<b>Estrutura populacional de peixes no estuário do rio Caeté, Bragança, Pará, Brasil</b> - DOI: 10.4025/actascibiolsci.v20i0.4469

Abstract

This study describes the relative size and age structure of the sciaenids Macrodon ancylodon, Stellifer rastrifer and Stellifer naso, the ariid Cathorops spixii and the aspredinid Aspredo aspredo in the estuary of the Caeté River. Four bimonthly samples were collected with trawl and gill nets during August, October and December 1996 and February 1997 in three different areas: (A) main river channel, (B) bay, and (C) coastal areas. Total length and weight of 16,298 individuals of all these species were recorded. Monthly frequency distributions were plotted. Cohorts were identified by dividing the distribution into separate normal distributions; asymptotic length (L_∞) and K were estimated for these stocks by FISAT program. Biomass averages (g/m²) were estimated using the swept area method. Average biomass of Macrodon ancylodon was 0.29g/m², total length ranged from 3cm to 41cm; length frequencies identified five cohorts; L_∞ = 45.50cm and K = 0.491 year^-1. For Stellifer rastrifer, average biomass was 0.31 g/m²; total lengths ranged from 1 to 17cm; L_∞ = 22.5cm and K = 0.31 year^-1. For Stellifer naso, average biomass was 0.03 g/m² ; L_∞ = 26.3cm and K = 0.321 year^-1, total lengths ranged from 2 to 25cm. For Cathorops spixii, average biomass was 0.55 g/m²; L_∞ = 33.3cm and K = 0,36 year^-1; density was much higher in the river habitats. Aspredo aspredo presented a biomass of 0.06 g/m²; abundance was higher in the river; total lengths ranged from 2 to 36cm; L_∞ = 42.5cm and K = 0.35 year^-1. Despite the different biological strategies of each species with respect to spatial distribution and relative abundance, they all utilize the estuarine habitat as nursery grounds in the early phases of their life cycles.