Aspects of the life history of the Silver Cyprinid Rastrineobola argentea (Pelligrin 1904) (Teleostei: Cyprinidae)

Rastrineobola argentae, commonly known as the silver cyprinid, it is a protogynous diandric teleost fish endemic to Lake Victoria in East Africa. R. argentea is a small, fast-swimming fish rarely reaching a length of greater than 8cm in standard length. Its body is slender and compressed. The fish is very hardy and reproduces all year round making it a good candidate for studying developmental processes. Following the introduction of exotic and predatory fish in the 1950’s in Lake Victoria, the silver cyprinid is one of the endemic fish species that has remained unaffected. The lake is now dominated by three fish species; Lates niloticus. an introduced predator; Oreochromis niloticus, an exotic herbivore and Rastrineobola argentea, an indigenous zooplanktivore. The purpose of this work was to to obtain information on age, growth and to describe oocyte developmental stages in the silver cyprinid, Rastrineobola argentea inhabiting the Nyanza Gulf of lake Victoria and relate this information to the reproductive biology of the species. Fish were sampled, fixed and processed for histology using standard histological procedures. The current study has revealed that there is a positive correlation between length and mass of Rastrineobola argentea and state of gonad development. Stages of oocyte developmental stages are similar to those described for other teleosts fish. Gonads were classified into three reproductive states: immature, maturing and mature. All fish sampled in this study were females except in size class G (> 50 mm Total length) where males were predominant. Explanation as to why males were only seen in this size class could not be determined from the results of the study.