12 
Fishery Bulletin 109(1) 
fjra diatoms 
l l invertebrate eggs 
I I rotifers 
2000 
tVsl copepod nauplii 
I I cyclopoids 
ri Bosmina 
Eurytemora 
Acartia 
No. of prey/stomach 
2000 
CO 
E 
o 
0 0 
Q) 
> 
CD 
QC 
2001 
Alosa pseudoharengus 
O in N O) a 
co in n A 
co m n o) o) 
co in n A 
Morone saxatilis 
salt front 
oligohaline 
salt front 
oligohaline 
100 
80 
6C 
40 
20 
(T 
100 ‘ 
80 
60 
40 
20 
0 
I 
2001 
(3) (4) (4) (6) (6) (6) 
(10)(11)(10)(11) 
“Tprcfra 
(10)(12)(10)(8) (7) 
in CD N CO O) o 
4 in (D n co T 
Gobiosoma bosc 
2000 
80 ' 
2001 
freshwater 
o 
loot 
80 - 
60 - 
40 
20 
0- 
10G| 
80 
60 
40 
20 
0- 
■i 
: 
i 
if 
(4) (4) (6) (4) 
p) m n O) 
4 n if) n 
Morone americana 
Larval length (mm) 
Figure 8 
Relative stomach content (% by numbers; bars) and total stomach content (number of prey per stomach; lines) for 2-mm 
length classes of alewife ( Alosa pseudoharengus) larvae (all sampled larvae were from freshwater stations), for 2-mm 
length classes of striped bass ( Morone saxatilis ) and white perch ( Morone americana) larvae from freshwater, salt-front, 
and oligohaline stations, and for 1-mm length classes of naked goby (Gobiosoma bosc ) larvae from salt-front and oligo- 
haline stations. The number of larvae analyzed is shown in parentheses. 
on continental shelves, where taxa in coastal and oce- 
anic assemblages frequently have quite distinct distri- 
butions (Richardson et ah, 1980; Young et al., 1986; 
Munk et ah, 2004). In estuaries, gradients in larval 
and juvenile fish assemblages, often with overlaps, 
and seasonal shifts in taxonomic dominance are typi- 
cally explained by salinity and temperature regimes 
(Rakocinski et ah, 1996; Witting et ah, 1999; Martino 
and Able, 2003) and this appears to be the case in the 
Patuxent River. 
Strong gradients in water mass properties, especially 
temperature and salinity, combined with complex circu- 
lation processes at hydrographic fronts can act as hy- 
drodynamic particle traps and provide favorable forag- 
ing habitat for fish larvae (Nakata et ah, 1995; Munk, 
1997; Hillgruber and Kloppmann, 1999; North and 
Houde, 2003; Islam and Tanaka, 2005). In estuaries, 
temperature and salinity often are the most important 
variables delineating ichthyoplankton distributions. As 
examples, in the St. Lucia estuary, South Africa, tem- 
