Donohoe: Age, growth, distribution, and food habits of Atractoscion nobilis 
717 
Age (d) 
Figure 8 
Gompertz growth curves relating (A) length and age, and (B) weight and 
age of recently settled white seabass. Ages were determined from counts of 
increments in sagittae. 
depth contour than along the 10-m con- 
tour (Allen and Franklin, 1992). Al- 
though this distribution supports the 
conclusion that white seabass prefer 
shallow water, 30-40% of the settled 
fish were caught at the 10-m contour 
(Allen and Franklin, 1992). Most of the 
fish collected at 10 m were taken along 
one section of coastline between Ven- 
tura and Point Dume; thus the prefer- 
ence for shallow water may be modified 
by local conditions. 
Greater densities of settled fish along 
the open coast than in the bays suggests 
that the primary nursery for white 
seabass is the open coast. However, this 
difference in densities may reflect lower 
capture efficiencies of the 1.0-m trawl 
and beach seine in comparison with the 
1.6-m trawl used on the coast. Although 
net efficiencies could not be estimated 
for white seabass because of low abun- 
dance, Kramer ( 1990) found no difference 
in efficiency of these same nets for Cali- 
fornia halibut <40 mm SL. Net efficien- 
cies probably did not differ greatly for 
small white seabass either, and thus the 
low catch of settled fish in the two bays 
was due to low abundance. In ichthyofau- 
nal surveys of other southern California 
bays over the last several decades, only a 
few early juvenile white seabass have 
been caught (Dixon and Eckmayer, 1975; 
Klingbeil et al., 1975; Horn and Allen, 
1981). Although depths of 0-1 m may not 
have been sampled intensively, data from 
these surveys support the view that bays 
as a whole are not important nurseries 
for white seabass. 
The small size of southern California bays must 
also limit their importance as nursery areas for white 
seabass. As an example, Kramer (1990) estimated 
there were only 92 ha of habitat available between 0 
and 1 m in Mission Bay and only 10 ha in Agua 
Hedionda Lagoon, compared with roughly 2,500 ha 
of habitat available between 5 and 8 m along the coast 
of San Diego County. Most of the remaining bays on 
the southern California coast are also small and 
many are periodically closed off from the sea by shift- 
ing sandbars (Zedler, 1982). 
Nursery features 
The narrow depth distribution of settled white sea- 
bass along the coast suggests that one or more fea- 
tures of this zone enhance survival of young fish. Sur- 
vival in shallow nurseries may be higher because of 
faster growth resulting from abundant food or 
warmer water, or lower predation rates (Bergman et 
al., 1988; Karakiri et al., 1989). Two features of the 
white seabass nursery that may promote rapid 
growth of juveniles are the abundant mysids and 
warmer water. Mysids, the principal prey of all sizes 
of white seabass collected, appear to be much more 
abundant within the nursery than at adjacent 
depths. Clutter (1967) sampled mysids at depths of 
2-14 m during 1960-62 at a site 3 km south of the 
Torrey Pines 2 site (Fig. 1). Although the center of 
the depth distribution varied among months by 1-2 
m, the mysid Metamysidopsis elongata was most nu- 
merous in the middle of the white seabass nursery 
