| 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 |
| spatial population structure of the neotropical tiger catfish pseudoplatystoma metaense: skull and otolith shape variation. | using geometric morphometrics, the skull and otolith of tiger catfish pseudoplatystoma metaense were analysed to identify population structure in tributaries of the apure river (i.e. the sarare, caparo, guanare, portuguesa and san carlos rivers) in the orinoco basin, venezuela. the analyses show uniformity in skull and otolith shapes of p. metaense within and among four tributaries, with only the caparo river showing significant differences. within the apure basin, the stock of p. metaense was d ... | 2013 | 23639147 |