Fatores influenciando a estrutura e distribuição espacial dos peixes nos Igarapés de cabeceira do Parque Nacional do Jaú, Amazônia Central

The aim of this study was to investigate the influence of spatial variation in river channels and habitats on the distribution of fish communities in the headwater streams of the Jaú River System, a blackwater tributary of the Negro River. Collections and measurements were made in 34 headwater streams during the period of November-December, 1998. Fish were captured with fish traps and hand nets along standard reaches of two meanders. Data on benthic habitat structure, stream depth and width were collected along lateral transects in each sample reach. A total of 66 fish species from 24 families were collected and classified into seven trophic guilds: allocthonous insectivore, autochthonous insectivore, general insectivore, piscivore, detritivorous planktivore, detritivorous insectivore and insectivorous piscivore. Variations in the distribution and diversity of bottom substrates were important factors influencing fish community structures in these systems. Also, variation in stream size explained the observed variability in fish communities. © 2014, Instituto Internacional de Ecologia. All right reserved

Body shape, diet and ontogenetic diet shifts in young fish of the Sinnamary river, French Guiana, South America

A total of 1468 young fish representing 66 taxa from the Sinnamary river, French Guiana was classified by complete cluster analysis of mean relative body width and mean relative body height into four groups. These had anguilliform, disciform, flat or intermediate body shapes and belonged chiefly to Gymnotiformes, Perciformes, Siluriformes and Characiformes, respectively. Several of the taxa shifted from one to another body shape during ontogenesis. Seven diet groups were defined by complete cluster analysis. Among these, six groups were represented by carnivorous fish. The three most frequent groups had diets of mainly insect larvae and small crustaceans, insect larvae, and predominantly terrestrial insects. The majority of the fish taxa showed ontogenetic diet shifts. Carnivorous fish usually switched from small-size prey, such as insects and/or fish. However, taxa differed in their capacities to switch from small prey to intermediate and/or to large prey. Taxa of different body shapes had significantly different diets. Disciform fish fed mainly on aquatic insect larvae and terrestrial insects but also, in small amounts, on small crustaceans. Most anguiliform taxa ate insect larvae. Individuals belonging to the depressiform or intermediate morphotype had varied diets ranging from plant debris and substratum to fish. (Résumé d'auteur