8 
Fishery Bulletin 109(1) 
Striped bass larvae primarily consumed relatively 
large zooplankters ( Eurytemora , Acartia, and Bosmina', 
Fig. 8), with no obvious ontogenetic shift in prey size. 
Calanoid copepodites and adults were the dominant 
prey of striped bass larvae down-estuary of the salt 
front. In the salt-front and freshwater regions, Bosmina 
was common prey of 11-19 mm larvae. Acartia was 
eaten by >ll-mm striped bass only in year 2000 and 
only in the oligohaline region. 
Diets of small white perch larvae were relatively di- 
verse, but larger larvae fed predominantly on Bosmina 
and the calanoid copepods Eurytemora and Acartia (Fig. 
8). The calanoid copepods were dominant prey down- 
estuary of the salt front. As for striped bass, Acartia 
was eaten by white perch only in 2000. 
Naked goby larvae had the least diverse diet. In the 
oligohaline region, they fed almost exclusively on cope- 
pod nauplii and calanoid copepods, including Acartia, 
in both years (Fig. 8). In the salt front region, the diet 
of goby larvae was more diverse. 
Prey utilization, preference, and importance 
Mean prey size increased with larval length and onto- 
genetic state in alewife, white perch, and naked goby, 
but not in striped bass (Table 2). Functional relation- 
ships between prey ingestion and either larval size or 
ontogenetic state differed among taxa. Niche breadth 
(standard deviation of mean logarithmic prey size) 
increased significantly in naked goby with respect to 
larval length or ontogenetic state, but not in the other 
species. 
Larval prey preference and importance differed 
among the three regions of the estuarine transition 
zone and were generated primarily by prey avail- 
ability and larval sizes. In general, Eurytemora was 
a preferred and important prey, especially for the 
moronid larvae and for large alewife larvae ( > 10 
mm) (Table 3A). Bosmina was an important prey 
across taxa and larval sizes, but was only preferred 
by large white perch larvae and large striped bass 
larvae in the salt-front region. Rotifers and cyclo- 
poid copepods were eaten, but were neither posi- 
tively selected nor important prey for larvae of the 
four species. In the oligohaline region, Acartia was 
positively selected by naked goby and large (>10-mm) 
white perch larvae. Copepod nauplii were positive- 
ly selected and important prey for small (<10-mm) 
alewife and naked goby larvae but were generally 
neither selected nor important for white perch and 
striped bass. 
Overall, diets of large (>10-mm) larvae strongly 
overlapped among taxa (0 = 0.88-0.90). Diet overlaps 
among larval taxa and sizes were strongest in the 
freshwater region (Table 3B). However, the diet of 
small alewife in freshwater did not overlap signifi- 
cantly with diets of other taxa or size classes. At the 
salt front, the only significant overlap in diets of larval 
fish was between naked goby and small white perch 
(Table 3B). In the oligohaline region, diet overlap was 
