SMITH ET AL.: ORGANIZATION OF NEKTON 



PAR DEN 



81 160 



rPLA 



NEM 



NER 



CLS 



Na 



PAL 



TEL 



MOR AME 



21 160 



PLA 

 NER 



i-MISC 



CLS 



Na 



-AMP 



Lp 



GAM 



UID 



-COR 



28 28 



146 163 



Me 

 MISC 



TRI MAC 



2 1 I60 



NER 



CLS 



TEL 



UID 



DET 



MISC 



-CAP 



179 27 8 



ICTCAT 



8I 280 



r-NER 

 MAC 



126 158 



LEIXAN 



I6 I25 



PLA 



-CHL 

 FOR 



NEM 



-Eh 



NER 



MAL 



OLI 



-SPI 



CLS 



OST 



HA 1 



HA 2 



LP 



MISC 



J-CAL 

 La 



s 



CYA 



l-Me 

 DET 



1722 1753 



ANC MIT 



2I I00 



t — PI 



-BIV 



CRZ 



wr _ 



HA1 

 }-HA2 



CAL 



Na 



LP 



UID 



:-GAM 



242 330 



i-DET 

 MISC 



FIGURE 4. — Trophic comparisons among dominant predators ( those comprising > 98% of the total number of individu- 

 als captured), pooled across all sampling strata. PAE DEN = Paralichthys dentatus; MOR AME = Morone 

 americana; TRI MAC = Trinectes maculatus; ICT CAT = Ictalurus catus; LEI XAN = Lewstomus xanthurus; ANC 

 MIT = Anchoa mitchilli. Ratios appearing below histograms represent stomachs with food as a proportion of total 

 stomachs. Values above histograms are size ranges (standard lengths). Diet composition was compared using Can- 

 berra metric and unweighted-pair group-average clustering strategy, data untransformed. Prey designations are 

 defined in Table 4. 



TABLE 4. — Prey categories used for trophic comparisons. All 

 but unidentified (UID) and miscellaneous (MISC) are mutually 

 exclusive feeding categories. 



Among the six species examined, spot and bay 

 anchovy displayed the least dietary overlap, with 

 the former exhibiting the greatest dietary diver- 



sity (consisting mainly of benthic prey items), and 

 the latter including a greater percentage of plank- 

 tonic food items in its diet. However, the large 

 variety of prey items consumed by all species indi- 

 cates that each is a trophic opportunist (Darnell 

 1958, 1961; Carr and Adams 1973; Sheridan and 

 Livingston 1979; Livingston 1982). 



Ontogenetic shifts in diet were evident for each 

 of the species examined (Fig. 5). In spot, dietary 

 importance of calanoid copepods declined in fish 

 >20 mm SL, while harpacticoid copepods in- 

 creased in importance in fish 21-80 mm SL. Con- 

 currently, the percentage of various polychaetes 

 and gammarid amphipods slowly increased in 

 their diet. Nematodes also became less important 

 with increasing size. Interestingly, spot stomachs 

 at all sizes contained clam siphons and maldanid 

 tails, indicating that specific parts of larger prey 

 were important dietary items. 



Ostracods and crab zoea were abundant food 

 items for small (<21 mm SL) bay anchovy; larger 



461 



