143 
Seasonal, diel, and lunar spawning periodicities 
and associated sound production 
of white seahass ( Atractoscion nohiBis ) 
Scott A. Aalbers 
Email address: scott@pier.org 
Hubbs-SeaWorld Research Institute 
2595 Ingraham Street 
San Diego, California 92109 
and 
California State University, Fullerton 
800 North State College Blvd. 
Fullerton, California 92634-9480 
Present address: Pfleger Institute of Environmental Research 
315 N Clementine 
Oceanside, California 92054 
Abstract — Spawning periodicities of 
white seabass (Atractoscion nobilis) 
were evaluated by observing spawning 
behavior, by collecting eggs, and moni- 
toring recognizable sounds produced 
during the release of gametes. A total 
of 297 spawning events were docu- 
mented from 15 male and 47 female 
white seabass contained within the 
seminatural confines of a 526-m 3 net 
pen located in Catalina Harbor, Santa 
Catalina Island, California. Consis- 
tent spawning occurred from March 
through July 2001-03, and peaked 
in May at a photoperiod of 14 hours. 
Most spawning occurred within the 
2-hour period following sunset or from 
19:00-20:00 hours Pacific Standard 
Time. White seabass spawned at 
every phase of the lunar cycle; but 
an increase in successive spawning 
events followed the new moon. Most 
spawning occurred in water tempera- 
tures from 15 to 18°C, and there was 
no apparent correlation with tidal 
cycles. Seasonal and diel spawning 
periods were directly correlated with 
increases in the rate, intensity, and 
variety of white seabass sounds; this 
correlation may indicate that sounds 
function to enhance reproductive suc- 
cess. These findings can be extended 
to further develop seasonal fishery 
regulations and to better comprehend 
the role of sound in the reproduction 
of sound-producing fishes. 
Manuscript submitted 13 September 2007. 
Manuscript accepted 10 January 2008. 
Fish. Bull 106:143-151 (2008). 
The views and opinions expressed or 
implied in this article are those of the 
author and do not necessarily reflect the 
position of the National Marine Fisheries 
Service, NOAA. 
The white seabass (Atractoscion nobi- 
lis), also known as white weakfish 
(Eschmeyer et ah, 1983), is an ovipa- 
rous group spawner; multiple males 
fertilize the eggs of a gravid female as 
gametes are broadcast into the water 
column (Aalbers and Drawbridge, 
in press). As the largest member 
of the family Sciaenidae (croakers 
and drums) that inhabits California 
coastal waters (Miller and Lea, 1972), 
white seabass produce relatively large 
eggs, averaging 1.27 mm in diameter 
(Moser et ah, 1983). Fertilized eggs 
are buoyant and drift with the ocean 
surface currents for two days before 
hatching into planktonic larvae that 
disperse for approximately 30 days 
and settle out nearshore at a size of 
7-10 mm (Moser et ah, 1983; Allen 
and Franklin, 1992). 
A previous study, in which the go- 
nads of commercially caught white 
seabass were examined, indicated 
that spawning occurs from April 
through August and peaks in May 
and June (Skogsberg, 1925). The ma- 
jority of white seabass have tradition- 
ally been landed in the late spring 
and early summer, when spawning 
aggregations develop nearshore and 
around coastal islands (Skogsberg, 
1939; Thomas, 1968). Following a 
sharp decline in California landings, 
the commercial harvest of white sea- 
bass was restricted from March 15 
through June 15 to protect spawning 
stocks, while recreational bag lim- 
its were reduced from three to one 
fish during this three-month period. 
Although current restrictions offer 
white seabass spawning aggregations 
some refuge, a better understanding 
of spawning periods will allow man- 
agers to further develop seasonal fish- 
ery regulations. 
Reproduction has been coupled 
with sound production in other spe- 
cies of Sciaenidae, including the red 
drum ( Sciaenops ocellata) (Guest and 
Lasswell, 1978), spotted seatrout (Cy- 
noscion nebulosis) (Mok and Gilmore, 
1983), weakfish (Cynoscion regalis ) 
(Connaughton and Taylor, 1995), and 
orangemouth corvina (Cynoscion xan- 
thulus) (Fish and Cummings, 1972). 
Typical of most sciaenids, male white 
seabass possess sonic musculature 
that resonates pulsed sounds from 
the adjacent gas bladder (Tavolga, 
1964). Although the sonic muscula- 
ture and gas bladder structures vary 
considerably among the 270 sciaenid 
species (Chao, 1986; Ramcharitar et 
ah, 2006), the sonic structures that 
Smith (1905) and Tower (1908) de- 
scribed a century ago in male weak- 
fish closely resemble those of white 
seabass. The importance of sound 
to this diverse family has been well 
documented during periods of repro- 
ductive activity (Ramcharitar et ah, 
2006); however, recognizable sounds 
during the actual release of gametes 
