2.2. Sampling and field data
The sampling strategy was based on previous studies that showed a good mixing of the water column (Lemonnier et al., 2010). One sampling station was representative of the whole pond. Thus, water sampling was carried out early in the morning (between 6 am and 8 am, local time) by the farmer at a station located near the pond discharge-gate. Sampling was scheduled three times a week over a period ranging from the 30th rearing day (d30) to the end of the rearing (d180). Surface water samples were collected using a 2-L polyethylene bottle. Procedures used in this study to measure water physico-chemical parameters (salinity, temperature, dissolved oxygen (DO), Secchi) have already been fully described in Lemonnier et al. (2006).