White seabass spawning behavior and sound production

White seabass Atractoscion nobilis (family Sciaenidae) form transient spawning aggregations in the spring and summer throughout southern California and northern Baja California, Mexico. Although spawning activity has been linked with sound production in other sciaenid fishes, the function and acoustic characteristics of white seabass sounds have not previously been identified. We described the spawning behavior and characterized the sounds generated by 62 white seabass maintained within the seminatural conditions and free-field acoustic environment of a net-pen moored in Catalina Harbor, California. In addition to visual observations, video and audio recordings were made during periods of peak spawning activity in 2001-2003. The physical characteristics of white seabass sounds were described and illustrated with sonogram, waveform, and power spectrum displays. Gravid females were identifiable during courtship and spawning by shifts in behavior and the development of dark bars across the dorsal region. During spawning, 1-9 males tightly surrounded a gravid female and the resultant pack shuddered in unison as gametes were simultaneously broadcast into the water column. Five distinct types of sound were produced by white seabass: single and multiple pulse trains during courtship, drumrolls and thuds during spawning, and booms during yawning and burst swimming. During the actual release of gametes, a rapid succession of overlapping drumroll and thud sounds resulted in identifiable spawning chants lasting 7-55 s. Consistent physical, behavioral, and acoustical patterns during courtship and spawning indicated that white seabass utilize visual, tactile, and sonic cues to communicate their reproductive state.