HYDROACOUSTIC ESTIMATION OF THE NUMBER OF FISH PASSING THROUGH BEAUCAIRE-VALLABREGUES LOCK (RHONE)

Frequently used in sea and lake to study fish populations, the use of hydroacoustic methods in shallow waters is increasing. The number of f ish passing through Beaucaire-Vallabregues lock, first obstacle on the river Rhone, is estimated using a SIMRAD EY500 split-beam sounder, fr equency 70 kHz. Two transducers sample about 35 % of the lock's sectio n. For each lock cycle, the number of fish going across the lock is in dicated. The characteristics of the fish crossing (dates, position, ti me and delay) are shown. Current analyses do not permit to discriminat e the two main species which cross the lock, the shad (Alosa fallax) a nd the mullet (Mugil cephalus).