Population biology of torroto grunt, Genyatremus luteus (Bloch, 1790), brazilian amazonian coast

Abstract

Genyatremus luteus is a species of commercial importance in the Pará state. In this study, the population biology of G. luteus was investigated in an estuary of the Eastern Amazon, the collections occurred from October 2012 to October 2013, each month, in the tidal channel (Furo grande), with block net. In the laboratory, the individuals were gauged in relation to the lengths: total, standard, head and height, in addition to weight being recorded. After ventral incision and gonads removal, the gonadal stage was defined for females and males macroscopically. A total of 460 individuals were captured, whose sizes and weights ranged from 4.50 to 21.40 cm and 1.36 and 148.26 g. The relative frequencies of females and males were different than the expected 1:1 (X²: 8.90, p < 0.01), differing significantly by sex and size class (p < 0.01). The mean size (CT) presented significant differences in relation to sex (F = 22.71, p < 0.01), month (F = 35.80, p < 0.01) (P <0.01), gonadal stage (F = 29.77, p <0.01) and gonadal stage by seasonal period (F = 2.37, p < 0.05). The wet weight did not differ statistically by gonadal stage, seasonal period and sex. The ordering diagram showed that the turbidity was the variable that responded by the greater variability in the data (total of 97%). The specimens captured in this study are small in size and weight and reproductively immature, with higher occurrence of females and in greater numbers in the dry period.