Influence of wastewater treatment on the reproduction and growth of Mytilus galloprovincialis in Agadir's central Atlantic marine ecosystem, South Morocco.

Mytilus galloprovincialis is common in Morocco's Anza-Taghazout coast, previously polluted by wastewater. Since treatment plants were installed in 2016, no study examined the mussels' reproduction. Our study assessed how wastewater treatment affects the reproduction and growth of the M. galloprovincialis mussel on Moroccan coasts, particularly in the Anza-Taghazout area. We aimed to clarify the impacts of treated effluents on this vital invertebrate. This research explored their reproductive parameters, with samples taken from 2017 to 2018 at Anza, Aourir, and Imouran. Results show all gametic stages with three spawning periods. The gonadal index exceeds 1.4 at all sites, indicating a short resting phase. The sex ratio is balanced in Aourir and Imouran, but Anza has more males. The length-weight relationship showed the b value of 1.56 (R² = 0.32); 1.71 (R² = 0.35), and 1.70 (R² = 0.26) for Anza, Aourir, and Imouran respectively. This suggests a slight negative allometric relationship. The condition index showed a progressive trend, and M. galloprovincialis improved due to enhanced environmental quality after treatment. • Evaluation of the physiological reproductive parameters and condition index of M. galloprovincialis • Presence of all the gametic with three main spawning periods in the year • Gonadal index shows values >1.4 in the studied sites. • Sex ratio is balanced at the level of Aourir and Imouran. • Condition index experienced a progressive trend over the study period. [ABSTRACT FROM AUTHOR]