This study analysed the reproductive biology of the tambaqui Colossoma macropomum in the Lower Amazon. 1232 individuals were collected from October 1994 to February 1996 from landings in Santarém in Pará State. Individuals between 20 and 120cm total length were weighted, measured, sexed and classified according to their maturity stage. Fecundity and spawning type were determined to analysing intra-ovarian oocytes of 10 adult females. Colossoma macropomum is a total spawner. There are changes at different levels: macro and microscopic cycles according to hydrological periods. Mature individuals occurred between november and february, indicating that spawning take place during this period, at the beginning of flood. The sexual rate changes with the size of fishes. Males are more frequent between 40 and 75cm, and the females between 80 and 115cm. The length/weight relationship indicates differences in the growth between males and females. The average fecundity was estimated on 1.007.349 eggs per female. There is a significant relationship between fecundity and total weight. The equation founded to tambaqui in the Lower Amazon was F = 885347 + 9,16 W1.
Amazonian; Colossoma macropomum; reproduction; spawning; fecundity