Growth and reproduction of Donax trunculus from the Gulf of Annaba (Northeast Algeria) in relation to environmental conditions.

This study was aimed to evaluate the physiological reproductive end points (sex ratio, gametogenic cycle) and biological indices (condition index, length-weight relationship) in D. trunculus collected monthly over the year 2016, from two sites of the Gulf of Annaba (Northeast Algeria): El Battah (relatively unpolluted site) and Sidi Salem (polluted site). The results showed that gametogenesis takes place from December to August in both sites, with an autumnal resting phase. Also, the spawning occurred between March and August with two major spawning phases: April and August in El Battah vs May and August in Sidi Salem. The condition index showed a significant decrease in Sidi Salem site and positive correlation with gonad index. Moreover, the sites exert a significant effect on the allometric relationship and no significant effect on sex ratio. The observed reproductive events are discussed with the changes in the biological indices and the levels of pollution in the studied sites.