Summary effect sizes for biomanipulations based on piscivore stocking and/or planktivore/benthivore removal. The diamond-shaped symbols show means of Secchi depth and chlorophyll a data from the selected set (with 95% confidence intervals indicated by the widths of the symbols). In the bottom row of each panel, data presented in the second and third rows have been pooled. Forest plots showing all individual effect sizes are presented in Additional file 10 (pp. 24–27). Subgroup means of potential effect modifiers (lake area, pre-manipulation total phosphorus concentration (TP) and fish quantities removed per hectare and year) are shown at right. These data were log-transformed before the calculation of means, and then back-transformed.