The acoustic behavior of Southern King Weakfish (Macrodon atricauda-Sciaenidae)

Many species of fishes use acoustic signals for a variety of purposes, and sciaenid are well-known producers of sound. The Southern King Weakfish (Macrodon atricuada- Sciaenidae) possesses sexually dimorphic bilateral sonic muscles used for sound production. The bilaterally paired muscles lie on the inner body wall of the male, surrounding the swimbladder. The Southern King Weakfish produces three different sounds: advertisement calls, disturbance calls and dual-knocks, these sounds were recorded from Rio de la Plata estuary, Uruguayan coastal waters and laboratory. The advertisement call, related to courtship, was recorded in the field and from spawning males in the laboratory. Disturbance calls were produced when captive M. atricauda were startled, chased with a net or grabbed by the tail. Disturbance calls consist of a burst of pulses produced at short intervals. In disturbance call interpulse interval increased and dominant frequency decreased linearly (P < 0.05), pulse duration did not change with fish size. M. atricauda start producing disturbance call at 14 cm LT (Total Length), but only individuals over than 25 cm LT were who produced the advertisement call. Dual-knocks, call compose of only two pulses together, was recorder only in captivity. Sounds are a valuable non-invasive tool for fisheries biologists can used to monitor on males in spawning populations.