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Fishery Bulletin 96(2), 1998 
single larva (stage I, 13.8 mm SL) clearly demon- 
strated benthic feeding, having ingested polychaete ten- 
tacles and harpacticoid copepods, and the other larva 
had ingested a mysid, a taxon noted for diurnal migra- 
tions (Newell and Newell, 1977). All late-stage larvae 
in estuarine collections displayed noticeably darker pig- 
mentation than was observed in earlier stages. 
incidence of feeding in estuaries 
A comparison of the incidence of feeding of oceanic 
and estuarine summer flounder larvae was limited 
to nocturnal collections and revealed strikingly dif- 
ferent patterns (Table 1; Fig. 4). Between 1800 and 
0759 hours the incidence of feeding of estuarine lar- 
vae never exceeded 20.0%, whereas values for oce- 
anic larvae ranged from 8.3% to 84.4%. The greatest 
differences between oceanic and estuarine larvae 
were observed early in the night: at 1800-1959 and 
2000-2159 the incidence of feeding in estuarine col- 
lections was significantly lower than in oceanic col- 
lections (P<0.01, x 2 =33.78, 1 df, at 1800-1959; 
P<0.01, % 2 =30.99, 1 df, at 2000-2159) (Fig. 4). Be- 
cause most (63.0%) larvae in estuarine samples were 
collected between 1800 and 2159 (Table 1), these com- 
parisons were not biased by low sample size. 
Within estuarine habitats, incidence of feeding 
declined with metamorphic stage, from 19.1% at 
stage G to 2.9% at stage H (Table 1). Time was not a 
factor in this decline because the distribution of lar- 
vae of stages G, H-, and H was the same across early- 
(1800-2159), mid- (2200-0159), and late-night (0200- 
0559) collections (P=0.18, % 2 =6.22, 4 df). 
Discussion 
The diet of all stages of oceanic summer flounder lar- 
vae was dominated by immature copepodites in the 
NW Atlantic Ocean. The size of other ingested prey 
was directly related to larval size. Small prey items 
such as copepod nauplii, tintinnids, and bivalve lar- 
vae, were important only in the diet of early (PF) 
stage larvae. Large prey items, such as adult calanoid 
copepods and appendicularians were important only 
in the diet of later (PM and M) stage larvae. 
The diet of metamorphosing (ME) larvae that were 
collected in a New Jersey estuary was dominated by 
the calanoid copepod Temora longicornis. 
These observations differ sharply from the diet of 
metamorphosing larval summer flounder in a North 
Carolina estuary (Burke, 1995). Burke (1995) re- 
ported that the larval diet was dominated by poly- 
chaetes and mysids. However, all larvae in the North 
Carolina study (Burke, 1995) were caught in estua- 
rine nursery areas with benthic trawls, whereas in 
the present study oceanic larvae were caught with 
bongo nets, and estuarine larvae were caught with 
stationary plankton nets. Clearly these two studies 
captured metamorphosing larvae during different 
ecological phases of the transition from pelagic to 
benthic ecology. The diet of late-stage metamorphic 
larvae that demonstrated benthic 
feeding in an estuarine habitat in the 
present study was similar to the diet 
of comparable size larvae in Burke’s 
(1995) study. The darker pigmenta- 
tion of benthic-feeding, late-stage lar- 
vae suggests that this pigmentation 
may be a valid marker of adaptation 
to the benthic habitat in summer 
flounder, as has been observed in other 
species (Grover et al., in press). 
The pelagic diet of a congener, the 
olive flounder, 3 Paraliehthys olivaceus, 
may represent a more cogent com- 
parison. In Wakasa Bay in the Japan 
Sea, Minami (1982) reported that 
3 The common and scientific names of fish spe- 
cies used in Fishery Bulletin are those recom- 
mended by the American Fisheries Society 
(Am. Fish. Soc. Spec. Publ. 20, 5th ed., 1991). 
The following names have been changed ac- 
cordingly: Japanese flounder to olive flounder; 
Parophrys vetulus to Pleuronectes vet ulus', 
Isopsetta isolepis to Pleuronectes isolepis\ and 
Linxanda ferruginea to Pleuronectes ferrugineus. 
Estuarine 
Oceanic 
Onset of time block 
Figure 4 
Incidence of feeding of larval summer flounder, P. dentatus, in the NW Atlantic 
Ocean and in a New Jersey estuary, as a function of time of day (EST) through 
the night. Data are based on a total of 331 oceanic and 119 estuarine specimens. 
