ABSTRACT. REPRODUCTIVE INDlCES FROM SPECIES OFspi/opterus Günther, 1862, are the most common flatfishes found in Guaratuba Bay, south Brazil. Different size categories of these flatfish occur in the mangrove area throughout the year. The Gonadosomatic Index, the Condition Factor, and the morphological analyses of the gonads from samples obtained between 1994 and 1996 revea1s aspawning activity during late Spring and early Summer. This period coincides with the increase in temperature and decrease in sa1inity. Spawning evidence and the presence of ali size categories throughout the year indicate that Cilharichlhys spp. are permanent inhabitants of the mangrove in Guaratuba Bay, where they complete their life cycle.