In many soniferous fishes, males use nocturnal mating calls to attract females, resulting in characteristic mating choruses dominating estuary and ocean soundscapes. Multiple fish calling at the same time increases the range over which the calls can be detected by females, serving then as an “acoustic beacon.” Here, the onset of synchronous calling in males of the weakfish, Cynoscion regalis (Family Sciaenidae), is reported. Power spectral band (PSB) sums were evaluated across the frequency range 300–600 Hz, which is a characteristic frequency band for weakfish calls. PSB sums show a wave-like periodic variation before, during, and after sunset. The fish form synchronized choruses, which are visible as waves in the PSB sums. The period of the waves of PSB sums of the weakfish calls is about 2.6 s before sunset and decreased to 2.3 s in a post-sunset chorus as more weakfish began to call.