Biomanipulation of fish assemblages as a lake restoration technique

We searched the limnological literature to assess the success of biomanipul ation projects with respect to improvement of water quality in culturally e utrophic lakes and reservoirs. We reviewed 41 biomanipulation experiments ( from 63 published papers/books) involving the reduction of zooplanktivorous and benthivorous fish abundances in 39 lakes. We divided the experiments i nto five categories based on the type of biomanipulation performed: piscivo re stocking, piscivore stocking + partial fish removal, partial fish remova l, elimination of fish, and elimination of fish followed by restocking. We judged success (consistently successful, partially successful, unsuccessful ) by changes in water quality variables; primarily phytoplankton or chlorop hyll biomass and water transparency, during the post-implementation period of each study. The percentage of consistently successful manipulations vari ed with approach: piscivore stocking (28.6 %), piscivore stocking + partial fish removal (60.0 %), partial fish removal (90.0 %), elimination of fish (40.0 %), and elimination of fish followed by restocking (66.7 %). Overall, 61 % of the biomanipulations were consistently successful in improving wat er quality, with most successful attempts involving small, shallow lakes (< 25 ha, mean depth < 3 m). Only 14.6 % of the biomanipulations were unsucce ssful in improving water quality for at least one year. Biomanipulations re sulting in increased abundances of Daphnia and macrophytes were most likely to achieve stable clear water states and maintain improved water quality.