Specimens of Serrapinnus piaba were collected monthly from April 2001 to April 2002 in the rio Ceará Mirim, Rio Grande do Norte State, Brazil. The reproductive period, determined through the monthly variation of the gonadosomatic index (GSI) and maturation stages, occurred from January to April. Non-parametric Spearman test was performed in order to test correlation of monthly GSI variation in males and females with water temperature, rainfall and day length. Rainfall and Temperature were correlated with GSI variation in females only and day length showed a negative correlation with GSI variation of males only. It was verified the presence of hooks on the anal fin of mature and maturing males along all the period of study. The absolute fecundity mean was 441 (±178.08) oocytes, determined by the number of yolky oocytes counted in 27 mature female gonads. The relative fecundity, estimated by the number of yolky oocytes divided by milligram of total body weight was 0.74 (± 0.19).
reproduction; fin hooks; Neotropical; Cheirodontini
