INFRASOUND PRODUCES FLIGHT AND AVOIDANCE RESPONSES IN PACIFIC JUVENILE SALMONIDS

A 10-Hz frequency sound caused flight or avoidance responses in juveni le spring Chinook salmon Oncorhynchus tshawytscha and rainbow trout O. mykiss. Groups of fish were placed in 3-m diameter circular tanks wit h a water depth of 1 m. The sound source was a 25-cm diameter aluminiu m tube with a piston in one end. The piston was driven back and forth by an eccentric coupling to an electric motor at a frequency of 10 Hz and with peak to peak amplitude of 4 cm. The sound source was turned o n for 5s when the fish was within 1 m. Initial tests always resulted i n a strong flight response, but after three to four tests the fish mor e typically simply swam away as far as possible from the sourer. This avoidance response did not habituate even after 20 trials. (C) 1997 Th e Fisheries Society of the British Isles.