Mean fish biomass and density measured in the layer between 0 and 3 m (D) and in the layer deeper than 3 m (S) sampling in three zones (u = upstream; m = middle; and d = downstream) of the Joumine Reservoir sampled in four seasons. The white bars correspond to day surveys and black bars correspond to night surveys. Error bars show standard deviations. Seasons are shown in each panel, abbreviated as follows: spring = S, summer = SU, Autumn = A and winter =W. Values between brackets represent mullet's biomass.