Diel variation of larval fish abundance in the Amazon and Rio Negro

Abstract

Many streams and large rivers present higher ichthyoplankton densities at night. However, in some rivers this does not occur and larvae are equally abundant during the day. Larval drift diel variation is an important information for planning sampling programs for evaluating larval distribution and production. The aim of this study was to test whether the abundance of larval fish was different at either period. We tested it by comparing day and night densities of characiform, clupeiform and siluriform larvae during five years in the Amazon and one year in Rio Negro. We found that larvae of three species of characiform and larvae of siluriform were equally abundant during day and night in the Amazon. Conversely, the catch of Pellona spp. larvae was significantly higher during the day. In Rio Negro, however, larval abundance was higher during the night. These results imply that day samplings estimate adequately the abundance of these characiform and siluriform larvae in the Amazon, but not Pellona larvae. Evaluations of larved densities of Rio Negro will have to consider night sampling.

Spawning areas, dispersion and microhabitats of fish larvae in the Anavilhanas Ecological Station, rio Negro, Amazonas State, Brazil

“…These results are similar to many others of diurnal distribution and abundance of ichthyoplankton in tropical rivers (Baumgartner et al, 1997;Araújo-Lima et al, 2001;Bialetzki et al, 2004) and in temperate regions (Gale & Mohr, 1978;Hergenrader et al, 1982;Gallagher & Conner, 1983;Corbet & Powles, 1986;Gadomski & Barfoot, 1998). Baumgartner et al (2004) studying larvae of Hypophthalmus edentatus, Plagioscion squamosissimus and species of Characiformes in the upper Paraná River mentioned the interaction of several factors that act in the highest capture at the surface at night, but they affirm that the feeding activity would trigger the whole process of vertical distribution.…”

“…Baumgartner et al (2004) studying larvae of Hypophthalmus edentatus, Plagioscion squamosissimus and species of Characiformes in the upper Paraná River mentioned the interaction of several factors that act in the highest capture at the surface at night, but they affirm that the feeding activity would trigger the whole process of vertical distribution. Possible explanations for the differences between day and night catches in the Negro River might be related to larval vision, especially for the more developed and visually active ones (Katsuragawa & Matsuura, 1990;Araújo-Lima et al, 2001). In this study 87.12% of the larvae caught were in larval vitelline and preflexion stages, with standard length between 2.0 and 6.8 mm, with initial ontogenetic development.…”

“…Evaluation of larval density depends on the drift pattern of the larvae, which is influenced by photoperiod, current speed in the microhabitats, sampling depth, and investigated species (Pavlov, 1994;Gadomski & Barfoot, 1998;Araújo-Lima et al, 2001). Considering these aspects, black water rivers of the Amazon basin, with its low-nutrient content, are very different from the whitewater rivers (Goulding et al, 1988;Walker, 1990) and poorly studied (Oliveira & Ferreira, 2002).…”

Analysis of fish eggs and larvae flowing into the Three Gorges Reservoir on the Yangtze River, China

“…Water transparency profoundly affects the photoperiod [25], so will also affect the daily drift pattern of eggs and larvae [26]. As reported by Araujo-Lima, there were no distinct diel variations in larvae drift density when the water transparency was low [27].…”

Reproducción, Crecimiento y Tasa de Explotación de Chiochio (Psectrogaster rutiloides) en la Cuenca del Río Ucayali entre 2008-2012

“…La amplitud del periodo reproductivo es variable y oscila generalmente de octubre a febrero (incluso marzo en 2011), lo que equivale a decir que la especie se reproduce en la época de transición a creciente, prolongándose hasta mediados de la crecienFigura 1. Patrón mensual de precipitación (1) , caudal (2) y nivel promedio del río Ucayali Los valores del IGS definen, para Ucayali, al mes de noviembre como el pico de desove (Figura 3), corroborándose lo observado en el análisis de la progresión de los estadios de madurez. Se puede considerar que la ocurrencia del desove durante esta época constituye un mecanismo de adaptación a la presión selectiva del medio ambiente, con la finalidad que la progenie, que se dispersa por migración pasiva hacia zonas inundadas durante los pulsos de inundación, aproveche las La proporción por sexos mostró diferencias significativas (p<0.05), de acuerdo a la prueba de contraste de X 2 , de la proporción teórica 1H:1M en 26 de los 43 meses con registro de información (Figura 4).…”