Inferences about Fishing Impacts on the Reproductive Pattern of Torroto Grunt-Genyatremus luteus (BLOCH, 1790)-From the Amazon Continental Shelf

Genyatremus luteus' reproductive dynamics were investigated by examining the gonadal first maturation length (L-50) and reproductive period (gonadosomatic index, GSI, and relative condition factor, Kr) in relation to the environmental factor rainfall. Sampling was conducted monthly from April 2016 to April 2017, in five areas (A1 to A5) using gill nets and fixed traps. The sex ratio distribution of the 331 specimens captured (174 females, 140 males, and 17 with undetermined sex) did not differ between months. Females were larger (19.28 cm vs. 16.63 cm to males) and heavier (147.21 g vs. 92.14 g to males) and, for both sexes, the means of Kr and GSI indicated the probable spawning period of the species that occurred from June to September, after a decrease in the precipitation of the region. The value of L-50 was estimated as 15.13 cm for females, 14.29 cm for males, and 14.78 cm for both sexes. In the rainy season, the behavior of the species is associated with breeding in certain areas but in the dry season, it is related to the fattening and refuge of juveniles and adults. This research shows the first insight for fishing management about a species that requires different ecosystems to complete their life cycle.

Automated summary

The reproductive dynamics of Genyatremus luteus were studied, particularly the factors of first maturation length (L-50) and reproductive period (gonadosomatic index, GSI, and relative condition factor, Kr), which were found to be influenced by rainfall. Monthly sampling in five areas (A1 to A5) from April 2016 to April 2017 using gill nets and fixed traps resulted in the capture of 331 specimens, with no significant difference in sex ratio distribution between months. Females were larger and heavier than males, and the means of Kr and GSI suggested a spawning period from June to September after a decrease in regional precipitation. The L-50 values were estimated as 15.13 cm for females, 14.29 cm for males, and 14.78 cm for both sexes. During the rainy season, the species exhibited breeding behavior in certain areas, while in the dry season, it focused on the growth and sheltering of juveniles and adults. This research provides valuable insights into the fishing management of a species that relies on diverse ecosystems for its life cycle.