadas por los pescadores artesanales de las ciénagas de Tumaradó, ubicadas en la cuenca baja del río Atrato (Chocó), Colombia, dentro del Parque Nacional Natural Katios. Las colectas se realizaron entre julio y diciembre de 2004, durante el periodo de aguas altas. Las tallas de captura variaron entre 190-380 mm de longitud estándar (LE); aunque no se observaron diferencias significativas entre los meses de muestreo, en el mes de diciembre se registraron los individuos de mayor talla. Las proporciones sexuales mostraron diferencias significativas, predominando las hembras en todos los meses. La abundancia de individuos maduros, la relación gonadosomática, el factor de condición y el coeficiente de alometría evidencian que la época reproductiva de la especie en el bajo Atrato comienza entre diciembre y julio. El número de ovocitos promedio por hembra fue de 52.698; los diámetros presentaron un amplio rango de variación en los meses de muestreo. 22,25% de las capturas se encontraron por debajo de la talla mínima de captura reglamentaria.

Reproducción de los peces en embalses en cascada en un río andino tropical (Colombia) ResumenLa variación de las lluvias y el nivel de los ríos han sido identifi cados como los factores más importantes para la reproducción de los peces de agua dulce en el trópico. Las presas y embalses cambian la infl uencia de estos dos factores, por lo tanto, el ensamblaje debe desarrollar nuevas tácticas para continuar reproduciéndose. Nuestro objetivo fue defi nir los periodos y sitios de reproducción del ensamblaje de peces en la cuenca media del río Porce (Antioquia, Colombia), modifi cado por dos embalses en cascada (embalses Porce II y Porce III). Los muestreos se realizaron entre septiembre de 2011 y diciembre de 2016, durante periodos climáticos contrastantes (lluvias y estiajes), en 31 sitios distribuidos en los embalses de Porc e II y Porce III, en el canal del río (antes del embalse Porce II entre los embalses y después del embalse Porce III) y quebradas tributarias a los dos embalses. Los peces fueron capturados con trasmallo, atarraya y electropesca. Se usó la escala de Vazzoler (1996) para determinar el desarrollo gonadal y se estimó la relación gonadosomática; estos datos se utilizaron para hacer los análisis de la temporalidad reproductiva del ensamblaje de peces, que se defi nió de acuerdo con la intensidad reproductiva (IR) y el porcentaje de ínvidos maduros de las especies. Los resultados mostraron que en los embalses los peces se reproducen intensamente independiente del periodo climático, mientras en las quebradas y el río se observa una tendencia similar, aunque con un incremento de la reproducción asociado con los periodos de estiaje; de manera particular se encontró que la especie Brycon henni tiene un mayor porcentaje de individuos maduros durante los periodos de lluvias en el embalse Porce III y en sus quebradas tributarias. AbstractVariations in rainfall and river level have been identifi ed as the most crucial factors in freshwater fi sh reproduction in the tropics. Dams and reservoirs change the seasonality of these factors, so fi sh must develop new tactics to continue reproducing themselves. Our objective was to defi ne the period and sites of reproduction of fi sh in the middle Porce River drainage, which has been modifi ed by the construction of two reservoirs in cascade (reservoirs Porce II and Porce III). Sampling was carried out from September 2011 to December 2016, during contrasting climatic periods (drought and rains) at 31 sites distributed as follows: in the reservoirs of Porce II and Porce III, in the river channel (above Porce II reservoir, between the reservoirs and below Porce III dam) and tributary streams to two reservoirs. The fi sh were captured with gillnet, seines and electro-fi shing gear. The Vazzoler scale (1996) was used to determine the gonadal development, the gonadosomatic relationship was also estimated and these data were used to make the analysis of the reproductive seasonality of the fi sh assemblage, which was defi ned according to the reproductive intensity (RI) a...