The white seabass is the largest of the 10 species in the family Sciaenidae (croakers and drums) known to occur in California coastal waters, and can reach a size of over 5 feet and about 95 pounds. White seabass are broadcast spawners, with multiple (2-7) males simultaneously releasing gametes to fertilize the eggs of a spawning female within the water column (Watch video of a broadcast spawning event). The white seabass spawning season occurs from March through July and peaks in May, with the majority of spawning events occurring over the 2-hour period following sunset (Aalbers, 2008). A nighttime spawning strategy is typical of other temperate fishes, and has been proposed as a means to reduce initial egg predation.
Like most croakers, only male white seabass produce sounds by contracting specialized muscles that are located along the abdominal wall. When the sonic musculature contracts it causes the swim bladder to resonate which produces a low frequency sound. Female white seabass lack this specialized structure and hence do not have the ability to produce the low frequency sound.
Sound production has been associated with reproduction in other croaker species, including the red drum (Sciaenops ocellata), spotted seatrout (Cynoscion nebulosis), weakfish (Cynoscion regalis) and orange-mouth corvina (Cynoscion xanthulus). However, white seabass are the only croaker species known to produce a distinct series of pulsed sounds (spawning chant) during the release of gametes (Aalbers and Drawbridge, 2008). Numerous fish species have developed effective sound producing and detection mechanisms to take advantage of the high speed and distance of sound propagation underwater. Sound production apparently supports the development of spawning aggregations and may aid in the simultaneous release of gametes during broadcast spawning events after dark.