Control of the migrating course of freshwater amphidromous shrimps by lighting

Field trials were conducted to examine the feasibility of guiding juvenile freshwater shrimps to fishways using lights at nighttime during the summer. The number of migrating shrimps was counted after different numbers and arrangements of underwater electric torches (wavelength 400-700 nm, narrow focus) were illuminated in the rivers. An underwater beam (2400-15000 lx) placed on the bottom and directed diagonally upstream across the river induced shrimps (e.g., Caridina japonica, C. leucosticta, C. typus, and Macrobrachium formosense) that were migrating along one bank to move across to the other side.