Campfield and Houde: Ichthyopiankton community structure and comparative trophodynamics 
5 
two most abundant species, naked goby and white 
perch. In 2000, their mean combined-species CPUE 
increased directionally from freshwater to oligohaline 
regions (Appendix Table 1). In contrast, in 2001 their 
combined mean CPUE was highest at the salt front, in- 
termediate in freshwater, and lowest in the oligohaline 
region (Appendix Table 2). 
Occurrences and abundances of larvae of anadro- 
mous species differed with respect to location of the 
salt front. Yolk-sac larvae of striped bass occurred 
most frequently up-estuary of the salt front in tidal 
freshwater, whereas most feeding-stage larvae and 
small juveniles {<75 mm) were found either within or 
up-estuary of the salt front. White perch larvae were 
broadly distributed throughout the estuarine transition 
zone, overlapping with alosines (mostly alewife) and 
congeneric striped bass. 
Larvae of alewife were consistently most abundant 
up-estuary of the salt front (Fig. 4). In 2001, larval 
white perch were clearly more abundant in freshwater 
than at the salt front or down-estuary, but in 2000 
they were equally abundant at the salt front and in 
freshwater. Larval striped bass concentrations did not 
differ significantly among the three regions (P> 0.08) or 
between 2000 and 2001 (P>0.07), although their num- 
bers tended to be relatively high at the salt front and 
in freshwater in 2001 (Fig. 4). 
Temporal patterns in abundances of alewife, striped 
bass, and white perch were broadly similar in both 
years. Abundance of white perch larvae was an order 
of magnitude higher than striped bass in the earli- 
est seasonal collections in each year and generally 
was higher than that of striped bass throughout the 
survey periods (Fig. 5). Although larval naked goby 
were present earlier in the season during 2001, their 
abundance peaked in the second week of June in both 
years (Fig. 5), when temperatures in the oligohaline 
region reached 25°C. 
In each year, catches of larvae and small juveniles of 
the estuarine- and coastal-spawning species became in- 
creasingly common later in the sampling period. Small 
juveniles of menhaden and bay anchovy dominated the 
late-season (June and July) collections in Tucker trawls. 
Naked goby larvae occurred first in the oligohaline 
