Aspects of the reproduction of two sciaenid species, the pescadas Plagioscion squamosissimus HECKEL 1864) and Plagioscion monti (SOARES 1979), Pisces, in different water types of the Central Amazon

Abstract

The pescadas, Plagioscion squamosissimus (HECKEL) and Plagiosscion monti (SOARES), were studied in various kinds of water body in the central Amazon region to determine aspects of their reproduction. In Lago do Janauacá, P. squamosissimus reaches sexual maturity in one year at a mean standard length of 20.5 cm, while in the blackwater Lago Aruaù, the fishes require 1.5 years and average only 19 cm in length. P. monti also becomes sexually mature at an age of one year in Lago do Janauacá, and its average standard length at that time is 18 cm. The main spawning period is at the beginning of the dry season while the water level is decreasing. It was demonstrated that both species spawn repeatedly at regular intervals determinated by the phases of the moon, P. monti biweekly during the the full and new moons and P. squamosissimus monthly during the new moon. From differences in the spawning period, a second population of P. squamosissimus was identified in the blackwaters of Lago Aruaù. It enters the lake from the Rio Branco