Néstor Javier Mancera-Rodríguez

Freshwater fish faunas, habitats and conservation challenges in the Caribbean river basins of north-western South America

The remarkable fish diversity in the Caribbean rivers of north-western South America evolved under the influences of the dramatic environmental changes of neogene northern South America, including the Quechua Orogeny and Pleistocene climate oscillations. Although this region is not the richest in South America, endemism is very high. Fish assemblage structure is unique to each of the four aquatic systems identified (rivers, streams, floodplain lakes and reservoirs) and community dynamics are highly synchronized with the mono-modal or bi-modal flooding pulse of the rainy seasons. The highly seasonal multispecies fishery is based on migratory species. Freshwater fish conservation is a challenge for Colombian environmental institutions because the Caribbean trans-Andean basins are the focus of the economic development of Colombian society, so management measures must be directed to protect aquatic habitat and their connectivity. These two management strategies are the only way for helping fish species conservation and sustainable fisheries.

The role of the hydrological cycle on the distribution patterns of fish assemblages in an Andean stream.

The seasonal and interannual changes of the fish assemblage in the main channel and littoral zone of the Guarinó River, a torrential system located in the Colombian Andean foothills, were examined in relation to the physical and chemical environmental changes associated with the hydrological cycle and the El Niño-La Niña-Southern Oscillation (ENSO) between 2007 and 2010. Four samplings per year (in dry season and high water) were performed. Environmental variables (temperature, pH, conductivity, turbidity, oxygen, total nitrogen, orthophosphate, depth and flow rate) were contrasted with ANOVAs and a discriminant analysis to establish temporal patterns. Biological descriptors (richness, density and biomass) were contrasted with ANCOVAs. The temporal patterns of the taxonomic and functional composition and the density of the fish assemblages were examined with respect to environmental variables through canonical discriminant analysis per habitat. Interannual differences were significant with regard to density and richness for the main channel habitat; while in the littoral zone, the differences were significant between both the year and seasons. Discriminant analysis showed variations in species composition and relative abundance between the main channel and the littoral zone under contrasting hydrological conditions of El Niño-La Niña. High flows from 2008 to 2009 (La Niña) favoured resident species (e.g. Creagrutus magdalenae) and small benthic Siluriformes (e.g. Chaetostoma spp.), but was limited to migratory species (e.g. Prochilodus magdalenae). From 2009 to 2010 (El Niño), the most common species were reduced and rare species increased. River flow, temperature and oxygen were the variables that had the largest influences on the seasonal and interannual differences in the fish assemblage structure of the Guarinó River. The results suggested that the presence and abundance of species and functional groups in different habitats were regulated by stochastic conditions, such as droughts, floods and drag events associated with the Southern Oscillation phenomenon (ENSO), acting as a hydrological disturbance on the habitats and generating different responses according to the adaptive characteristics of the species.

Variations of body geometry in Brycon henni (Teleostei: Characiformes, Bryconidae) in different rivers and streams

Landmark-based geometric morphometrics were used to evaluate the effect of flow and depth in the water column on the body size and shape of Brycon henni from river and stream populations. The dendrogram showed that stream populations clustered apart and showed significantly smaller centroid size and narrower bodies than river populations, indicating a role for flow and depth on whole body morphometric variation. The results are concordant with morphometric variation described in other fish species and provide the first insights into phenotypic variation in natural populations of B. henni.

Molecular and morphometric characterization of two dental morphs of Saccodon dariensis (Parodontidae).

This study reports for the first time the roles of genetic and body phenotypic variation in two Saccodon dariensis dental morphs. Results showed a lack of ancient mitochondrial differentiation between morphs and body variations concordant with genetic polymorphism or differential plastic responses to diet quality and foraging strategies of S. dariensis.

