Morfometria e crescimento da pescada-branca Plagioscion squamosissimus (HECKEL, 1840) no reservatório da UHE de Tucuruí, Amazônia Oriental.

Abstract

Studies on morphometry and growth are fundamental to understanding organism development and to supporting the adequate management of fisheries resources. This study aimed to analyse the morphometry and estimate the growth of the South American silver croaker, Plagioscion squamosissimus, in the Tucuruí reservoir, considering the environmental changes brought about by the damming of the Tocantins River. A total of 355 individuals were sampled over five campaigns conducted between December 2017 and January 2019; of these, 353 were included in the morphometric analyses, while the 355 specimens with valid total length and date records were used in the length-frequency analysis. Linear morphometric relationships and the length– weight relationship were analysed by area and by sex, and possible spatial size stratification was investigated through principal component analysis (PCA), redundancy analysis (RDA), and permutational multivariate analysis of variance (PERMANOVA); von Bertalanffy growth parameters were estimated indirectly and exploratorily, with all individuals pooled, using Electronic Length Frequency Analysis (ELEFAN). Allometric growth was predominantly isometric across all areas and sex groups, with significant positive allometry in both males and females in Area 2, and significant differences in body size distribution were detected among the sampled strata, partially associated with the environmental variables assessed; as the sectors were sampled in distinct periods, the spatial and temporal components could not be fully disentangled. The indirect growth estimate indicated an asymptotic length of 62.06 cm (620.6 mm) and a growth coefficient of 0.064 year⁻¹, a preliminary result given the reduced number of sampling dates available, which requires validation through independent methods. As the specimens were obtained using gillnets of different mesh sizes, the length-frequency data used in the growth estimate represent, finally, the fraction of the population vulnerable to the gear employed.

Studies on morphometry and growth are fundamental to understanding organism development and to supporting the adequate management of fisheries resources. This study aimed to analyse the morphometry and estimate the growth of the South American silver croaker, Plagioscion squamosissimus, in the Tucuruí reservoir, considering the environmental changes brought about by the damming of the Tocantins River. A total of 355 individuals were sampled over five campaigns conducted between December 2017 and January 2019; of these, 353 were included in the morphometric analyses, while the 355 specimens with valid total length and date records were used in the length-frequency analysis. Linear morphometric relationships and the length– weight relationship were analysed by area and by sex, and possible spatial size stratification was investigated through principal component analysis (PCA), redundancy analysis (RDA), and permutational multivariate analysis of variance (PERMANOVA); von Bertalanffy growth parameters were estimated indirectly and exploratorily, with all individuals pooled, using Electronic Length Frequency Analysis (ELEFAN). Allometric growth was predominantly isometric across all areas and sex groups, with significant positive allometry in both males and females in Area 2, and significant differences in body size distribution were detected among the sampled strata, partially associated with the environmental variables assessed; as the sectors were sampled in distinct periods, the spatial and temporal components could not be fully disentangled. The indirect growth estimate indicated an asymptotic length of 62.06 cm (620.6 mm) and a growth coefficient of 0.064 year⁻¹, a preliminary result given the reduced number of sampling dates available, which requires validation through independent methods. As the specimens were obtained using gillnets of different mesh sizes, the length-frequency data used in the growth estimate represent, finally, the fraction of the population vulnerable to the gear employed.