| seasonal reproductive biology of two species of freshwater catfish from the venezuelan floodplains. | oxydoras sifontesi and pimelodus blochii are seasonal breeder fish. spawn occurs once a year over a short interval of time, at the beginning of the rainy season. the gonadosomatic index (gsi), and plasma levels of steroid hormones of p. blochii and o. sifontesi were studied from fish samples, collected from the portuguesa river (portuguesa state, venezuela) in 1998 and 2004-2005, respectively. gonadal tissue samples were obtained and processed for histology. a macroscopic classification of the d ... | 2007 | 17416368 |