Life-history aspects of Bryconamericus microcephalus (Miranda Ribeiro, 1908) from córrego Andorinha (23º11'12"S, 44º12'02"W) were assessed throught the length structure, length-weight relationship and reproductive strategy. Specimens were bimonthly sampled, between November 1999 and September 2003, through waiting nets and "picarés" (mesh size between 0,5 and 1,0 cm). Length structure showed that females attain bigger sizes then males and that higher number of females was registered for the length classes bigger than 5.3 cm. Length-weight relationship showed significant differences between sexes and indicates that, for individuals of the same size, females are weightier than males. Sex ratio was 2.2:1 (female: male). Size at first maturation was 4.2 cm without differences between sexes. Reproductive specimens were registered from July to February with the reproductive pike occurring from September to December without differences in the reproductive pattern of specimens belonging to two different standard length classes. Mean values of gonadosomatic index of ripe females of the same two standard length classes indicated that the reproductive investment are higher among bigger individuals. High values of fecundity (F) were registered varying from 408 to 1025 oocytes for fish of 5.4 and 7.0 cm respectively. Relationship between weight and number of oocytes/g was positive and indicated that bigger specimens produced more oocytes.
Fishes; reproductive strategy; sexual dimorphism; seasonality
