ABSTRACT The ichthyofauna of the Río Acahuapa was analyzed sampling 17 sites that included the basin main channel and its tributaries. Fish were collected using dip-nets, seine-nets and electrofishing. Fish standard length and species abundance were recorded. Species origin and salinity tolerance criteria were used to classify fish species. Water physicochemical variables, habitat structure and sampling sites elevation were recorded. A total of 33 fish species were registered, 12.1% are primary, 45.5% are secondary and 42.4% are of marine derivation. Fish species richness declined with increase of elevation (R2=0.55, p=0.0006). Two assemblages of fishes were identified: the first one associated to sites of low elevations (19-184 masl), composed mainly of secondary and marine-estuarine fish species related with high temperature, water velocity, river width, dissolved oxygen and low sand and silt substrate cover; the second one associated to sites of middle and higher elevations (185-519 masl), composed by primary and secondary freshwater fishes related with high pH, logs and rocks substrate cover. In summary, elevation and environmental variables contributed to the composition and distribution of fish in the Río Acahuapa.

RESUMEN La ictiofauna del Río Acahuapa fue analizada en 17 sitios que incluyen el canal principal de la cuenca y sus tributarios. Los peces fueron recolectados utilizando chinchorros, redes de mano y electropesca. Se registró la longitud estándar y la abundancia por especie. El criterio de origen y tolerancia a la salinidad de las especies fue utilizado para clasificar a los peces. Las variables fisicoquímicas del agua, estructura del hábitat y elevación se registraron en cada sitio. Un total de 33 especies fueron registradas, cuyo 12.1% son primarias, 45.5% secundarias y 42.4% son de derivación marina. La riqueza de especies de peces disminuyó con el aumento de la elevación (R2=0.55, p=0.0006). Dos ensamblajes de peces fueron identificados: el primero está asociado con sitios de bajas elevaciones (19-184 msnm), compuesto principalmente de especies de peces secundarias y marino-estuarinas relacionadas con altas temperaturas, velocidad del agua, ancho de río, oxígeno disuelto y baja cobertura de sustrato de arena y limo; el segundo está asociado con sitios de mediana y alta elevación (185-519 msnm), compuesto por peces dulceacuícolas primarios y secundarios relacionados con altos valores de pH y cobertura de sustrato de troncos y rocas. Se determina que la elevación y las variables ambientales contribuyen a la composición y distribución de peces en el Río Acahuapa.

RESUMOO cultivo do milho em sistema de aléias resulta em melhoria do solo, redução das plantas daninhas e aumento do rendimento. Os trabalhos com a cobertura do solo com a parte aérea de árvores produz resultados semelhantes. O objetivo deste trabalho foi avaliar os efeitos da cobertura do solo com 30 t ha-1(matéria fresca) de ramos das espécies arbóreas nim (Azadirachta indica A. Juss), gliricídia [Gliricidia sepium(Jacq.) Kunth ex Walp.], leucena [Leucaena leucocephala (Lam.) de Wit.] e sabiá (Mimosa caesalpiniifolia Benth.) sobre o crescimento das plantas daninhas e sobre o rendimento do milho. Dois grupos de tratamentos (cultivares e controle de plantas daninhas) foram avaliados. As cultivares AG 1041 e AL Bandeirantes foram submetidas aos seguintes tratamentos: sem capinas, duas capinas e cobertura do solo, por ocasião da semeadura do milho, com ramos das espécies referidas. Utilizou-se o delineamento de blocos casualizados com parcelas subdivididas (cultivares nas parcelas) e dez repetições. As cultivares não diferiram quantos aos rendimentos de espigas verdes e de grãos. A realização de duas capinas foi mais eficiente na redução do crescimento das plantas daninhas do que a cobertura do solo. Entretanto, as capinas e a cobertura do solo propiciaram rendimentos semelhantes de espigas verdes e de grãos, que foram superiores aos obtidos no milho não capinado.

ABSTRACTCultivating maize under systems of alley cropping results in improvements to the soil, a reduction in weeds and an increase in yield. Studies using ground cover from tree shoots produce similar results. The aim of this study was to evaluate the effects on weed growth and maize yield of ground cover made up of 30 t ha-1 (fresh matter) of branches from the tree species: neem (Azadirachta indica A. Juss), gliricidia [Gliricidia sepium(Jacq.) Kunth ex Walp.], leucaena [Leucaena leucocephala (Lam.) de Wit.] and sabiá (Mimosa caesalpiniifolia Benth.). Two treatment groups (cultivars and weed control) were evaluated. The cultivars AG 1041 and AL Bandeirantes were subjected to the following treatments: no hoeing, double hoeing, and ground a cover of branches of the above species when sowing the maize. A randomised block design was used with split lots (cultivars in the lots) and ten replications. The cultivars did not differ for green ear or grain yield. Double hoeing was more effective than ground cover at reducing the growth of weeds. However, both weeding and ground cover resulted in similar yields for green ears and grain, which were greater than those obtained with the unweeded maize.