Individual study: Pyrotechnics are effective, but flashing lights and Scarey Man are ineffective in deterring herons from trout raceways at Watson Lake Fish Rearing Unit, Colorado, USA
Andelt W.F., Woolley T.P. & Hopper S.N. (1997) Effectiveness of barriers, pyrotechnics, flashing lights, and Scarey ManÂ® for deterring heron predation on fish. Wildlife Society Bulletin, 25, 686-694
This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.
Use netting to exclude fish-eating birds
A before-and-after trial in trout farms in Colorado, USA, in 1990-2 (Andelt et al. 1997), found that 7 cm nylon netting significantly reduced great blue heron Ardea Herodias numbers next to ponds, but they stayed longer to capture fish after netting installation. Netting was 2.3 m long, 0.5 m high and slanted toward the water. The effects of various scaring devices is discussed in ‘Scare birds from fish farms’.
Scare birds from fish farms
A series of before-and-after trials in trout farms in Colorado, USA, in 1990-2 (Andelt et al. 1997), found that pyrotechnics were effective at decreasing the number of black-crowned night-herons Nycticorax nycticorax and great blue herons Ardea herodia at farms. Firing pyrotechnics for 14 consecutive nights was more successful than doing so for seven nights. Frightening every fifth night was unsuccessful. Rotating lights did not reduce the number of attempted or successful fish captures. ‘Scarey Man’ reduced heron numbers during the first four nights but numbers of both species subsequently increased substantially to night 18, indicating habituation.