The reproductive biology of Iheringichthys labrosus (Lütken, 1874) was studied in Furnas reservoir, Minas Gerais, Brazil. The fishes, 323 males and 817 females, were captured bimonthly from August 1993 to July 1994 by using gill nets with 3-10 cm mesh size. Gonadal maturation of the specimens was analyzed through macro and microscopical characteristics of the gonads. The secretory activity of the tubules of the caudal region of the testis was analyzed during the maturational testicular cycle. Females and males were in reproductive activity throughout the year in the reservoir. The peak of advanced maturation/mature stages occurred from October to January and of spawned/spent from February to May. The spawning of I. labrosus was identified as fractional or multiple type: occurring in the reservoir or in tributaries around it. The oocyte development of the species was asynchronous as different clusters of oocytes occurred simultaneously in the ovarian parenchyma. The epithelium of the tubules of the caudal region of the testis was in high secretory activity during advanced maturation/mature stage and this activity was absence in resting. The gonadosomatic index followed gonadal maturation, and the hepatosomatic index of females was lowest in advanced maturation/mature probably due the contribution of the liver in the vitellogenesis. The variations of the stomach repletion index, coelomic fat and condition factor indicated that the feeding activity was reduced and that the energetic reserves were consumed during the reproductive period.
Gonadal maturation; Pimelodidae; spawning