Efectos de la deforestación sobre la diversidad y la estructura del ensamblaje de macroinvertebrados en cuatro quebradas Andinas en Colombia

Effects of deforestation on macroinvertebrate diversity and assemblage structure in four Andean creeks in Colombia. The creeks are strongly influenced by their riparian vegetation, and the deforestation affect the aquatic community. The effects of deforestation on taxonomic and functional diversity of aquatic macroinvertebrate assemblage in four Colombian Andean creeks were evaluated. The study included 12 sites, seven of them with arboreal coverage at their margins in forested areas undisturbed by deforestation (reference stations) and the other five without tree cover in deforested areas (altered stations). Four field samplings were carried out between June 2011 and February 2012, and samples of benthic macroinvertebrates were collected using the D-net method with 500 μm mesh and manual collection, and different physicochemical variables were measured in situ. The Shannon-Wienner (H′) and Simpson ́s index (D) were calculated. One-way analyses of variance (ANOVAs) to each environmental variable, and canonical discriminant analysis (CDA) to establish differences in environmental variables, taxonomic and functional diversity between references and altered stations were applied. 8 370 macroinvertebrate individuals corresponding to 80 taxa were collected in the study, with 6 758 individuals and 75 taxa in references stations and 1 612 individuals and 50 taxa in altered stations. The reference stations had higher values of diversity and the taxa that made major contributions to the variance between reference and altered stations were Thraulodes, Anacroneuria and Rhagovelia, which were associated with the highest values of Index of Andean riparian vegetation Quality (QBR-And), fluvial habitat index (IHF), Biological Monitoring Working Party Colombia BMWP/Col, EPT index (Ephemeroptera, Plecoptera, and Trichoptera) and temperature in reference stations, whereas Leptonema, Baetodes and Mayobaetis were associated with higher pH and elevation above sea level in altered stations. The main functional feeding groups (FFG) at the reference stations were collectors-gatherers/scrapers CG / SC (27.2 %), scrapers SC (25.4 %) and predators PR (24.4 %), and for altered stations were collectors-filterers CF (27.5 %), collectors-gatherers/scrapers CG / SC (17.4 %) and scrapers SC (15.7 %). The most abundant life habits were clingers Cg (50.5 %), taxa with three or more habits (28.7 %) and skaters Sk (16.1 %), in the reference stations, and clingers Cg (68.1 %), taxa with three or more habits (13.7 %) and burrowers Bu (5.2 %) in the altered stations. The knowledge of the variables that determine the taxonomic and functional structure of the macroinvertebrate assemblages, and how they respond to impacts such as deforestation, can help to determine actions of protection or restoration of the environmental and ecological conditions of the Andean streams and the riparian habitats.

Feeding ecology of the planehead filefish Stephanolepis hispidus (Pisces: Monacanthidae), in the Canary Islands area

Se examino la ecologia alimentaria de Stephanolepis hispidus, en aguas de las Islas Canarias. El estudio se baso en el contenido estomacal de 823 ejemplares de 8,9 cm a 25,9 cm de longitud total (LT), capturados mensualmente en trampas para peces entre febrero de 1998 y junio de 1999. Aproximadamente el 27,2% de los peces mostraron estomagos vacios. Esta proporcion vario significativamente entre los sexos, pero no entre las clases de tamano o las estaciones evaluadas. La dieta de Stephanolepis hispidus se compone principalmente por hidrozoos, anfipodos, equinodermos y algas. Gastropodos, decapodos y lamelibranquios fueron presas secundarias. De acuerdo con el cambio de la ontogenia, los individuos de pequeno tamano (<12,9 cm LT) se alimentan principalmente de pequenos crustaceos (anfipodos e hidrozoos), mientras que los especimenes de gran tamano consumen equinoideos, algas, crustaceos y lamelibranquios. Hidrozoos y algas son mas importantes en la dieta durante la primavera, y los anfipodos fueron mas importantes en invierno. Los erizos de mar aumentan en verano y otono. Los valores del indice de Morisita indicaron superposicion de la dieta entre individuos de las clases de tallas mas pequenas y mas grande que 12,9 cm LT (S= 0,77). Asimismo, la variacion estacional en la superposicion de la dieta fue alta durante invierno (S= 0,95) y primavera (S= 0,93), pero fue relativamente menor en otono (S= 0,68). Los resultados indicaron que la alimentacion de la especie abarca un estrecho rango de presas con algun grado de selectividad y se compone principalmente por macroinvertebrados.