Investigations on the sexual maturity, spawning and fecundity of king weakfish, Macrodon ancylodon, off the southern coast of Brazil (lat. 29º to 32ºS) were carried out from September, 1976, to August, 1977. The sex ratio varied monthly, with slight predominance of males (51.14%) over females (48.86%). The mean size at first maturity was estimated as 27.4 cm TL for females and 21.5 cm TL for males. The macroscopic examination of gonads and analysis of the gonadal index indicated that December and February were the most intensive spawning months. Fish weight proved to be the best predictor data of fecundity: F = 17056.2500 + 425.3712 Wt (r² = 0.6434) , were F is the total number of eggs in both ovaries. The number of eggs of 199 females varied from 59,850 for 33.4 cm TL fish to over 358,450 for 37.2 cm TL; the mean fecundity verified was 165,273 eggs per female. Frequency distributions of egg diameter in the ovaries were polymodal, suggesting fractional spawning during the reproduction season.
Sex ratio; Sexual maturity; Spawning seasons; Fecundity; Macrodon ancylodon; Brazil