Classification of Ovarian Stages of Alestes baremoze (Joannis, 1835): A Step towards Understanding Its Reproductive Biology

The indigenous Alestes baremoze is one of the fishes endemic to Lake Albert. In this study, the maturity stages of ovaries from 100 A.baremoze fish collected from Lake Albert were determined. Maturity condition was assessed by macroscopic inspection of gonads and histological methods. Macroscopic inspection was based on alterations in ovary size and appearance, whereas histological methods evaluated changes in oocyte stages. Gonado-somatic index (GSI) was used to assess the reproductive seasonality for a period of twelve months and was calculated as the proportion of ovary to body weight. Histological analysis confirmed the overall general appropriateness of macroscopic staging with stage IV being the most abundant in the samples and still the highest matching proportion between the two classifications. A correspondence graph obtained reveals few challenges in matching between macroscopic and microscopic classification for stages II and VI. Among ovaries macroscopically classified, 1% immature, 20% developing, 70% at spawning stage and 9% were at spent stage. The spawning pattern exhibited by A. baremoze indicate that this species undergo short spawning periods. This information is important in estimating maturity status which is a key in regulating A. baremoze fishery basing on spawning biomass.