Abstract
The abundance and distribution of ichthyoplankton and their relationships to current velocity, temperature, dissolved oxygen, pH and electrical conductivity of the water in the Anavilhanas Ecological Station, Negro River, Amazonas State, Brazil, were analyzed. Preferred microhabitats for spawning, dispersion and nursery were also verified. Sampling was undertaken during the falling water period of 2001 and the rising water period of 2002, in a section of 100 km subdivided into 5 subsections, with a total of 20 stations (5 beaches, 5 ravines, 5 channels, and 5 lake channels) at night and during the day at the surface and at the bottom. 647 eggs and 4,187 larvae were captured, belonging to 10 families and four orders: Characiformes (6), Siluriformes (2), Perciformes (1), and Clupeiformes (1). Engraulidae (55.39%), Pimelodidae (30.45%), Auchenipteridae (5.23%) and Sciaenidae (5.13%) were the dominant families. The hierarchical statistical model (ANOVA) with three factors (microhabitat, depth and period) was applied to the environmental variables and the larval abundance, showing greater abundances of sciaenids in the ravines and lower abundances of engraulids in the channels. The highest captures were obtained at lower temperature values, at the bottom during the day and at the surface at night, suggesting an active larval behavior. The presence of the four larval development stages in all subsection for pimelodids and sciaenids, and in three subsections for engraulids, indicates that the Anavilhanas Ecological Station is an important spawning and nursery area for species of these groups in the Negro River. Larvae abundance of all characiform families was extremely low (from 0.1 to 1.17%), suggesting that they do not spawn in this system.
Highlights
Fish requires specific areas for reproduction, and recruitment success depends on favorable environmental conditions for the survival of the larvae and juveniles (Urho, 1999)
Many Amazon migratory fish, including commercially important species, spawn in the main channel of the Amazon River and its tributaries (Balon, 1975; Oliveira & AraújoLima, 1998), where the larvae remain for a few days before
According to Araujo-Lima & Oliveira (1998) and Araujo-Lima et al (2001) these are the times of year when the greatest densities of larvae are found drifting in the Central Amazon rivers
Summary
Fish requires specific areas for reproduction, and recruitment success depends on favorable environmental conditions for the survival of the larvae and juveniles (Urho, 1999). Water transportation affects larvae distribution in relation to space and time, and the distribution of food and predators have a positive or negative effect on their survival (Simpson, 1987). Current is the most decisive mechanism in the transportation of larvae to nursery areas (Hergenrader et al, 1982; Pavlov, 1994; Araújo-Lima & Oliveira, 1998; Bialetzki et al, 2004). Dispersion and microhabitats of fish larvae they are carried into the floodplains (Araújo-Lima & Oliveira, 1998). Few studies have considered the microhabitat diversity in rivers with different physicochemical properties
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