Reproductive biology of Turbo sarmaticus at Dwesa-Cwebe Nature Reserve
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The reproductive biology of giant periwinkle (Turbo sarmaticus) was investigated using gravimetric method. Samples were randomly collected from Dwesa-Cwebe Nature Reserve during spring low tide from June 1996 to July 1997 and preserved in 10% formalin seawater. A 2-way Analysis of Covariance (ANCOVA) test was used to test the effect of gender and month on the Gonado-Somatic Index (GSI) using the operculum diameter as covariate. The results indicated that the male GSI was grater than the female GSI and this was due to the selective predation. The results showed synchronized spawning period of both males and females. Results from Chi-squared tests showed a distortion from a 1:1 sex ratio with significantly more males than females. Males appeared to attain size at sexual maturity earlier than females. Spawning of T. sarmaticus occurred in warmer months and temperature was found to be the important factor triggering spawning. Information obtained from this study may possibly add value on the effective management of this species. Key words: Turbo sarmaticus, reproductive cycle, spawning period, sex ratio, sexual maturity.