Effect of turbidity, prey density and culture history on prey consumption by greenback flounder Rhombosolea tapirina larvae

Fish larvae cultured in turbid “green water” conditions commonly show improved feeding, growth and survival, however, the underlying mechanisms remain unclear. Greenback flounder Rhombosolea tapirina (Günther) larvae, reared in either green water (Tetraselmis suecica, 5 NTU) or clear water tanks were used in short duration feeding trials to investigate the effect of larval culture history, live prey density (0.01–5 prey ml− 1), and turbidity level (0–40 NTU) on feeding performance. Prey consumption was density-dependent at prey densities below 0.1 ml− 1 and 0.05 ml− 1 for feeding on rotifers and Artemia, respectively. Green water reared larvae fed in green water consumed more rotifers across the range of prey densities tested compared with clear water reared larvae fed in clear water. At low prey density, where absolute performance capabilities of the larvae are tested, green water provided immediate improvement to rotifer intake at turbidity levels of 5–20 NTU for larvae with experience of either a clear or green water environment. However, larvae with experience of a green water environment outperformed larvae with experience of a clear water environment. Thus mechanisms that operate over the short term, such as contrast enhancement and chemical stimulation of feeding, as well as mechanisms that operate over the longer term, such as possible differences in retinal development, improvements in handling times and experience, are likely responsible for improved early larval performance in green water.